Question

molecular (covalent) compounds
when non - metal atoms share electrons with other non - metal atoms, they form basic units called molecules. compound composed of molecules are thus molecular (covalent) compounds. we shall learn the nomenclature of binary covalent compounds.
exercise: define a binary compound
case 4. binary covalent compounds
as with ionic compounds, the second atom in the formula gets an - ide ending.
unlike ionic compounds, the number of each atom is specified with a prefix (as there are no ions in a molecule)
these are the prefixes you need to know:
1 is mono-
2 is di-
3 is tri-
4 is tetra-
5 is penta-
6 is hexa-
7 is hepta-
8 is octa-
9 is nona-
10 is deca-
note: when there is only one atom of the first element, the mono prefix is omitted.
examples: nf3 nitrogen trifluoride
p4o10 tetraphosphorus decaoxide
i2s diiodine monosulfide
b2cl6 diboron hexachloride
exercise: name the following:
n2o4
pcl5
so2
so3
cs2
br2o7
co
p2o3
cl2o
sf6
exercise: give formulas for the following:
iodine pentabromide
chlorine dibromide
oxygen difluoride
carbon tetrachloride
sulfur hexafluoride
silicon dioxide
iodine heptafluoride
nitrogen monoxide
dinitrogen trioxide
also: you must remember these three very important common names:
h2o (water)
nh3 (ammonia)
ch4 (methane)

Explanation:

Step1: Define binary compound

A binary compound is a compound composed of two different elements.

Step2: Name $N_2O_4$

There are 2 nitrogen atoms (di - prefix) and 4 oxygen atoms (tetra - prefix), so it is dinitrogen tetroxide.

Step3: Name $PCl_5$

There is 1 phosphorus atom (prefix omitted) and 5 chlorine atoms (penta - prefix), so it is phosphorus pentachloride.

Step4: Name $SO_2$

There is 1 sulfur atom (prefix omitted) and 2 oxygen atoms (di - prefix), so it is sulfur dioxide.

Step5: Name $SO_3$

There is 1 sulfur atom (prefix omitted) and 3 oxygen atoms (tri - prefix), so it is sulfur trioxide.

Step6: Name $CS_2$

There is 1 carbon atom (prefix omitted) and 2 sulfur atoms (di - prefix), so it is carbon disulfide.

Step7: Name $Br_2O_7$

There are 2 bromine atoms (di - prefix) and 7 oxygen atoms (hepta - prefix), so it is dibromine heptoxide.

Step8: Name $CO$

There is 1 carbon atom (prefix omitted) and 1 oxygen atom (mono - prefix for oxygen), so it is carbon monoxide.

Step9: Name $P_2O_3$

There are 2 phosphorus atoms (di - prefix) and 3 oxygen atoms (tri - prefix), so it is diphosphorus trioxide.

Step10: Name $Cl_2O$

There are 2 chlorine atoms (di - prefix) and 1 oxygen atom (mono - prefix for oxygen), so it is dichlorine monoxide.

Step11: Name $SF_6$

There is 1 sulfur atom (prefix omitted) and 6 fluorine atoms (hexa - prefix), so it is sulfur hexafluoride.

Step12: Give formula for iodine pentabromide

Iodine is $I$, pentabromide means 5 bromine atoms, so the formula is $IBr_5$.

Step13: Give formula for chlorine dibromide

Chlorine is $Cl$, dibromide means 2 bromine atoms, so the formula is $ClBr_2$.

Step14: Give formula for oxygen difluoride

Oxygen is $O$, difluoride means 2 fluorine atoms, so the formula is $OF_2$.

Step15: Give formula for carbon tetrachloride

Carbon is $C$, tetrachloride means 4 chlorine atoms, so the formula is $CCl_4$.

Step16: Give formula for sulfur hexafluoride

Sulfur is $S$, hexafluoride means 6 fluorine atoms, so the formula is $SF_6$.

Step17: Give formula for silicon dioxide

Silicon is $Si$, dioxide means 2 oxygen atoms, so the formula is $SiO_2$.

Step18: Give formula for iodine heptafluoride

Iodine is $I$, heptafluoride means 7 fluorine atoms, so the formula is $IF_7$.

Step19: Give formula for nitrogen monoxide

Nitrogen is $N$, monoxide means 1 oxygen atom, so the formula is $NO$.

Step20: Give formula for dinitrogen trioxide

Dinitrogen means 2 nitrogen atoms ($N_2$), trioxide means 3 oxygen atoms, so the formula is $N_2O_3$.

Answer:

Define a binary compound: A compound composed of two different elements.
$N_2O_4$: Dinitrogen tetroxide
$PCl_5$: Phosphorus pentachloride
$SO_2$: Sulfur dioxide
$SO_3$: Sulfur trioxide
$CS_2$: Carbon disulfide
$Br_2O_7$: Dibromine heptoxide
$CO$: Carbon monoxide
$P_2O_3$: Diphosphorus trioxide
$Cl_2O$: Dichlorine monoxide
$SF_6$: Sulfur hexafluoride
Iodine pentabromide: $IBr_5$
Chlorine dibromide: $ClBr_2$
Oxygen difluoride: $OF_2$
Carbon tetrachloride: $CCl_4$
Sulfur hexafluoride: $SF_6$
Silicon dioxide: $SiO_2$
Iodine heptafluoride: $IF_7$
Nitrogen monoxide: $NO$
Dinitrogen trioxide: $N_2O_3$