Download As化学汉英双解讲义

AS 无机化学讲义
主编
吴梓桢
北京市梓桢 A—level 培训中心 （创于 2004）
打造专业 A—Level 课外培训机构 & 公司自编经典学习资料
Preparation for As Chemistry
中国学生在学 AS 前要回忆的依然有用的初中化学知识
1 Symbols and names of elements
元素的名称与符号
Aluminium Al 铝
Germanium
Ge 锗
Antimony
Sb 锑
Gold
Au 金
Argon
Ar 氩
Helium
He 氦
Arsenic
As 砷
Hydrogen
H 氢
Barium
Ba 钡
Iodine
I 碘
Beryllium Be 铍
Iron
Fe 铁
Bismuth
Bi 铋
Krypton
Kr 氪
Boron
B 硼
Lead
Pb 铅
Bromine
Br 溴
Lithium
Li 锂
Caesium
Cs 铯
Magnesium
Mg 镁
Calcium
Ca 钙
Manganese
Mn 锰
Carbon
C 碳
Mercury
Hg 汞
Chlorine
Cl 氯
Neon
Ne 氖
Chromium
Cr 铬
Nitrogen
N 氮
Cobalt
Co 钴
Oxygen
O 氧
Gpper
Cu 铜
Phosphorus P 磷
Fluorine
F 氟
Platinum
Pt 铂
Francium
Fr 钫
Polonium
Po 钋
Gallium
Ga 镓
Potassium
K 钾
Radium
Ra 镭
Radon
Rn 氡
Rubidium
Rb 铷
Selenium
Se 硒
Silicon
Si 硅
Silver
Ag 银
Sodium
Na 钠
Strontium
Sr 锶
Tin
Sn 锡
Titanium
Ti 钛
Tungsten
W 钨
Uranium
U 铀
Vanadium
V 钒
Xenon
Xe 氙
Zinc
Zn 锌
2 前 20 号元素
3 金属活动顺序表
K Ca Na Mg Li Zn Fe Sn Pb H Cu Hg Ag Pt Au
4 中国的初三知识
(1) reactions between acids, bases,salts
酸
碱
盐
反应
(2)复分解反应条件(↑↓H2O 生成)
(3)盐的溶解性口诀：钾钠铵，硝酸溶，硫酸去铅钡，盐酸去银汞，其他都不溶。
(HCO3-盐一定可溶)
常见强酸：HCl、H2SO4、HNO3、H3PO4.(强酸和中强酸)
常见强碱：NaOH、KOH、Ba(OH)2、Ca(OH)2.(强碱和中强碱)
Chapter 1 Moles and equations
Content
I Relative masses of atoms and molecules
II The mole, the Avogadro constant
III The determination of relative atomic masses, Ar , and relative molecular masses, Mr , from
mass spectra
IV The calculation of empirical and molecular formulae
V Reacting masses and volumes (of solutions and gases)
Learning outcomes
The term relative formula mass or Mr will be used for ionic compounds
Candidates should be able to:
(a) define the terms relative atomic, isotopic, molecular and formula
masses, based on the 12C scale
(b) define the term mole in terms of the Avogadro constant
(c) *analyse mass spectra in terms of isotopic abundances and molecular fragments [knowledge of
the working of the mass spectrometer is not required]
(d) calculate the relative atomic mass of an element given the relative
abundances of its isotopes, or its mass spectrum
(e) define the terms empirical and molecular formulae
(f) calculate empirical and molecular formulae, using combustion data
or composition by mass
(g) *write and/or construct balanced equations
(h) perform calculations, including use of the mole concept, involving:
(i) reacting masses (from formulae and equations)
(ii) volumes of gases (e.g. in the burning of hydrocarbons)
(iii) volumes and concentrations of solutions When performing calculations, candidates’
answers should reflect the number of significant figures given or asked for in the
question. When rounding up or down, candidates should ensure that significant
figures are neither lost unnecessarily nor used beyond what is justified (see also
Practical Assessment, Paper 31/32, Display of calculation and reasoning)
(i) deduce stoichiometric relationships from calculations such as those in (h)
1.1 definitions
1) relative atomic mass, Ar, of an element is the weighted average mass of an atom of
the element relative to the mass of an atom of carbon-12, which has a mass of
exactly 12. 是比值无单位 unit
2) relative formula mass the weighted average mass of the formula of a compound
relative to an atom of carbon-12, which has a mass of exactly 12.
3) relative molecular mass the weighted average mass of a molecule of a compound
relative to an atom of carbon-12, which has a mass of exactly 12.
=
4) relative isotopic mass the mass of an isotope of an atom of an element relative to
an atom of carbon-12, which has a mass of exactly 12.
1.2 Finding relative Atomic mass
1.3 Determination of Ar from mass spectra
从质谱仪中测 Ar
(1) Abundance and peaks
*analyse mass spectra in terms of isotopic abundances and molecular fragments [knowledge
of the working of the mass spectrometer is not required]
(2)principles of mass spectrometer (了解)
A: Atoms are first converted into singly charged, positive ions, when high-energy electron
collides with an atom of a vaporised sample of the element, a positive ion is formed.
B:A beam of these positive ions is accelerated by using a positively charged electrode to repel
it.
C:The beam of positive ions passes through a magnetic field where ions are deflected
according to their masses.
D:the lighter ions defleet more
E.A detector measures the relative abundance of each isotope present.
1.4 Counting chemical substances in bulk
----The mole and Avogadro’s constant
(1)definition: one mole of a substance is the amount of that substance which has the same number
of specific particles as there are atoms in exactly 12g of the carbon-12 isotope.
≈6×1023
1 million→106 个
1 万→104 个
1 mol→6×1023 个
molar mass : We often refer to the mass of a mole of substance as its molar mass (abbreviation M). The
units of molar mass are g.mol-1.
