Download The Periodic Table of Elements

The Periodic Table of Elements
Notes
The Periodic Table








Elements are arranged in order of proton numbers
Vertical columns of elements are called groups
Horizontal rows of elements are called periods
Across the period, the elements change from metals to non-metals
Elements close to the staircase line, like silicon or germanium, can have some
properties of the metals and of the non-metals --> metalloids
Group number: indicates number of electrons in the outermost shell of an atom
Period number: indicates the number of electron shells in an atom
Metals always from positive ions while non-metals always form negative
ions
Source: http://aphschem.blogspot.com/2009/09/92209-metal-or-non-metal.html
Group I and II
metals
Properties
 Group I : alkali metals
 Group II: alkaline earth metals
 reactive
 reactivity increases down the group
Metalloids- elements
close to the
staircase line


have properties of both metals and non-metals
metalloids beneath the staircase line are called
Poor Metals (eg tin and lead)
Non-metals



often gases (except Br, P, S, C, B, Se)
low melting points
poor conductors of heat and electricity (except
graphite)
form mainly covalent compounds

Transition metals








typical metals
strong and hard
good conductors of heat and electricity
high melting points
many of these metals have variable oxidation state
eg Copper(I) and Copper(II), Iron(II) and Iron(III)
not very reactive
compounds formed often have characteristic
colours. Examples:
 Copper(II) compounds are blue
 Iron(II) compounds are green
 Iron(III) compounds are yellow and green
 Manganate(VII) compounds are purple
 Dichromate compounds are orange
transition metals and their compounds are used as
catalysts to speed up industrial reactions.
Examples:
 iron in Haber Process to manufacture
ammonia
 Nickel used in manufacture of margarine
from vegetable oils
 Platinum or vanadium(V) oxide in the
Contact Process to manufacture sulphuric
acid
Periodic Law


Elements in same group has the same number of valence shell electrons which the amount
is the same as the group number.
 e.g. Group II has elements with valency of 2 electrons.
The charges relates to the group number and number of valence electrons.







Elements on left side periodic table lose ions to form cation.
Elements on right side periodic table gain ions to form anion
Elements in Group IV can lose or gain electrons depending on reacting element.
Transition metals may form variable cation of 2+ or 3+
Elements in same group form same type and number of bonds due to the same number of
valence electrons.
 e.g. Sodium in Group I forms NaCl, so other elements in Group I does the same.
(RbCl, KCl, LiCl, CsCl)
From left to right, elements gradually change from metal to non-metal
Elements close to dividing line in periodic table in back part of the note (in bold) are called
metalloids having properties of metals and non-metals.
Properties
Trend down a group
Trend across a period (Left to
Right)
the size of the atom increases the size of atom decreases
decreases down a group
increases across a period
Atomic size
Ionization
energy*
Electron affinity* decreases down a group
Electronegativity* decreases down a group
Electropositivity* increases down a group




increases across a period
increases across a period
decreases across a period
Ionization energy is the minimum amount of energy required to completely remove
an electron from a gaseous atom
The Electron affinity of a molecule or atom is the energy change when an electron
is added to the neutral atom to form a negative ion. (in simple terms, it refers to
how much an element loves an electron)
Electronegativity is the tendency for an atom to attract electrons to itself
Electropositivity is the tendency for an atom to lose an electron
Changes in Group



Proton number increase going down the group
On each sides of periodic table, the change of the proton number small & gradual
In transition metals, the gradual change is larger
Using the Periodic Table
Predicting Properties
1) Formula and Structures

Given chlorine, iodine and bromine of Group VII forms molecules of Cl2, I2 and

Br2 respectively, predict the molecular formula of Fluorine. eg. F2
From example, we know elements in same group form same formula.
2) Properties of Elements


