Ch 2.2 Molecular Elements and Compounds
Molecular element:
pure substance composed of molecules
made up of two or more atoms of the same element (ex.
Ozone, O3)
Diatomic elements: made up of two atoms (ex. N2, Br2)
Molecular Compound:
a pure substance made up of two or
more non-metals
Covalent Bond: sharing an electron pair
Drawing Lewis Structures and Structural Formulas for
Molecular Compounds
Bonding Capacity
number of electrons lost, gained or
shared by an atom when it bonds chemically
Group
1
2
13
14
15
16
17
18
Element Na
Ca
Al
C
N
O
Br
Ar
Bonding
Capacity
*Element with highest bonding capacity has centered position*
1) Count valence electrons (for polyatomic ions add electrons
for negative charge)
Eg. SO3
2) Place Symbols: (highest bonding capacity in the middle)
3)
Place bonding electrons around central atom (do not
exceed the bonding capacity)
4) Place lone pairs (outer atoms first)
5) If octet rule not followed move lone pairs
* Coordinate covalent bond*- when bonding capacity is
exceeded
HOMEWORK:
1)
Draw Lewis structures and structural formulas for each of the following molecules
a)
H2(g)
d) NF3(g)
b) O3(g)
e) N2H2(g)
c) OF2(g)
f) P2H4(g)
2) Draw Lewis structures and structural formulas for each of the following
polyatomic ions
a)
PO43-(aq)
b) OH-(aq)
c) BrO3-(aq)
d) ClO4-(aq)
3) Which of the Lewis structures un questions 2 and 3 include coordinate covalent
bonds?