(2) 常见基本公式及基本计算
n=
m
M
n 物质的量 amount of substance （mole）
m:物质的实际质量 (g)
M:摩尔质量 molar mass (g.mol-1)
n=
N
L
(N:粒子个数
L: Avogadro’s constant 6×1023)（适合于固、液、气态）
Volume of 1 mol gas ≈ 24dm3
n=
V
V
=
(室温，室压下，只适合于气体)
Vmolar
24dm 3 mol 1
Gas Volume (气体体积): V(dm3), at room temperature, and pressure
(3) Concentration of solution (溶液浓度)
C(mol.dm-3) =
n
(n 的单位为 mol
v
v 的单位为 dm-3)
mol.dm-3 → M
3mol.dm-3 → 3M
(4) Chemical equations 化学方程式含义
C(s) + O2(g) = CO2(g)
ratio of amount of substance 1 : 1 : 1
mass of reactant 12 : 32 : 44
2H2(g) + O2(g) = 2H2O(l)
物质量比 2 : 1 : 2 (2×2
1×32
18×2)
质量比
4 : 32 : 36
1.5 Writing chemical formula (书写化学式)
(1)常见的元素及其化合价 → oxidation state
H+, Li+
Na+
K+
Mg2+, Ca2+ → Group II
Al3+
F-1
Cl- Br-1
I-, NO3-
O2-, S2-, CO32-, SO42-, SO32-
PO43(2) 书写 writing → 物质内所有元素和为零
+5
-2
P2
O5
命名规则：
① metals do not usually change their names,(金属通常在化合物中不变名称)
② non-metals change their name by becoming–ide(非金属通常在后面加-ide 后缀)
③ 非金属与非金属的化合物 eg CO2, NO2, SO3, SO2
④ 底标数字 1-mono 2-di 3-tri 4-tetra 5-penta 6-hexa 7-hepta 8-octa
(3) 命名总结：
①：金属+非金属(离子化合物)，非金属+非金属(其他化合物)
Xm 化合物为正的元素名称不变 Yn 化合物为负的后缀-ide
eg CO2 → Carbon dioxide
NaCl → Sodium chloride
②：Acid 酸 (xx acid , -ic 后缀) ③:盐 salt ④:base
(4) 名称类型
① chemical formula eg CO2, NaCl, H2SO4
② molecular formula → 分子式(以分子形式存在的物质名称)
③ empirical formulae → 最简式
分子式
最简式
N 2O 4
NO2
C3H6O2
C3H602
C4H8O2
C4H2O
H2O
H2O
C 6H 6
CH
C4H10
C2H5
总结 1 常见的数学底标
1--4--7--2--5--8--3--6--总结 2 常见的阴离子(非金属阴离子 ide 后缀)
O2- → oxide
盐→-ate
2S → sulphide
SO42- → sulphate
F- → fluoride
NO3- → Nitrate
Br - → bromide
PO4- → phosphate
C1- → chloride
SO32- → sulphite
I- → iodide
CO32- → hydrogencarbonate
3P → phosphide
HCO3- → Carbonate
eg. FeO Fe3O4 Fe2O3
FeO: iron(II)oxide Fe2O3: iron (III)oxide Fe3O4:tri-inn tetra oxide
碱： OH- hydroxide
eg: NaOH sodium hydroxide
变价：Fe(OH)3 iron(III)hydroxide
Fe(OH)2
亚铁 iron(II)hydroxide
酸： acid
H2SO4 硫酸
H3PO4 磷酸
HCl
盐酸(非含氧酸)
HNO3
硝酸
H 2S
氢硫酸
或 ferrous hydroxide
sulphuric acid
phosphoric acid
hydrochloric acid
Nitric acid
hydrosulpharic acid
1.6 Writing and Balancing chemical equation
(1) writing (标准态)
solid -- (s)
liquid – (l) gas -- (g) 水溶液 solution -- (aq)
C(s) + O2(g) → CO2(g)
2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l)
(2) Balancing chemical equations (观察法)
① 观察法配平（初中学过）
② Combustion of carbonhydrogen compounds (碳氢化合物的燃烧)
y z
y
 )O2 → XCO2 +
H2O
4 2
2
8 1
C3H8O + (3+  )O2 → 3CO2 + 4H2O
2 2
CxHyOz + (x +
(3) Writing and Balacing ionic equations(书写与配平离子方程式)
2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l)
化学方程式→离子方程式① 所有溶于水电离的物质都拆成离子②消去左右的相同离子
eg. 2Na+ + 2OH- + 2H+ + SO42- → 2Na+ + SO42- + 2H2O
2OH- + 2H+ → 2H2O → 离子反应式反应了化学变化中真正参加反应的物
OH- + H+ → H2O(l)
总结：能拆的物质（强电解质）
强酸：H2SO4 HCl HNO3 HBr HI
强碱：NaOH KOH Ca(OH)2 Ba(OH)2
可溶性盐（溶解度口诀）钾钠铵硝酸溶，硫酸去铅钡，盐酸去银汞，其他都不溶(HCO3的盐都溶)
1.7
Combustion analysis
氧化燃烧的分析法
一般适合于含 C H O 等有机物
eg: 0.500g of an organic compound X (含 C H O ) produces 0.733g of CO2 and 0.300g of H2O
on complete combustion, 又知 Mr is 60.
1. CxHyOz + O2 → X CO2 +
1
0.500
60
n=
m
M
X
0.733
44
0.500
1
60
=
0
.
733
x
44
0.500
1
60
=
y
0.300
2
18
y
H2O
2
y
2
0.300
18
x=2
y=4
Chapter 2
Atomic Structure
Content
The nucleus of the atom:
neutrons and protons,
isotopes,
proton and nucleon numbers
Learning outcomes
Candidates should be able to:
(a) *identify and describe protons, neutrons and electrons in terms of their relative charges and
relative masses
(b) *deduce the behaviour of beams of protons, neutrons and electrons in electric fields
(c) describe the distribution of mass and charges within an atom
(d) deduce the numbers of protons, neutrons and electrons present in both atoms and ions given
proton and nucleon numbers (and charge)
(e) (i) describe the contribution of protons and neutrons to atomic nuclei in terms of proton
number and nucleon number
(ii) distinguish between isotopes on the basis of different numbers
of neutrons present
1、The Structure of an atom 原子的结构
Every atom has nearly all of its mass concentrated in a tiny region in the centre of the atom called
the nucleus. The nucleus is made up of particles called nucleons. There are two types of
nucleon: protons and neutrons. Atoms of different elements have different numbers of
protons.Outside the nucleus, particles called electrons move around in regions of space called
orbitals.
