Solution:  

Element x: Sulphur

Atomic number is 16

Atomic mass: 32.07 amu

Electronic configuration:

The 1s orbital can holds 2 electrons

The 2s orbital can holds 2 electrons

The 2p orbital can holds 6 electrons

The 3s orbital can holds 2 electrons

The 3p orbital can holds 4 electrons

Valency:

Sulphur exhibits variable valency of 2,4,6. Variable valency occurs when an element shares, donates or accepts electrons in the various proportions to combine with the other atoms according to the nature of the reaction.