Question

A particular element (A) has one electron in its third shell. There is another element (B) with six electrons in its second shell.

1. How many electrons does A tend to give or take to become stable?
2. What kind of ion would it form? 
3. How many electrons does B tend to give or take to become stable? 
4. What kind of ion would it form? 
5. If A and B were to combine, what kind of bond would be formed?
6. What would be the formula for the compound thus formed?

Answer 1

• A is sodium (configuration 2,8,1): it tends to lose 1 electron, forming a cation, Na⁺.
• B is oxygen (2,6): it tends to gain 2 electrons, forming an anion, O²⁻.
• A and B combine by an ionic bond, giving the formula Na₂O.