Grade-10 Science
Name and Formula of Simple Ionic Compound -Handout for instruction
Lesson objective:
To learn about writing formula of simple ionic compounds
Language objective:
Read the background information given below, listen carefully to the
example discussed by the teacher, observe on the board and write the
examples discussed.
ATL Focus:
Communication
Critical Thinking
Background information:
Metal loses electron and forms a positive ion (Positive ion is called cation).
Non-metal gains electron(s) and forms negative ions called ‘anions’. Cations
and anions are strongly attracted by electrostatic forces and forms ‘ionic
compound’.
All group 1 metals form cation with one positive (plus) (+) charge. Positive
charge (+) is written on the top of the symbol of the metal as ‘superscript’,
for example sodium ion is written as Na+
All group 2 metals forms cation with two positive charges (2+), For example
– calcium ion is written as Ca2+. Transition metals forms ions with + or 2+
charge and it is given to you with the name by including roman number for
example, iron (II) means Fe2+. Group 13 metals have 3+ charge.
Non-metals form anions and have negative (minus) charge. Names of
simple anions ends with the suffix ‘ide’; For example name of anion
formed by chlorine is ‘chloride’ and it has 1- charge, formula of chloride ion
is Cl-. All the halogens (group-17) have one negative charge. Group 16
anions will have 2- charge, example- anion of oxygen is called ‘oxide’ and
its formula is O2- and Group 15 have 3- charge.
For writing names – Always write the name of cations first and then anion.
Example – Na+ and Cl- name is sodium chloride.
Steps for writing formula:
1. Find the correct symbol from the periodic table.
2. Write the symbol of cation (positive ion).
3. Then write the formula of anion.
4. Balance the number of + and – charge by adding more cations/anions
as required.
5. Write the number of additional ions as a ‘subscript’ after the formula.
6. Write the full formula (Do not include the charge of ions in the
formula of compound).
What to do next? – Try writing names and formula of simple ionic
compounds in the worksheet provided.