ACTIVITY 4. Use of Sets of Illustrative Examples
In writing formulas of molecular compounds, use Greek prefix(es) to determine
number of atoms of each element in formula. Get elements and number of atoms of each from
name:
Illustrative Examples Set 1:
tetraphosphorus hexasulfide
dibromoheptoxide
P4S6
Br2O7
In writing formulas of acids, given an anion, we can get formula of acid by: adding H atoms
equal to negative charge on ion
Illustrative Examples Set 2:
F= fluoride ion (add # of H's equal to negative charge)
NO2– = nitrite ion (add # of H's equal to negative charge)
SO4–2 = sulfate ion (add # of H's equal to negative charge)
Formula: HF (aq)
Formula: HNO2 (aq)
Formula: H2SO4 (aq)
In writing formulas and names of acids, given an anion, we can name for acid:
depending on suffix of anion name.
Illustrative Examples Set 3:
1. If anion name ends with “–ide”, add prefix hydro and change “–ide” to “–ic” and add the
word acid.
Example:
HF (aq)
(anion name for F-1 is fluoride )
HF (aq)
= hydrofluoric acid
2. If anion name ends with “–ite”, change “–ite” to “–ous” and add the word acid.
Example:
HNO2 (aq)
(anion name for NO2-1 is nitrite)
HNO2 (aq)= nitrous acid
3. If anion name ends with “-ate”, change “-ate” to “-ic” and add the word acid.
Example:
H2SO4 (aq)
(anion name for SO42- is sulfate)
H2SO4 (aq)= sulfuric acid