Properties of element changes down the group.
i.e. given list of Group 7 elements, predict the properties of astatine.
Octet rule
Cations
- Metals form cations (position ions)
- Cations are smaller than their atoms
Anions
- Non-metals form anions (negative ions)
- Anions are larger than their atoms
Isotopes
- Have the same atomic number (number of protons) but different mass number or
different number of neutrons
Differences between metals and non-metals
Metals
Non-metals
Usually solids at room temperature Often gases except:
except mercury
Bromine: liquid
Sulphur: solid
Phosphorus: solid
Iodine: solid
Carbon: solid
Boron: solid
Silicon: solid
High melting and boiling points
Low melting and boiling points
(except Group I)
(except B, C, Si)
Good conductors of heat and
Poor conductors of heat and
electricity
electricity
(except carbon/graphite)
Often shiny, ductile, malleable, and Normally dull, soft, cannot be drawn
possess great tensile strength
out into wires or made into flat
sheets
Most compounds are ionic
Most compounds are covalent
Oxides are usually basic or
Oxides are usually neutral or acidic
amphoteric
Often form hydrogen gas with
Never form hydrogen gas from acids
dilute acids
Always form position ions (cations) Always form negative ions (anions)
Group I metals











called Alkali metals - the metals react with water to form alkaline solutions:
the solutions turn red litmus paper blue
have one outer shell electrons
shiny, silvery solids
soft, easily cut with scalpel
low densities and melting points - these increases down the group
good conductors of heat and electricity
reacts easily in air so they're kept in oil
chemically reactive - reactivity increases down the group (Caesium most reactive of
all metals
 This is because the atoms become larger as we go down the group.
 It becomes easier for the outermost, single valence electron to escape
to form an ion as the attractive force of the nucleus is further away
and weaker
have 1 valence electron
loses one outermost electron to form an ion of +1 charge eg. Li+, Na+, K+
react violently with air or oxygen, catching fire, and burning with characteristic


flame colors to form white oxides. To avoid this, the metals are stored under oil
 eg. 4K (s) + O2 (g) ----> 2K2O (s)
They also react vigorously with water, forming the alkaline hydroxide and
releasing hydrogen gas
 eg. 2Na (s) + 2H2O (l) ---> 2NaOH (aq) + H2 (g)
Because alkali metals are such reactive metals, they combine directly with
reactive non-metals such as the halogens to form salts
 eg. 2Na (s) + Cl2 (g) ----> 2NaCl (s)
Flame colour
Alkali metal
Li
Na
K
Rb
Flame color
red
yellow
lilac
-
Reactions of the Alkali metals
Alkali
metal
lithium
Reaction with air
(oxygen)
burns with a red
flame to give lithium
oxide (white solid)
4Li + O2 ---> 2Li2O
Reaction with water
floats on water and
reacts quickly to
produce lithium
hydroxide and
hydrogen gas
2Li + 2H2O ---> 2LiOH
+ H2
sodium
burns with a bright
floats on water and
yellow flame to
reacts very quickly to
produce white
produce sodium
sodium oxide
hydroxide and
4Na + O2 ---> 2Na2O hydrogen gas
2Na + 2H2O --->
2NaOH + H2
potassium burns violently with floats on water and
a lilac colored flame reacts violently to
to produce white
produce potassium
potassium oxide
hydroxide and
4K + O2 ---> 2K2O
hydrogen gas
2K + 2H2O ---> 2KOH +
Reaction with
chlorine
burns with a bright
flame to give a white
solid of lithium chloride
2Li + Cl2 ---> 2LiCl
burns with a bright
flame to give a white
solid of sodium
chloride
2Na + Cl2 ---> 2NaCl
burns vigorously in
chlorine with a bright
flame to give a white
solid of potassium
chloride
2K + Cl2 ---> 2KCl
H2
Group VII (Halogens)











reactive non-metals
have seven outer shell electrons
poisonous
low melting and boiling points - increases down the group
elements become darker and solidify down the group
reactivity decreases down the group
 because of their atomic size, which increases down the group
 therefore it becomes more difficult for the nucleus to attract an
electron to form an ion
most reactive is fluorine; least reactive is iodine
all halogens form ions with single negative charge eg F-, Cl-, BrExists as diatomic molecules eg F2, Cl2, Br2, I2
reacts vigorously with metals to form ionic salts
halogens become less reactive down the group
Halogen
Colour
State
Fluorine
Chlorine
Bromine
Iodine
pale yellow
yellowish green
red brown
shiny black
gas
gas
liquid
solid




Any halogen above another in the group will displace it from a solution of its salt ---> displacement reactions
This means that the more reactive halogen can take the place of the less reactive
halogen of its salt.
 eg. Cl2 + 2KBr -----> 2KCl + Br2
When chlorine gas is bubbled through a colorless solution of potassium bromide, reddish
brown color of bromine is seen.
 eg. Cl2 + 2KI ----> 2KCl + I2
When chlorine gas is bubbled through a colorless solution of potassium iodide, it turns
brown and finally a black precipitate of iodine is formed.
Group O (Noble/Inert Gases)





