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Choose an element from period 3 of modern periodic table that matches the
description given below in each instance. Give reason for your choice.
a. It has a similar structure to diamond.
b. It has same valency as Lithium.
c. It has variable valency and is a member of the Oxygen family (group 16).
Answer
We know that third period of Periodic table has 8 elements
Sodium (Na), Magnesium (Mg), Aluminium (Al), Silicon (Si), Phosphorus (P), Sulfur (S), Chlorine (Cl),and Argon (Ar).
as shown below
Out of this,
a. Silicon has similar structure to Diamond
Explanation-
We know that, Diamond is an allotrope(form) of Carbon
And Carbon and Silicon are similar because fo following reasons
Both have Valency of 4 (Tetravalent)
Both form covalent bonds
Both do Catenation (ability to self combine and form long chain)
Both have tetrahedral structure (Each atom is joined by 4 other atoms)
b. Sodium has same valency as Lithium
Explanation
We know that
Lithium has Valency of 1
Sodium also has Valency of 1 (Lies in first period(
Hence, Answer is Sodium
c. It has variable valency and is a member of the Oxygen family (group 16).
Explanation
Oxygen Family refers to chemical elements lying in Group 16
These include elements like
Oxygen, Sulphur, Selenium, Tellurium and Polonium
All these have 6 electrons in outermost shell
Out of this, Sulphur lies in third period
Valency of Sulphur
Sulphur has 6 electrons in outermost shell, so it needs 2 more to become stable
hence, Valency of Sulphur is 2
However, sometimes it shows Multiple Valencies also
Example
In Case of SO2,It shows Valency of 4
In Case of SO3,I shows Valency of 6
Hence, Sulphur is a Metal which belongs to Oxygen Family (Group 16) and has multi valency and belongs to O
