Download BLB – Chapter 2 Atoms, Molecules, and Ions

BLB – Chapter 2
Atoms, Molecules, and Ions
Note: Many images are from “Chemistry, The
Central Science”, 9th Ed., by Brown, LeMay, and
Bursten.
Atoms
- smallest unit in a reaction
- building blocks of elements
Molecules
- building blocks of compounds
Ions
- building blocks of ionic compounds.
Dalton’s atomic theory
- 4 postulates
- basic grammar of chemistry
#1. Provides the definition of atom
#2. Explains the identity of atom
#3. Explains the Law of conservation of atoms
in a chemical reaction
#4. Explains an atom’s function in compound
formation
Discovery of the subatomic particles e-, p+,no
location
Electrons
Protons
Neutrons
mass
charge
Radioactivity – why does it happen?
Alpha, a, particles, 42He2+: mass = 4 amu
charge = 2+
Beta, b, particles, 0–le: mass = 0.00055 amu
charge = 1–
Gamma, g, particles: photons with no mass
or charge
Modern view of atomic structure:
Particle
Proton
Neutron
Electron
Charge
1+
None
1–
Mass (amu)
1.0073
1.0087
5.486 x 10–4
Isotopes
Name
hydrogen, 1H
deuterium, 2H
tritium, 3H
Proton
1
1
1
Electron
1
1
1
Neutron
0
1
2
Atomic number, Z: (no. of p+)
Mass number, A: (no. of p+ + no. of no)
Nuclear symbol,
A
Z
X
# neutron = mass # (A) – atomic # (Z)
Problem 17. Fill in the gaps in the following table,
assuming each column represent a neutral atom.
Symbol
Protons
Neutrons
Electrons
Mass#
52Cr
?
?
?
?
32
42
?
?
?
?
20
20
?
?
?
?
86
222
?
77
?
?
193
Atomic weights: Atomic mass scale
1 amu = 1.66054 x 10–24 g
1 g = 6.02214 x 1023 amu
Average atomic weight and Isotopic abundance
Problem 23.
Pb consists of four naturally occurring
isotopes with masses (amu):
203.97302; 1.4% abundance
205.97444; 24.1% abundance
206.97587; 22.1 % abundance
207.97663; 52.4% abundance
Calculate the average atomic weight of lead.
The periodic table (rows and columns)
Color codes in the periodic table
Characteristics of:
Metals Nonmetals Metalloids Main group elements Alkali metals Alkaline earth metals Noble gases Halogens Chalcogens Transition metals -
Problem 31. For each of the following elements,
write its chemical symbol determine the name of
the group to which it belongs, and indicate whether
it is a metal, metalloid, or nonmetal
Element
a)
b)
c)
d)
e)
Potassium
Iodine
Magnesium
Argon
Sulfur
Symbol
Group
nonmetal
metalloid
or Metal
Molecules and chemical formulas –
Molecular and empirical formulas –
Molecular formula and structural formula –
Problem 37. How many hydrogen atoms are
there in each of the following?
a) C2H5OH
b) Ca(CH3COO)2
c) (NH4)3PO4
Problem 41. Write the empirical formula
corresponding to each of the following molecular
formulas:
a) Al2Br6
b) C3H8
c) C4H8O2
d) P4O10
e) C6H4Cl2
f) B3N3H6
Ions and ionic compounds –
Cations – positively charged ions. (Other
characteristics?)
Anions – negatively charged ions. (Other
characteristics?)
Monatomic ion – only one atom in the
species. (Consult the periodic table.)
Polyatomic ion – more than one atom in the
species. (Memorize the list on Table 2.5.)
Problem 43. Predict the charge of the monatomic
ion of each, using a periodic table:
a) Al
b) Ca
c) S
d) Cs
How to write the chemical formulas of
ionic compounds?
– cations followed by anions
– cross over of the charges as subscripts
Mg
2+
N
3-
Mg3N2
Problem 45. Using the periodic table to guide
you, predict the formula and name of the
compound formed by the following elements:
Elements
a) Ga and F
b) Li and H
c) Al and I
d) K and S
Formula
Name
Problem 47. Predict the empirical formula for the
ionic compound formed by
a) Ca2+ and Br–
b) NH4+ and Cl–
c) Al3+ and C2H3O2–
d) K+ and SO42–
e) Mg2+ and PO43–
Problem 49. Predict whether each of the following
compounds is molecular or ionic:
a) B2H6
b) CH3OH
c) LiNO3
d) Sc2O3
e) CsBr
f) NOCl
g) NF3
h) Ag2SO4
Naming inorganic ionic compounds
Cations:
- Names are the same as the metals, end in “-ium”.
Consult Table 2.4.
- If multiple charges are possible, use Roman numeral
to indicate the charge.