Exist as monatomic (single atom)
least reactive elements in the gaseous state; do not form bonds
low melting and boiling points
have stable electronic configuration with full electrons on their shells
chemically inert
 because the outermost shell of the element is full.
 It does not tend to combine with other elements, either covalently or
ionically, and there is chemically inactive
Name
Helium
Neon
Argon
Kryton
Xenon
Radon
Uses
in air ships, weather balloons
in advertising lights
an inert gas for electric bulbs,
welding and making steel
gas-filled electronic devices
and lasers
electronic flash guns
natural radioactive gas
Transition metals
Element
chromium
manganese
iron
Common ions
Cr2O72- dichromate(VI)
MnO4manganate(VII)
2+
Fe
iron(II)
3+
Fe
iron(III)
nickel
Ni2+
copper
Cu
+
nickel(II)
copper(I)
Cu2+






copper(II)
often form colored compounds
can have variable oxidation states ---> no fixed number of valence electrons
form complex ions eg MnO4- (manganate(VII) ions)
high melting and boiling points
high densities
can have catalytic properties
Industrial process
Contact Process
Description
uses vanadium(V) oxide to help in the conversion to
sulphur trioxide
Haber Process
uses an iron catalyst with iron oxide promoters to
make ammonia gas
Margarine manufacture uses nickel catalyst in the hydrogenation of alkene
Uses of transition metals
Transition metal
Tungsten
Chromium
Titanium
Manganese
Nickel
Zinc
Copper
Uses
used in filaments of electric light bulbs as it is
ductile and has a melting point over 3000oC
hard, unreactive (has protective oxide coating)
and attractive. So used for chromium-plating
and in making stainless steel
titanium and its alloys are light but as strong as
steel so used in aircraft construction
hard brittle metal used to harden steel
a strong metal that resists corrosion. Used in
stainless steel and in coinage metals like
cupronickel which has an attractive silvery
appearance
a grey metal with a blue tinge. Main use is to
galvanise iron to prevent it from rusting
unreactive metal and malleable. So used for
making water-pipes
Advantages

Since transition elements speed up chemical processes in industries, they saves time in