Chemists often find it convenient to use a model of the atom in which electrons move around the
nucleus in electron shells. Each shell is a certain distance from the nucleus at its own particular
energy level.
In a neutral atom, the number of electrons is equal to the number of protons. A simple model of a
carbon atom is shown in Figure 2.3. This model is not very accurate but it is useful for
understanding what happens to the electrons during chemical reactions.
Figure 2.3 A model of a carbon atom.
2、 Masses and charges of electrons, protons and neutrons
质子\中子\电子的相对电荷与质量
carries a charge of +1.6×10-19C
proton
relative mass is 1
without charge, carries(has) no charge
neutron
relative mass is 1
carries a charge of -1.6×10-19C
electron
mass of the electron is 1/1836 of that of neutron/proton ,negligible.
Summary:
Sub-atomic
particle
electron
Symbol
Relative
e
1/1836
neutron
n
1
0
proton
p
1
+1
Table 2.2 Comparing electrons, neutrons and protons.
mass
Relative
charge
－1
3、 behavior of protons，electrons and neutrons in electric field.
When a beam of electrons, neutrons and protons with the same speed,are incident
into an electric field, we will observe such behavior:
1.direction of the deviation: electrons deviate to the positive pole, protons deviate to
the negative pole,and neutrons do not deviate，because electrons carry negative charge,
neutrons no charge,and protons positive charge.
2.extent of the deviation: electrons deviate more than protons because its mass is far
smaller(1/1836) than that of proton.
4、deduce number of protons neutrons, electrons of an atom or ion in term of
atomic number and mass number.
Almost the total mass of an atom rests on the nucleus, because mass of electrons
is very small relative to that of proton and neutron .In an atom,there are same number
of protons and electrons, and proton and electron carry the same amount of but
opposite charge,so the atom is neutral.For an atom：
number of electron = number of proton = Atomic number
Nucleon number(mass number) = proton number + neutron number
B
A
X
( B:nucleon number, A:proton number/atomic number)
neutron number = B – A
eg、
19
9
F
23
11
Na 
32
16
S 2
NO3
5、 isotopes 同位素
Definition：Atoms which have the same number of protons but different number of neutrons.
Because electrons hold the key to almost the whole of chemistry, so isotopes have the same
chemistry（chemical properties）. 因为电子几乎决定了原子的所有化学性质，所以同位素的
化学性质相同。
Chapter 3 Electrons in Atoms
Content
Electrons:
electronic energy levels,
ionisation energies,
atomic orbitals,
extranuclear structure
Learning outcomes
Candidates should be able to:
(f) *describe the number and relative energies of the s, p and d orbitals for the principal quantum
numbers 1, 2 and 3 and also the 4s and 4p orbitals.
(g) *describe the shapes of s and p orbitals
(h) state the electronic configuration of atoms and ions given the proton number (and charge)
(i) (i) explain and use the term ionisation energy
(ii) explain the factors influencing the ionisation energies of elements
(iii) *explain the trends in ionisation energies across a Period and
down a Group of the Periodic Table (see also Section 9)
(j) deduce the electronic configurations of elements from successive
ionisation energy data
(k) *interpret successive ionisation energy data of an element in terms
of the position of that element within the Periodic Table
3.1 Simple electronic structure
The arrangement of electrons in an atom is called its electronic structure or electronic
configuration.
Some electronic configurations are shown in Figure 3.2
Figure 3.2 The simple electronic structures of lithium, neon and chlorine. The nudei of the atoms are not shown.
3.2Evidence for electronic structure : ionisation energy
ionisation energy 电离能
(1) Definition：the first ionisation energy of an element is the amount of energy needed to
remove one electron from each atom in a mole of atoms of an element in the
gaseous state to form one mole of gaseus 1+ ions.
(2) Symbol Hi1 Hi2 Hi3。。。。。。。。。。。。
（3） Equation of ionisation energy:
eg. For Ca:
Hi1
Hi2
Hi3
(4) factors affecting ionisation energy(影响电离能的因素)
因素(i): The size of the nuclear charge 核电荷的大小
As the positive nuclear charge increases. the attractive force between the nucleus and the
electrons increases. So, more energy is needed to overcome these attractive forces to removed the
electron.The nuclear charge increases, ionisation energy increase
因素(ii): Distance of outer electrons from the nucleus
As the distance between them increases, the attraction between the electrons and nucleus
decreases,so the ionisation energy decreases too.
因素(iii): Shielding effect of inner electrons
About Shielding effect : Since all electrons are negatively charged, they repel each other.
Electrons in inner shells repel electrons in outer shells. Full inner shells of electrons prevent
the full nuclear charge being felt by the outer electrons. This is called shielding.
★Since electrons are all negatively charged,Electrons in inner shells repel electrons in outer
shells, as the number of electrons in inner shells increases, the shielding increases ,the
ionisation energy decreases.
Hits: 比较不同的粒子(原子，离子)半径的方法:
先看电子层(shells)数目，电层数↑半径↑，当电子层相同，看质子数，质子数↑半径↓。
(5) Successive ionisation energy 连续电离能
We can continue to remove electrons from an atom until only the nucleus is left. We call this
sequence of ionisation energies, successive ionisation energies. The data in Table 3.2 shows us that:
1 H 1310
2 He 2370
5250
3 Li 519
7300
11800
4 Be 900
1760
14850
21000
5 B 799
2420
3660
25000
32800
6220
37800
47300
1
6 C 1090
2350
4620
7 N 1400
2860
4580
7480
9450
53300
64400
8 0 1310
3390
5320
7450
11000
13300
71300
84100
9 F 1680
3370
6040
8410
11000
15200
17900
92000
106000
10 Ne 2080
3950
6150
9290
12200
15200
20000
23000
117000 131400
11 Na 494
4560
6940
9540
13400
16600
20100
25500
28900
141000 158700
Table 3.2 Successive ionisation energies for the first 11 elements in the Periodic Table.
features 特征:
(a)For each element, the successive ionisation energies increase when removing electrons from the
same shell.
