Define valency of an element. What is the valency of:Aluminium in aluminium sulfateSodium in sodium sulfate

Valency, also known as oxidation state, is a measure of the ability of an atom of an element to combine with other atoms. It represents the number of electrons that an atom can gain, lose, or share when it forms chemical compounds with other atoms. Valency is typically determined by the number of valence electrons an atom has.

For elements in the main group of the periodic table (groups 1, 2, and 13-18), the valency is often related to the number of electrons an atom needs to gain or lose to achieve a stable, full outer electron shell (usually eight electrons for most elements). Here's how it works:

Group 1 elements (alkali metals like sodium) have a valency of +1 because they have one valence electron and tend to lose that electron to achieve a stable electron configuration similar to the noble gas neon.

Group 13 elements (including aluminum) have a valency of +3 because they have three valence electrons and can lose those three electrons to attain a stable electron configuration.

Now, let's determine the valency of aluminum in aluminum sulfate (Al2(SO4)3) and sodium in sodium sulfate (Na2SO4):

Aluminum in aluminum sulfate (Al2(SO4)3):
Aluminum (Al) has a valency of +3, as mentioned earlier. In aluminum sulfate, there are two aluminum atoms, each contributing a valency of +3. So, the total valency contributed by aluminum in aluminum sulfate is +3 (from each Al) * 2 (number of Al atoms) = +6.

Sodium in sodium sulfate (Na2SO4):
Sodium (Na) has a valency of +1, as it belongs to Group 1 of the periodic table. In sodium sulfate, there are two sodium atoms, each contributing a valency of +1. So, the total valency contributed by sodium in sodium sulfate is +1 (from each Na) * 2 (number of Na atoms) = +2.

In summary:

The valency of aluminum in aluminum sulfate is +6.
The valency of sodium in sodium sulfate is +2.