manufacture
Less energy is needed for manufacture in industries, hence lower cost
Since less energy is needed, more energy resources can be conserved, e.g. oil to generate
electricity in producing iron.
MCQ
1. Which property decides the order of the elements in the Periodic Table?
a. masses of their atoms
b. number of electrons in the outer shell
c. number of neutrons in the nucleus
d. number of protons in the nucleus
2. The element with a proton number 12 has similar chemical properties to the
element with the proton number
a. 2
b. 11
c. 13
d. 20
3. Which element is in Group IV, Period 5 of the Periodic Table?
a. antimony
b. arsenic
c. lead
d. tin
4. Which statement about a new element, which has seven outer electrons in its
atoms, is correct?
a. it is monatomic
b. it forms a covalent compound with hydrogen
c. it forms a positive ion
d. it forms covalent compounds with Group I elements
5. Which list contains 3 elements that all exist as diatomic molecules at room
temperature?
a. hydrogen, fluorine, neon
b. nitrogen, chlorine, neon
c nitrogen, oxygen, fluorine
d. oxygen, chlorine, helium
6. Which statement shows that iron is a transition metal?
a. Iron(II) sulphate crystals are green
b. Iron(III) oxide is basic
c. Iron rusts in moist air
d. Iron reacts with dilute hydrochloric acid
7. A metal X forms oxides with the formulae XO and X2O3
Where is X in the Periodic Table?
a. Group II
b. Group III
c. second Period
d. transition elements
8. Which of the following is a property of aqueous potassium iodide?
a. it does not conduct electricity
b. it is decolorised by chlorine
c. it reacts with aqueous bromine to form iodine
d. it reacts with aqueous lead(II) nitrate to form a white precipitate
9. Many properties of an element can its compounds can be predicted from the position of
the element in the Periodic Table. What property could not be predicted in this way?
a. acidic or basic nature of its oxide
b. formula of its oxide
c. number of isotopes it has
d. its metallic or non-metallic properties
10. The element with a proton number 12 has similar chemical properties to the element
with the proton number
a. 2
b. 11
c. 13
d. 20
11. The proton number of Indium, In, is 49. What is the most likely formula for the oxide of
Indium?
a. In2O
b. In2O3
c. InO
d. InO2
12. The element with proton number 12 has similar chemical properties to the element with
the proton number
a. 2
b. 11
c. 13
d. 20
13. Which statement about groups in the Periodic Table is correct?
a. All groups contain both metals and non-metals.
b. Atoms of elements in the same group have the same total number of electrons.
c. In Group I, reactivity decreases with increasing proton number.
d. In Group VII, the melting point of the elements increases with proton number.
14. Which property decides the order of elements in the Periodic Table?
a. masses of their atoms
b. number of electrons in the outer shell
c. number of neutrons in the nucleus
d. number of protons in the nucleus
15. An element X, necessary for plant growth, can be added to the soil only in the form of
compounds which contain the ion X. What is X?
a. hydrogen
b. nitrogen
c. phosphorus
d. potassium
16. The element Cs is in the same group of the Periodic Table as sodium and potassium.
Which of the following is likely to be a property of caesium?
a. It does not conduct electricity.
b. It reacts vigorously with water to give off hydrogen.
c. It forms the ionic chloride with formula CsCl2
d. It forms an acidic oxide.
17. Which statement is most likely to be true about the elements in Group I of the Periodic
Table?
a. They occur uncombined in nature.
b. They are equally reactive chemically.
c. They form chlorides of similr fornulae.
d. They become less metallic as the proton number increases.
18. Astatine (At) is in Group VII of the Periodic Table. Which of the following is a property
of astatine?
a. It forms a basic oxide.
b. It is a good conductor of electricity.
c. It is displaced by chlorine from aqueous potassium astatide.
d. It displaces iodine from aqueous potassium iodide.
19. Which statement about a new element, which has seven outermost electrons in its atoms,
is correct?
a. It is monatomic.
b. It forms a covalent compound with hydrogen.
c. It forms a positive ion.
d. It forms covalent compounds with Group I elements.
20. Fluorine is the first element in Group VII of the Periodic Table. Which statement will
not be true of fluorine?
a. Fluorine exists in diatomic molecules.
b. Fluorine forms negative ions.
c. Fluorine is less reactive than chlorine.
d. Silver fluoride will be sensitive to light.
Answers
1. d
2. d
3. d
4. b
5. c
6. a
7. d
8. c
9. c
10. d
11. b
12. d (Mg and Ca are in the same group in the Periodic Table)
13. d
14. d
15. d (Group I metals donate 1 outermost electrons to form X+ ions)
16. b
17. c
18. c (Chlorine, being more reactive than At, displaces At from its aqueous salt)
19. b
20. c
Worked Solutions
1. The elements below are all in Group I of the periodic Table.
element
symbol
electronic structure
lithium
Li
2, 1
sodium
Na
2, 8, 1
potassium
K
2, 8, 8, 1
rubidium
Rb
2, 8, 18, 8, 1
caesium
Cs
2, 8, 18, 18, 8, 1
a. Which element reacts most vigorously with cold water?
b. Write the formula of a caesium ion
c. How many protons are there in a rubidium ion?
d. Group I elements are very good conductors of electricity. Use a simple model of
the structure and bonding of the metal to explain this.
Solutions
a. Caesium
b. Cs+
c. 37
d. Metal consists of a lattice of cations in a sea of delocalised electrons. When a potential
difference is applied across the metal, the electrons flow towards the positive potential,
thereby conducting electricity.
2. This question is concerned with the following list of substances.
potassium
zinc oxide
lead(II) bromide
hydrogen
oxygen
carbon
Each substance can be used once, more than once, or not at all.
Name a substance from the list above which
a. reacts violently with water
b. conducts electricity when molten but not when solid
c. is amphoteric
d. has a formula of the type XY2
e. has an allotrope with a structure similar to that of silica
f. has a low melting point
g. is produced at the cathode during electrolysis of dilute sulphuric acid
Solutions
a. potassium
b. lead(II) bromide
c. zinc oxide
d. lead(II) bromide
e. carbon
f. oxygen
g. hydrogen
3. Chlorine, bromine, and iodine are elements in Group VII of the Periodic Table.
a. Describe how you would carry out a series of experiments to show the trend in reactivity
of these three elements, using the reagents below.
aqueous chlorine
aqueous bromine
aqueous iodine
aqueous potassium chloride
aqueous potassium bromide
aqueous potassium iodide
Your answer should include details of:
- which of the reagents you would use in each experiment
- a table showing the observations you would expect to see
- the equations for any reactions
b. Chlorine reacts with water to make a solution that can be used as a bleach. The equation
is show below
Cl2 + H2O ---> HCl + ClOH
Use oxidation numbers to show that chlorine is both oxidised and reduced in this reaction.
Solution
3a. A more reactive halogen would displace a less reactive halogen from its salt solution.
Displacement reactions are carried out to investigate the trend of reactivity of the halogens.
Add a few drops of chlorine water into a test tube containing 2cm3 of potassium chloride solution.
Record changes observed. The experiment is repeated with potassium bromide and potassium
iodide solution.
To find out the order of reactivity of the halogens, a second set of experiments is conducted with
bromine water added to test tubes containing 2cm3 of each of the salt solution provided and a third
set of experiments conducted with iodine solution added to 2cm3 of each of the salt solution.
The results are shown below:
Halogen
added
Cl2 (aq)
KCl
KBr
-
Br2 (aq)
No displacement
reaction
No displacement
reaction
Colourless solution turned Colourless solution turned
brown. Br2 formed
reddish brown. I2 formed
Colourless solution turned
reddish brown. I2 formed
No displacement reaction -
I2 (aq)
KI
Equations:
Cl2 + 2KBr ---> 2KCl + Br2
Cl2 + 2KI ---> 2KCl + I2
Br2 + 2KI ---> 2KBr + I2
3b. Chlorine is oxidised to ClOH and reduced to HCl at the same time. In the oxidation process,
oxidation number of chlorine increased from 0 in Cl2 to +1 in ClOH.
In the reduction process, oxidation number of chlorine decreased from 0 in Cl2 to -1 in HCl.
4a. The reaction of aluminium chloride with water is as follows:
2AlCl3 + 6H2O ---> 2Al(OH)3 + 6HCl
Each of the following compounds



