1. A ____molecule____________________ is a group of two or more atoms that are
_______chemically_________________ bonded. Each
______element__________________ tends to acquire an electron configuration
similar to that of the _____noble gas___________________ closest to it in the
periodic table. Elements try to gain stability by following the ____octet
rule__________________. To follow the rule, elements such as the metals __give
up______________________ electrons, and elements such as the nonmetals
_____receive___________________ electrons. The electrons involved in these
exchanges are ___valence electrons_____________________.
neutral
b) In nature, atoms are electrically ________________________
. They have as
many positive electrical charges, called “________________________
protons
,” as
negative electrical charges, called “________________________.”
electrons
When an
atom loses or gains one or more electrons, an ________________________
ion
is
formed. If the atom loses one or more electrons, the resulting ion will be positive.
If it gains one or more electrons, the ion will be negative. It is possible to predict
the charge of an element in a solution from its place in the
________________________
periodic table
. For example, aluminum is in
________________________,
Group IIIA
and the ion it forms will be written as
3+
________________________
Al
.
polyatomic ions
groups of two or more
EST There are also ________________________:
chemically bonded atoms that become electrically charged after
gaining
________________________
or ________________________
losing
one or more
electrons.
chemical bonds
c) EST There are two main types of ________________________
between atoms:
covalent
ionic
________________________
bonds and ________________________
bonds.
Lewis notation
These bonds can be represented by ________________________
.
transfer
d) EST When an ionic bond is formed, there is a ________________________
of
one or more ________________________ from one atom to another, usually
electrons
metal
nonmetal
from a ________________________
to a ________________________.
The
result is ________________________
ions that attract one another. A covalent
oppositely charged
bond results from the ________________________
of one or more pairs of
sharing
electrons between two atoms. When the bond between two atoms is the result of
the sharing or transfer of one pair of electrons, it is called a
________________________
. If the sharing or transfer involves two pairs of
single bond
electrons, the bond is a ________________________. In some cases, three pairs
double bond
of electrons are involved, forming a ________________________.
triple bond
Is each of the following substances a molecule, an element or an ion? Check the
appropriate column.
Symbol
Molecule
Element
Ion
a) NaCl



b) HCl



c) Br2



d) MgCl2



e) F-



f) Fe



3. Draw a Lewis structure for each of the following molecules.
a) NaCl
b) F2
4. What type of chemical bond is formed by the following molecules?
a) OCl2
A covalent bond
b) MgF2
An ionic bond.
c) O2
A covalent bond
d) Na2O
e) CaCl2
An ionic bond
An ionic bond
5. What am I?
a) an atom with an electric charge
An ion
b) atoms shown and classified in the periodic table
Chemical elements
The _____chemical formula_____________________ of a
____molecule______________________ provides information on the nature of
the elements that compose it. Sometimes we have to add a
____subscript____________________ to a symbol to indicate the number of
atoms of that element.
nomenclature
b) The rules of ______________________
are used to name substances. In general,
e we start by naming the
for binary covalent compounds,
first
________________________ element in the compound. Then, we change the
name of the ________________________
element according to a table of
second
corresponding names for the elements when in binary molecules.
c) When two elements can be combined in more than one way, the prefix
mono“__________________________
” is used to avoid ambiguity. For example, we
use the name “carbon monoxide” to designate the CO molecule, and “carbon
dioxide” to designate the CO2 molecule. The names of
polyatomic
__________________________
ions are not changed.
d) Common names do not always follow the rules. For example, NaCl is often
referred to as
“table salt” instead of “__________________________
sodium chloride
,” and CH3COOH is called
“vinegar” instead of
acetic
acid
“__________________________
.”
2. How many atoms are there of each element in the following molecules?
a) SO2
1 sulphur atom and 2 oxygen atoms
b) SO3
1 sulphur atom and 3 oxygen atoms
c) N2O
2 nitrogen atoms and 1 oxygen atom
d) Cl2O6
2 chlorine atoms and 6 oxygen atoms
e) H2O
2 hydrogen atoms and 1 oxygen atom
Complete the table below with the name of the element as it would appear as the
second element in a binary molecule.
Name of the element
Name used in nomenclature
Iodine
Iodide
Oxygen
Oxide
Sulphur
Sulphide
Hydrogen
Hydride
4. Name the following molecules, using the rules of nomenclature for binary
compounds (covalent and ionic).
a) HCl
Hydrogen chloride
b) CCl4
Carbon tetrachloride
c) CuF2
Copper fluoride
d) AuI
Gold iodide
e) CrBr3
Chromium bromide
f) NO2
Nitrogen dioxide
g) CoCl2
Cobalt chloride
h) KBr
Potassium bromide
i)
ZnI2
Zinc iodide
j)
PbO2
Lead dioxide
5. Write the chemical formulas for the following compounds, using the rules of notation
for binary compounds.
a) k)
dichloride
b) aluminum nitride
Cl2
c) d’aluminium
carbon dioxide
CO2
d) magnesium sulphide
MgS
e) mercury bromide
HgBr2
f) boron trichloride
BCl3
g) potassium sulphide
K 2S
h) beryllium chloride
BeCl2
i)
cesium selenide
Cs2Se
j)
sodium fluoride
NaF
AlN
6. Write the chemical formula for the molecule that would result from uniting each of the
following pairs of substances.
a) magnesium and bromine
MgBr2
b) sulphur and calcium
CaS
calcium
c) aluminum and oxygen
Al2O3
d) phosphate and sodium
Na2PO4
e) beryllium and nitrate
Be(NO3)2
f) oxygen and bromine
Br2O