Diatomic Gases, Compound Names and Formulae
Diatomic Gases
Write the name or chemical formula of the following diatomic gases.
Hydrogen gas
O2
Nitrogen gas
Cl2
Fluorine gas
Compound Names
In general, the name of a compound is the name of the first element followed by the name
of the second element (with an –ide) at the end. E.g. KCl = potassium chloride
BaO
SiC
AlN
BeI2
BP
ZnCl2
CaO
KI
Ag2O
Ra3As2
HI(g)
Li4C
H2O
Cr2O3
NaH
B4C3
HCl(g)
Formulae – the Criss-cross rule:
1. To determine the formula of a compound, find the valence of each element.
e.g. magnesium chloride = Mg2+Cl-1
2.
3.
Use the criss-cross rule to write the proper subscripts in the formula. (Note that
ones are implied and do not need to be written). E.g. MgCl2
If the valences are the same, they ‘cancel’ out. E.g. Mg2+O2- = MgO
4. Valences that can be ‘reduced’ should be reduced, e.g. Mg2+C-4 = MgC2
1. magnesium bromide
7. silver chloride
2. aluminum carbide
8. barium hydride
3. boron chloride
9. chromium phosphide
4. calcium sulphide
10. silicon bromide
5. potassium fluoride
11. silicon arsenide
6. zinc oxide
12. hydrogen oxide