aluminium bromide (AlBr3)
aluminium nitride (AlN)
aluminium carbide (Al4Cl3)
reacts with water in a similar way. Predict the formula of the compound produced, other
than aluminium hydroxide in each case.
b. NaNO3 NH3 CuSO4 MgCO3 Al2O3
Choose from the above list of compounds one which contains:
i. an element found in Group II of the periodic table
ii. a metallic element showing an oxidation number of +3
iii. a non-metallic element showing an oxidation number of -3
iv. a non-metallic element showing an oxidation number of +5
Solution
4a.
aluminium bromide: HBr produced
aluminium nitride: NH3 produced
aluminium carbide: CH4 produced
4bi. MgCO3
4bii. Al2O3
4biii. NH3
4biv. NaNO3
5. The Periodic Table is arranged in groups.
a. Rubidium (Rb) is in Group I of the Periodic Table. It reacts with water according to the
equation below
2Rb (s) + 2H2O (l) --> 2RbOH (aq) + H2 (g)
Predict what you would see when a small piece of rubidium is added to cold water.
b. Chlorine is in Group VII of the Periodic Table. Chlorine, Cl2, reacts with aqueous sodium
bromide.
i. Predict what you would see in this reaction.
ii. Write a balanced equation for this reaction.
Solution
5a. Rubidium will react violently with cold water. It melts into a silvery ball, effervesces and
releases a lot of heat and light energy.
5bi. The colourless solution of sodium bromide will react with the yellowish green chlorine gas to
form a solution that is reddish brown in colour.
5bii. Cl2 + 2Br- --> 2Cl- + Br2
6. Chlorine, bromine and iodine are elements in Group VII of the Periodic Table.
a. Describe the trend in colour and physical state at room temperature and pressure as the
atomic number increases.
b. Aqueous chlorine is an oxiding agent.
i. Name the products formed and write the ionic equation for the reaction between aqueous
chlorine and aqueous potassium bromide.
ii. Name the product formed when aqueous chlorine reacts with aqueous iron(II) chloride.
Solution
6a. As atomic number increases down the group, the physical states change from gas (fluorine and
chlorine) to liquid (bromine) and then to solid (iodine, astatine). The colour intensity also
increases from pale yellow (fluorine) to yellowish green (chlorine) and then to red-brown
(bromine) and finally to black (iodine and astatine).
6bi. Chloride and bromine.
2Br- + Cl2 --> 2Cl- + Br2
6bii. iron(III) chloride