.This is because the charge on the ion gets greater as each electron is removed. As each electron is
removed there is a greater attractive force between the positively charged protons in the nucleus
and the remaining negatively charged electrons. Therefore more energy is needed to overcome
these attractive forces.
(b)There is a big difference between some successive ionisation energies.
For nitrogen this occurs between the 5th and 6th ionisation energies. For sodium the first big
difference occurs between the 1st and 2nd ionisation energies. These large changes indicate that for
the second of these two ionisation energies the electron being removed is from a principal quantum
shell closer to the nucleus.
(5) Application for successive ionisation energy
Interpreting successive ionisation energies
Take Al for example:The sketch graph shows the 13 successive ionisation energies of aluminium.
Number of electrons removed
3.3 Sub-shells and atomic orbitals
(1) Quantum sub-shells
n=1 n=2 n=3
The principal quantum shells, apart from the first, are split into sub-shells (sub-levels). Each
principal quantum shell contains a different number of sub-shells. The subshells are distinguished
by the letters s, p or d. There are also f sub-shells for elements with more than 57 electrons. Figure
3.6 shows the sub-shells for the first four principal quantum levels. In any principal quantum shell,
the energy of the electrons in the sub-shells increases in the order s﹤p﹤d
The maximum number of electrons that are allowed in each sub-shell is: s - 2 electrons, p - 6
electrons, d - 10 electrons.
Summary : types of sub-shells:
n=1，s;
n=2，s,p;
n=3，s, p, d;
n=4，s, p, d, f;
(2) Atomic orbitals
Each sub-shell contains one or more atomic orbitals . each orbital can only hold a maximum of two
electrons.
(3) Shapes of the orbitals
Each orbital has a three-dimensional shape. Within this shape there is a high probability of finding
the electron or electrons in the orbital. Figure 3.7 shows how we represent their shapes.
(i) s orbitals:
1s
(ii) p orbitals
be aware: 2s orbital is larger than 1s,but the same shape
(4) Filling the shells and orbitals
The most stable electronic configuration (electronic structure) of an atom is the one that has the
lowest amount of energy. The order in which the sub-shells are filled depends on their relative
energy, the order of energy levels of the sub-shells are shown below, in increasing order:
1s 2s 2p 3s 3p 4s 3d 4p 4d 4f
(5) pauli exclusion principle and spin-paired
同一轨道电子必须 opposite spin,最稳定的 electron configuration 是两种:
全充满(反旋)
半充满
3.4 A more complex model for electronic configurations
Representing electronic configurations
Element Symbol
number
Electronic configuration
1
H
Is1
2
He
Is2
3
Li
Is2 2s1
4
Be
Is2 2s2
5
B
ls22s2 2p’
6
C
ls22s22p2
7
N
ls22s22p3
8
0
ls22s22p4
9
F
ls22s22p5
10
Ne
ls22s22p6
11
Na
ls22s22p63s!
Table 3.5 Electronic configurations for the first 18 elements in the Periodic Table.
Element Name (Symbol)
number
Electronic
configuration
19
Potassium (K)
[Ar] 4s1
20
Calcium (Ca)
[Ar] 4s2
21
Scandium (Sc)
[Ar] 3d14s2
24
Chromium (Cr)
[Ar]3d54s’
25
Manganese (Mn)
[Ar]3d54s2
29
Copper (Cu)
[Ar] 3d104s'
30
Zinc (Zn)
[Ar]3d104s2
31
Gallium (Ga)
[Ar]3d,04s24p1
35
Bromine (Br)
[Ar]3d'°4s24p5
36
Krypton (Kr)
[Ar]3d104s24p6
Table 3.6 Electronic configurations for some of the elements 19 to 36, where
[Ar] is the electronic structure of argon ls 22's22p63s23p6.
★Chromium and copper
The electronic configurations of chromium and copper do not follow the expected pattern.
Chromium has the electronic configuration [Ar] 3d5 4s1 (rather than the expected [Ar] 3d4 4s2).
Copper has the electronic configuration [Ar] 3d10 4s1 (rather than the expected [Ar] 3d9 4s2).
Orbitals and the Periodic Table
The arrangement of elements in the Periodic Table reflect the electronic structure of the elements. The
Periodic Table can be split into blocks of elements (Figure 3.10).
• Elements in Groups I and II have outer electrons in an s sub-shell.
• Elements in Groups III to 0 (apart from He) have outer electrons in a p sub-shell.
• Elements that add electrons to the d sub-shells are called the d-block elements. Most of these are
transition elements.
Filling the orbitals
A usefi.il way of representing electronic configurations is a diagram which places electrons in boxes
(Figure 3.11).
• Each box represents an atomic orbital.
• The boxes (orbitals) can be arranged in order of increasing energy from bottom to top.
• An electron is represented by an arrow.
The direction of the arrow represents the ‘spin of the electron. (We imagine an electron rotating around
its own axis either in a clockwise or anticlockwise
Electronic configuration of ions
: easy !!
3.2Patterns in ionisation energies in the Periodic Table
(1)
Patterns across a period
Figure 3.13 shows how the first ionisation energy, A changes across the first two periods. We can
explain the form of the graph mainly by referring to the three things that influence ionisation energies
1) There is a general increase in &Hn across a period. This applies to Period 1 (hydrogen and
helium),Period 2 (lithium to neon) and also to other periods. As you go across a period the
nuclear charge increases. But the electron removed comes from the same shell. So,the force of
attraction between the positive nucleus and the outer negative electrons increases across the
period because:
i the nuclear charge increases
ii the distance between the nucleus and the outer electron remains reasonably constant
iii the shielding by inner shells remains reasonably constant.
2)There is a rapid decrease in ionisation energy between the last element in one period and the first
element in the next period.
i the distance between the nucleus and the outer electron increases
ii the shielding by inner shells increases
iii these two factors outweigh the increased nuclear charge.