Fe2+ is iron(II) or ferrous
Fe3+ is iron(III) or ferric
Common in transition and post transition metals.
An important polyatomic cation is NH4+ (ammonium)
Anions:
- Monatomic ions
stem name plus “-ide”
H– is hydride
N3– is nitride.
- Polyatomic anions containing oxygen (called
oxyanions) have names ending with “-ate” or “ite”.
NO2– nitrite
NO3– is nitrate.
Anions:
- With halogens, oxyanions use prefixes of
“per-”
“hypo-”
ClO4– is perchlorate
ClO3– is chlorate
ClO2– is chlorite
ClO– is hypochlorite.
-
Anions:
- adding H+ to an oxyanion
add the prefix “hydrogen” of “dihydrogen”.
HCO3– is hydrogen carbonate (or bicarbonate),
H2PO4– is dihydrogen phosphate.
Consult Table 2.5.-
Naming ionic compounds –
The name of the cation is followed by the
name of the anion.
CaCl2 is calcium chloride, Cu(ClO4)2 is
copper(II) perchlorate (or cupric
perchlorate).
Names and formula of acids –formulas start with a
hydrogen atom.
a. Acids based on anions whose names end with
–ide:
“hydro-” as prefix and “-ic” as ending.
HCl is hydrochloric acid
H2S is hydrosulfuric acid.
b. Acids based on anions whose names end with –ate or –ite: “--”ate” anion ends in “-ic” as an acid SO42- ; H2SO4
“-ites” anions ends in “-ous” as an acid SO32- ;H2SO3
Naming binary molecular compounds –contain
only two types of atoms.
- element farthest to the left in the periodic table usually is
written first. The more electronegative atom comes second
and ends in “ide”.
- for elements in the same group, the lower one is named
first. More electronegative atom comes second and ends
in –“ide”
- Greek prefixes are used to indicate the number of atoms
of each element.
1 = mono, 2 = di, 3 = tri, 4 = tetra, 5 = penta,
6 = hexa, 7 = hepta, 8 = octa, 9 = nona, 10 = deca
Problem 51. Write the chemical formula for
a) chlorite ion
b) chlorate ion
c) perchlorate ion
d) hypochlorite ion
Problem 53. Write the chemical name of the
following ionic compounds.
Chemical formula
Chemical name
a) AlF3
b) Fe(OH)2
c) Cu(NO3)2
d) Ba(ClO4)2
e) Li3PO4
f) Hg2S
g) Ca(C2H3O2)2
h) Cr2(CO3)3
i) K2CrO4
j) (NH4)2SO4
Problem 55. Write the chemical formulas of the
following compounds.
Chemical name
a) copper(I) oxide
b) Potassium peroxide
c) Aluminum hydroxide
d) Zinc nitrate
e) Mercury(I) bromide
f) Iron(III) carbonate
g) Sodium hypobromite
Chemical formula
Problem 57. Write the chemical formula or name,
as appropriate, for each of the following acids:
Chemical formula
HBrO3
HBr
H3PO4
…………………
…………………
…………………
Chemical name
…………………
..………………..
…………………
Hypochlorous acid
Iodic acid
Sulfurous acid
Problem 59. Write the chemical name or formula,
as appropriate, for the following molecular
substances:
Chem. formula
Chem. Name
SF6
…………………………………
IF3
…………………………………
XeO3
…………………………………
…………….
Dinitrogen tetroxide
……………..
Hydrogen cyanide
……………..
Tetraphosphorus hexasulfide
Problem 61. Write the chemical formula of each
substance mentioned in the following word
descriptions.
a) Zinc carbonate can be heated to form zinc oxide and
carbon dioxide.
b) On treatment with hydrofluoric acid silicon dioxide forms
silicon tetrafluoride and water.
c) Sulfur dioxide reacts with water to form sulfurous acid.
d) The substance hydrogen phosphide, commonly called
phosphine, is a toxic gas.
e) Perchloric acid reacts with cadmium to form cadmium(II)
perchlorate.
f) Vanadium(III) bromide is a colored solid.
Problem 76. The element oxygen has three
naturally occurring isotopes, with 8, 9, and 10
neutrons in the nucleus, respectively.
a) Write the full chemical symbols for these three
isotopes.
b) Describe the similarities and differences
between the three kinds of atoms of oxygen.
Problem 87. Name each of the following oxides.
Assuming that the compounds are ionic, what
charge is associated with the metallic element in
each case?
Formula
a) NiO
b) MnO2
c) Cr2O3
d) MoO3
Chemical name
Charge on the
metal atom
Problem 90. Write the chemical names and
formula of the following substances:
Common
name
a) Table salt
b) Smelling salt
b) Baking soda
b) Washing soda
b) Caustic soda
b) Caustic potash
b) Plaster of Paris
b) Muriatic acid
b) Battery acid
Chemical
name
Chemical
formula