NCERT Class 10 Chapter 4 Classification of Elements CBSE Board Sample Problems Very Short Answer

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Question

Which element was named as Eka-aluminium earlier?

Solution

Gallium

Question

According to which periodic law, every eight element repeat its property?

Solution

Newland’s Octave

Question

An element ‘X’ has mass number 35 and the number of neutrons is 18. Identify the group number and period of ‘X’

Solution

Mass Number= Protons + Neutrons

Number of protons =17, therefore Atomic number of ‘X’=l 7

Hence ‘X’ belongs to 3Id period and 1 7” group.

Question

How does valency vary across the period?

Solution

The valency first increases and then decreases to zero across the period.

Question

Out of Lithium and Potassium, which one has strong metallic character and why?

Solution

Potassium is more metallic as the metallic character increases down the group.

Question

What happens to the metallic character of elements as we move from left to right in a period?

Solution

It decrease from left to right in a period.

Question

Which period and group of the periodic table does an element with atomic number 4 belong to?

Solution

This element belongs to group 2 and period 2 of the periodic table.

Question

Why does Neon show extremely low reactivity?

Solution

Neon shows low reactivity because its outermost shell is completely filled.

Question

State Newlands’ law of octaves.

Solution

According to Newlands’ law of octaves when the elements are arranged in order of increasing atomic weights then every eighth element has properties similar to that of the first element.