Question

An element X with an atomic number 12 combines with an element Y of atomic number 17 to form a compound. Select the correct options that correspond to the formed compound.

i. The compound formed is ${XY}_2$.
ii. The compound consists of ionic bonds.
iii. The compound consists of covalent bonds.
iv. The compound has low melting and boiling points.

[1 mark]

• A. (i) and (iii)
• B. (i), (iii), and (iv)
• C. (i) and (ii)
• D. (iii) and (iv)

Answer 1

The correct option is C (i) and (ii)

Elements	Atomic numbers	Configuration
X	12	2,8,2
Y	17	2,8,7

The valency of element X is 2, and thus it can lose two electrons to achieve the nearest noble gas configuration.
The element Y, on the other hand, has a valency as 1. Thus, it needs to gain one electron to complete its octet.
So, two Y elements combine with one X element to form a compound ${XY}_2$.
As there is a transfer of electrons taking place, the compound contains an ionic bond, and thus, is an ionic compound.

Ionic compounds are held together by electrostatic forces, which require more energy to break. Higher the energy required to break the bond, more the melting and boiling points of the compound.