3) Although boron has one more proton than beryllium, there is a slight decrease in Hi1 on removal
of the outer election. Beryllium has the electronic structure Is22s2 and boron has the electronic
structure1s2 2s22p1 . The electron removed in boron is in the 2p sub-shell, which is slightly further
away from the nucleus than the 2s sub-shell. There is less attraction between the electron in boron
and the nucleus because:
i the distance between the nucleus and the outer electron increases slightly
ii the shielding by inner shells increases slightly
iii these two factors outweigh the increased nuclear charge.
4)There is a slight decrease in Hi1nbetween nitrogen and oxygen. Oxygen has one more proton than
nitrogen and the electron removed is in the same 2p subshell. However, the spin-pairing of the
electrons plays a part here. If you look back at Figure 3.12, you will see that the electron removed
from the nitrogen is from an orbital which contains an unpaired electron. The electron removed
from the oxygen is from the orbital which contains a pair of
electrons. The extra repulsion between the pair of electrons in this orbital results in less energy
being needed to remove an electron. So Hi1 for oxygen is lower, because of spin-pair repulsion.
Note :These patterns repeat themselves across the third period.
Patterns down a group
The first ionisation energy decreases as you go down a group in
the
Periodic Table. For example, in Group I the values of Hi1 are:
• Li = 519 kj mol'1
• Na = 494 kj mol'1
• K = 418 kj mol"1
• Rb = 403 kj mol-1
As you go down the group, the outer electron removed is from a successively higher principal
quantum level - 2s from lithium, 3s for sodium and 4s for potassium.
Although the nuclear charge is increasing down the group there is less ,
attraction between the outer electron and the nucleus because
i the distance between the nucleus and the outer electron increases
ii the shielding by complete inner shells increases
iii these two factors outweigh the increased nuclear charge.
Chapter 4
Chemical bonding and structure
Content
I Ionic (electrovalent) bonding
II Covalent bonding and coordinate (dative covalent) bonding
(i) The shapes of simple molecules (ii) Bond energies, bond lengths and bond polarities
III Intermolecular forces, including hydrogen bonding
IV Metallic bonding
V Bonding and physical properties
Learning outcomes
Candidates should be able to:
(a) *describe ionic (electrovalent) bonding, as in sodium chloride and
magnesium oxide, including the use of ‘dot-and-cross’ diagrams
(b) *describe, including the use of ‘dot-and-cross’ diagrams,
(i) covalent bonding, as in hydrogen, oxygen, chlorine, hydrogen
chloride, carbon dioxide, methane, ethene
(ii) co-ordinate (dative covalent) bonding, as in the formation of the
ammonium ion and in the Al2Cl6 molecule
(c) *explain the shapes of, and bond angles in, molecules by using the qualitative model of
electron-pair repulsion (including lone pairs), using as simple examples: BF3 (trigonal), CO2
(linear),CH4 (tetrahedral), NH3 (pyramidal), H2O (non-linear), SF6 (octahedral)
(d) *describe covalent bonding in terms of orbital overlap, giving σ and π bonds
(e) *explain the shape of, and bond angles in, the ethane, ethene and benzene molecules in terms
of σ and π bonds (see also Section 10.1)
(f) predict the shapes of, and bond angles in, molecules analogous to those specified in (c) and (e)
(g) describe hydrogen bonding, using ammonia and water as simple examples of molecules
containing N-H and O-H groups
(h) explain the terms bond energy, bond length and bond polarity and use
them to compare the reactivities of covalent bonds (see also 5b(ii))
(i) *describe intermolecular forces (van der Waals’ forces), based onpermanent and induced
dipoles, as in CHCl3(l); Br2(l) and the liquid noble gases
(j) describe metallic bonding in terms of a lattice of positive ions surrounded by mobile electrons
(k) *describe, interpret and/or predict the effect of different types of bonding (ionic bonding,
covalent bonding, hydrogen bonding, other intermolecular interactions, metallic bonding) on
the physical properties of substances
(l) deduce the type of bonding present from given information
(m) show understanding of chemical reactions in terms of energy
transfers associated with the breaking and making of chemical bonds
4.1 ionic bonding and ionic compound 离子键与离子化合物
(1)definition 实质是什么？
Ionic bonding results from the electrostatic attraction between the oppositely charged ions.离子
键是电性相反的离子间的静电吸引。
注：离子键一般都是金属离子（或 NH4+）与非金属离子形成的。
(3) formation of ionic bonging 形成过程
稳定结构：the electronic structure of Noble gas 即最外层 8 电子结构或 He 原子结构
eg :NaCl
Figure 4.2 The formation of a sodium ion and chloride ion by electron transfer.
(3)dot-and-cross diagrams of formation of ionic bonding (用点叉图表示离子键形成过程)
（4）describe the lattice structure of sodium chloride and Magnesium Oxide
Sodium chloride has a cubic ionic lattice, Magnesium oxide has the same cubic structure with
magnesium ions in place of sodium ions and oxide ions in place of chloride ions .
Diagram of lattice cell of sodium chloride :
（6）properties of ionic compounds 离子化合物典型性质
@-@ Ionic compounds are solids with high melting points, high boiling points and high enthalpy
changes of vaporisation. This is because: there are strong electrostatic forces (ionic bonds) holding
the positive and negative ions together, It takes a lot of energy to overcome the strong electrostatic
attractive forces.
Note: Factors affecting the b.p and m.p of ionic compounds: The melting point usually increases
as the charges on the ions increase. eg,Sodium chloride with its singly charged ions has a melting
point of 1074k, and magnesium oxide with its doubly charged ions has a melting point of 3125k.
@-@ conduct electricity, with decomposition at the electrodes, in aqueous solution or when they
are molten;在水溶液中有电极的条件下或熔融状态下，分解，导电。
@-@ are hard and brittle with crystals that cleave easily;是坚而脆的晶体，易切割。
@-@ are often soluble in water 一般溶于水。
（7）electrolysis 离子化合物电解的原理
When in aqueous solution or when they are molten, ions are free to more through the aqueous
solution and molten compound and are attracted to the opposite charged electrode. At the
electrode, the ions discharge. this process is called electrolysis.
