A particular element (A) has one electron in its third shell. There is another element (B). Class 9

A particular element (A) has one electron in its third shell. There is another element (B). Class 9

Revise, Reflect, Refine (Page 181-183)

Question 1.

A particular element (A) has one electron in its third shell. There is another element (B) with six electrons in its second shell. Class 9

(i) How many electrons does A tend to give or take to become stable?

(ii) What kind of ion would it form?

(iii) How many electrons does B tend to give or take to become stable?

(iv) What kind of ion would it form?

(v) If A and B were to combine, what kind of bond would be formed?

(vi) What would be the formula for the compound thus formed?

Answer:

Element A has 1 electron in its third shell → Electronic configuration: 2, 8, 1. This is sodium (Na).

Element B has 6 electrons in its second shell → Electronic configuration: 2, 6. This is oxygen (O).

(i) Element A (Na) has 1 valence electron. It tends to give 1 electron to become stable (achieving the configuration of neon: 2, 8).

(ii) By losing 1 electron, A forms a cation with a charge of +1. It would form Na⁺ (a positively charged ion / cation).

(iii) Element B (O) has 6 valence electrons. It needs 2 more to complete its octet. It tends to take 2 electrons to become stable.

(iv) By gaining 2 electrons, B forms an anion with a charge of 2-. It would form O^2- (a negatively charged ion / anion).

(v) If A (Na) loses an electron and B (O) gains electrons, the bond formed is an ionic bond (electrostatic force of attraction between the oppositely charged ions Na⁺ and O^2-).

(vi) A = Na⁺ (valency 1), B = O^2- (valency 2).

Formula: Na₂O (sodium oxide)