Question 1 - Past Year - 5 Mark Questions - Chapter 5 Class 10 - Periodic Classification of Elements

The position of certain elements in the Modem Periodic Table are shown below:

Using the above table answer the following questions giving reasons in each case:

(i) Which element will form only covalent compounds?

(ii) Which element is a non-metal with valency 2?

(iii) Which element is a metal with valency 2?

(iv) Out of H, C and F which has largest atomic size?

(v) To which family does H, C and F belong?

Answer   

(i)

Element E (silicon) belongs to group 14 and period 3.

Electronic configuration of E: 2, 8, 4

Number of Valence electrons = 4

Since it has 4 electrons in its outermost shell , it can neither gain electrons nor lose electrons as it will become unstable.

So, it forms covalent bonds (by sharing electrons).

(ii)

Electronic configuration of B: 2, 8, 6

Number of valence electrons = 6

Valency = 2

Since, B has valency 2, it gains 2 electrons to become stable.

Metals lose electrons to become stable whereas, non-metals gain electrons to become stable.

So, element B(oxygen) is a non-metal with valency 2.

(iii)

Electronic configuration of D: 2, 8, 2

Number of valence electrons = 2

Valency = 2

Since, D has valency 2, it will lose 2 electrons to become stable.

Metals lose electrons to become stable whereas, non-metals gain electrons to become stable.

So, element D(magnesium) is a metal with valency 2.

(iv)

H, C and F all belong to the same group. Element F comes below C and H.

So, element F(argon) has the largest atomic size . 

(v)

H, C and F belong to group 18 which means their octet is complete and these elements are stable. 

Elements with filled octet belong to the noble gas family.