Electrolysis of ionic compounds can only occur when the ions are free to move. In the lattice
the ions are in fixed positions, and ionic solids will thus not conduct electricity. On melting, or
dissolving so they are free to move towards electrodes.只有当离子化合物中的离子可以自由
移动时，才能电解离子化合物。在晶格中，离子的位置是固定的，离子固体不能导电。当
离子化合物熔化时，或者溶解在水中时，离子的位置不再固定，所以它们可以自由移动，
移向电极放电。
4.2 Covalent bond and compounds of covalent bond
共价键与共价化合物
(1)definition 实质是什么? shared pair of electrons between two atoms.
@-@ In covalent compounds, electrons are shared in pairs. The negative charge of the
electron-pair will attract the positively charged nuclei of the elements, and this holds the atoms
together in a molecule. The electron-pair must lie between the nuclei for the attraction to outweigh
the repulsion between the nuclei. 在共价化合物中，两个原子共用一对电子。电子对中带负电
的部分吸引带正电的元素的原子核。这样使原子聚集在一个分子中。由于两个核子之间的引
力大于斥力，所以电子对必须位于两个核子之间。
@-@ Under such circumstances two atoms will be bound together by a covalent bond. In a
molecule, atoms will share electrons, and, as a general rule, the number shared gives each atom
filled outer shells similar to the electronic configuration of a noble gas.在这种情况下，两个原子
靠共价键结合在一起。在分子中，原子共用电子，并且一般情况下共用的电子数是使得各个
原子的外壳电子层结构与稀有气体的电子层结构相似。
@-@ Each covalent bond is a shared pair of electrons.
@-@ Covalent bonds are usually formed between pairs of non-metallic elements.一般是非金属
元素间形成共价键。(注：共价键一般都是非金属与非金属原子间形成的)
(2)dot-and-cross diagram formation 点叉图与形成过程
+
→
→
(3)dative covalent bond/coordinate bond
(ⅰ)Lone-pairs 孤对电子:Atoms in molecules frequently have pairs of electrons in their outer
shells that are not involved in covalent bonds. These non-bonding electron-pairs are called
lone-pairs.分子中的原子的外层电子经常没有参与形成共价键形成电子对。这些没有成键的
电子对被称为孤对电子。In ammonia, nitrogen has one lone-pair, and in water, oxygen has two
lone-pairs.
(ⅱ) Sometimes these lone-pairs are used to form a covalent bond to an atom that can
accommodate two further electrons in its outer shell. An example is when ammonia and the
hydrogen ion combine to form the ammonium ion,NH4+(shown below)有时这些孤对电子可以与
能容纳另外两个电子的原子形成共价键。例如，氨与一个氢离子结合成为铵离子，NH4+（如
下所示）
：
NH3
NH 
 
4
+
H+
→
@-@ Dative covalent bonds are represented by arrows in displayed formulae of molecules. Dative
covalent bonds are also called coordinate bonds in metal complexes.
H
H
N
H
H
A further example of coordinate bonding is found in aluminium chloride. When solid aluminium
chloride is heated, it becomes a vapour at 180℃. The vapour consists of Al2Cl6 molecules, which
have the following structure 在氯化铝中也存在配位键，当加热固体氯化铝到 180℃时，就变为
蒸气，在蒸气中含有 Al3Cl6 分子，Al3Cl6 含有如下的结构:
Cl
Cl
Cl
Al
Al
Cl
Cl
Cl
Two chlorine atoms each donate a lone-pair of electrons to a vacant orbital of an aluminium
atom.其中的两个氯原子每个提供一对孤对电子给铝原子的空轨道。
Figure 5.15 The structure of silicon(IV) oxide.
4.2 Metallic bonding and giant metallic structure
(16)Summary of bonding and structures
所有纯净物结构的分类(晶体类型)
Giant
metallic
lattice
structure
金属键
metallic
Giant
ionic
lattice
structure
离子键形成的
ionic bond
Simple
molecular
lattice
structure
Giant
covalent(or
molecular)lattice
structure
共价键形成
covalent bond
（4）  and  bond
@-@ In molecules, atomic orbitals combine to produce
 and  molecular orbitals.
在分子中，原子轨道结合成 σ，π 分子轨道。
In a molecule the bonding electrons are now in molecular orbitals rather than
atomic orbitals. The molecular orbitals may be considered to arise from the overlap of
atomic orbitals.
Molecular orbitals are given labels using Greek letters:  ,  ,  , etc.(pronounced
sigma, pi, delta, respectively).These parallel the labels for atomic orbitals: s, p, d, etc.
A single covalent bond consists of a  orbital and is often called a  bond.
A double covalent bond consists of a  bond and a  bond.
在分子中，成键电子是在分子轨道上，而不是在原子轨道上，可以看作是原子轨道的重
叠。我们用希腊字母 σ，π，δ 等来表示分子轨道。共价单键只包括 σ 轨道，通常称作 σ 键。
氢分子中是 σ 键。π 键中存在 π 轨道。共价双键由一个 σ 轨道和一个 π 轨道组成。
The graph below shows the  bond  bonds:
(5) Polar molecules and non-polar molecules
（ⅰ）Electronegativity is the ability of a bonded atom to attract electron charge.
电负性是指成键原子吸引电荷的能力。
电负性变化的规律:The electronegativity of the elements increases from Group to Group
VII across the Periodic Table. Electronegativity also increases up a Group of elements as the
proton number decreases.在周期表中，从第Ⅰ族到第Ⅶ族，元素的电负性逐渐增加。在同一族
中，随着元素质子数的递减，电负性增大。
For our purposes, it is sufficient to recognize that electronegativities increase
＠－＠ from left to right across a Period in the Periodic Table
＠－＠ vertically up Groups.
因此，我们规定，在周期表中，同一横行从左到右，同一纵行从下到上，元素的电负
性逐渐增大。
Eg. increasing electronegativity 电负性递增的顺序
C1 ＜ N ＜ O ＜ F
电负性关系：eg O Cl F N
↓ ↓ ↓ ↓
8
3 9 7
半径 Cl ＞ N ＞ O ＞ F
electronegativity Cl ＜ N ＜ O ＜ F
电负性 F ＞ Cl ＞ Br ＞ I
(ⅱ) Polar Covalent bonds and non-polar covalent bonds
Covalent bonds in molecules are polar if there is difference in electronegativity between the
elements.
如果成键的元素的原子电负性不同，形成的共价键就是有 polar covalent 极性共价键。
如果成键的元素的原子电负性相同，形成的共价键就是 non-polar covalent 非极性共价键。
极性共价键由两不同原子形成，例如 Cl-Cl,0=0,非极性共价键由两个相同原子形成键，
例如 H-Cl.
（ⅲ）Polar molecules and non-polar molecules 极性分子和非极性分子
判断分子是否为极性或非极性的方法：
(a) diatomic molecules which consist of two same atom are always nonpolar eg:Cl2, H2, N2 两
个原子相同，就是非极性分子，两个原子不同，就是极性分子。eg：
O2 — nonpolar
HF -- polar
(b)polyatomic molecules 多原子分子
一般直线形，正面体，平面三角形，直线型，八面体等对称的分子形状是非极性。
对于多原子，极性与非极性是由形状决定的，只有知道分子实际形状，才能知道其极
性或非极性。
常见 eg：
SAQ :
CH3Br -- polar
H2O—polar
（c）how to predict qualitively the magnitude of the overall dipole of a molecule
(7) electron-pair repulsion theory 电子对互斥理论
lone pair(LP) Bonding pair(BP) and bond angle
electrons are negatively charged, they exert a repulsion on each other. Each pair will repel
each of the other pairs. The effect of these repulsions will cause the electron-pairs to move as far
apart as possible.
因为电子带负电互相排斥，它们彼此施加斥力。每对电子彼此的排斥使它们尽可能的远离。
顺序：Lp-Lp, repulsion ＞ Lp-Bp repulsion ＞ Bp-Bp repulsion 解释键角问题
eg: CH4 中
NH3 中
H20 中
(8) shapes of simple molecules 分子晶体 研究对象时分子
(a)The prediction of shapes of simple molecule 简单分子形状的预测
In order to predict the shape of a molecule, the number of pairs of outer-shell electrons on the
central atom is needed. It is best to start with a dot-and-cross diagram and then to count the
electron-pairs, as shown in the following examples.在预测分子的形状时，我们需要知道中心原子的外
壳的孤对电子数。我们最好用点叉图表示电子对的数目。下面是几个例子。
(i)centural atom four bonding electron pairs(中心电子有 4 对成键电子)→tetrahedron(四面
体)→典型的代表物 CH4 :C 位于四面体中心，H 位于 4 个顶点上。
(ii) The centural atom has three bonding electron pairs(中心原子有 3 对成键电子
对)→triangular pyramidal molecules(三角锥结构)
典型代表物：NH3
(iii)The centural atom has two bonding electron pairs( 中 心原 子有 2 个成键电 子
对)→non-linear or bent molecule
典型代表物水 H2O
(iv) linear molecular (直线性分子)
典型代表物 CO2
(v) The centural atom only has three pairs of electron, which are bonding 中心原子只有 3
对电子，且都成)→trigonal planar molecule(平面三角形)
典型代表物 BF3
This is an interesting molecule, at only has six electrons in the bonding shell on boron,
distributed between three bonding pairs. The three bonding pairs repel each other equally, forming
a trigonal planar molecule with bond angles of 120°. Boron trifluoride is very reactive and will
accept a non-bonding(lone) pair of electrons. For example, with ammonia H3N→BF3 is formed
(note the dative covalent bond indicated by the arrow).
三氟化硼的分子很奇特，在硼原子的成键电子层上含有六个电子，形成三对成键电子。
三对电子间的排斥力相同，形成键角是 120°的三角形分子。三氟化硼的活性很高，可以接
受非成键电子对。例如：可以和氨反应，H3N→BF3（配位键用弓形表示）。
(vi)中心原子仅有 6 对电子，都成键→sulphur hexafluoride 典型代表物 SF6
There are six bonding pairs and no lone-pairs. Repulsion between six electron-pairs produces the
structure shown. All angles are 90°. The shape produced is an octahedron (i.e. eight faces).在六氟
化硫中含有六对成键电子对，没有孤对电子。六对电子之间的排斥力导致分子的形状如下
所示。所有的键角都是 90°，分子的形状是八面体。
(b) bond angles 孤对电子，成键电子对和键角
Lone-pairs of electrons are attracted by only one nucleus, unlike bonding pairs, which are
shared between two nuclei. As a result, lone-pairs occupy a molecular orbital that is pulled closer
to the nucleus than bonding pairs. The electron charge-cloud in a lone-pair has a greater width
than a bonding pair.成键电子对是两个核子共用，而孤对电子是只被一个核子吸引。孤对电子
比成键电子对离核子更近，占据分子轨道，孤对电子的电子云密度比成键电子的要大。
The diagram below shows the repulsions between lone-pairs(pink) and bonding pairs (white)
in a water molecule.下图表示的水分子中孤对电子与成键电子间的排斥作用。
孤对电子间的排斥力最大
瞬时排斥力
O
H
H
H-O-H键角是104.5°
成键电子的排斥力最小
The repulsion between lone-pairs is thus greater than that between a lone-pair and a bonding
pair. The repulsion between a lone-pair(LP) and a bonding pair(BP) is greater than that between
two bonding pairs.To summarise：
＠－＠ LP-LP repulsion ＞ LP-BP repulsion ＞ BP-BP repulsion
孤对电子间的排斥作用显然要比孤对电子与成键电子对间的排斥作用要大。孤对电子
（LP）与成键电子对（BP）的排斥作用要大于成键电子对间的排斥作用。总结如下：
LP-LP 间的排斥作用>LP-BP 间的排斥作用>BP-BP 间的排斥作用
This variation in repulsion produces small but measurable effects on the bond angles in
molecules. In methane, all the HCH angles are the same at 109.5°. In ammonia, the slightly
greater repulsion of the lone-pair pushes the bonding pairs slightly closer together and the angle
reduces to 107°. In water, two lone-pairs reduce the HOH angle to 104.5°.
这种排斥力的变化对于分子形状的影响虽然很小，但是可以影响分子的键角。在甲烷
中，所有的 HCH 键角都是 109.5°，在氨中，由于孤对电子的排斥力稍微大一些，所以使得
成键电子对相互靠近，键角变为 107°。在水中，两对对孤对电子的影响，使得 HOH 的键角
变为 104.5°。
(9) Bond enthalpy and bond length (键焓能与键长)
Definition :The bond enthalpy is the energy required to break one mole of the given bond in the
gaseous molecule.
In general, double bonds are shorter than single bonds. In addition, the energy required to break a
double bond is greater than that needed to break a single bond. The bond enthalpy is the energy
required to break one mole of the given bond in the gaseous molecule(see also chapter 5, page76).
Table 3.2 shows some examples of bond enthalpies and bond lengths.
一般情况下，双键比
单键要短，并且断裂双键所需的键能要大于断裂单键所需的键能。键焓就是打开气态分子的
一摩尔的化学键所需的能量.
(10) Intermolecular force → 分子间力主要用来解释简单小分子结构的物质的熔沸点
常见分子间作用力的类型及产生原因
① Instantaneous dipole-induced dipole forces (temporary dipole forces)
(i)成因：At any instant it is possible for more electrons to lie to one side of the atom or
molecule than the other, and an instantaneous electric dipole occurs.(在任何一
时刻，电子可能在原子或分子的一端多，而另一端少，于是瞬时电偶形成。)
This instantaneous dipole produces an induced dipole in a neighbouring atom or
molecule, which hence attracted.(这种瞬时的电偶使它相邻的分子或原 子产
生诱导电偶，于是两者互相吸引。)
Intermolecular force of this type is called instantaneous dipole-induced dipole
forces 这种分子间力称为瞬时诱导力。
(ii)影响因素：number of electrons and protons of atoms in the molecule increase,
instantaneous dipole-induced dipole forces increases.
②permanent dipole-dipole forces
永久电偶力→极性分子→共价键的化合物
③Hydrogen bond 氢键→发生在含 O,F,N 的氢化物.(O,F,N 电负性极高)
一般时，一但化合物突然出现某一个的熔沸点突变，从氢键考虑。
氢化物典型的-OH ,–NH.
eg1:
eg2:
eg3:
(13)Strength of different kind of bolding：
USUALLY ,
instantaneous dipole-induced dipole forces ＜permanent dipole-dipole forces ＜hydrogen
bond ＜ covalent bond/ionic bond
(14)Application of intermolecular forces 分子间作用力应用
to explain the boiling and melting points in the substances with simple molecular
sutructure
(15)水的特殊性质
The anomalous properties of water resulting from hydrogen bonding. (冰中氢键由于氢键
引起的水的异常性质)
in ice, a three-dimensional hydrogen-bonded lattice is produced, each oxygen is surrounded
by a tetrahedron of hydrogen atoms bonded to further oxygen atom.
在冰中，一个三维的由氢键固定的晶体。每个 O 原子由氢键连接的 H 原子形成四面体
结构。
The high tension of water surface is due to hydrogen bonding of water
3 Metallic bonding and giant metallic lattice structure 金属键与巨型金属晶体
（1） formation of metallic bond
In a metallic lattice, the atoms lose their outer-shell electrons to become positive ions. The
outer-shell electrons occupy new energy levels, which extend throughout the metal lattice.
The bonding is often described as a ‘sea’ of mobile electrons surrounding a lattice of positive
ions. The lattice is held together by the strong attractive forces between the mobile electrons and
the positive ions.在金属晶格中，金属失去它的最外层电子变成正电子。分布在整个晶格的外
层电子又占有新的能量级。成键被描述为在正离子的晶格存在着自由电子。
(2) definition of metallic bond :strong attractive forces between the mobile electrons and the
positive ions.
(3)properties of metals due to its metallic bond
Metals have very different properties to both ionic and covalent compounds.
＠In appearance they are usually shiny(figure 3.15).
＠They are good conductors of both heat and electricity (the latter in the solid state and
without decomposition, unlike ionic compounds).
＠They are easily worked and may be drawn into wires or hammered into a different shape, i.
e. they are ductile and malleable.
＠They often possess high tensile strengths and they are usually hard.
金属一般有金属光泽,它们都是热和电的良导体（后者在固态不分解的情况就可以，不像
离子化合物）
。金属化合物的用途广泛，可以用作导线，还可以被做成不同的形状。也就是
说，它们有延展性和可塑性。金属一般有很强的张力，并且硬度很大.
(3)The properties of metals can be explained in terms of this model of the bonding
金属的性质可以用成键的这种模型得到解释。
Electrical conduction can take place in any direction, as electrons are free to move
throughout the lattice.由于自由电子可以在晶格内自由移动，所以金属可以导电。
Conduction of heat occurs by vibration of the positive ions as well as via the mobile electrons.
由于正电子与自由电子的振动，所以金属可以传热。
Metal are both ductile and malleable because the bonding in the metallic lattice is not broken
when they are physically deformed .As a metal is hammered or drawn into a wire, the metal ions
slide over each other to new lattice position ns. The mobile electrons continue to hold the lattice
together.金属有延展性，所以只是改变金属的物理形状，金属晶格内的键是不被破坏的。金
属被锻压成导线，金属离子之间相互移动，形成新的晶格位置。自由电子仍能使晶格紧靠在
一起。
Some metals will even flow under their own weight. Lead has a problem in this respect. It is
often used on roofs where, over the years, it suffers from ‘creep’. This is not only from thieves but
also because the metal slowly flows under the influence of gravity.
The transition elements are metals that possess both hardness and high tensile strength.
Hardness and high tensile strength are also due to the strong attractive forces between the metal
ions and the mobile electrons in the lattice.过渡元素都是金属，它们的硬度，强度很大。硬度
和强度归结为自由电子和金属离子间的强大引力。