Periodic Classification of Elements NCERT Solution, study material, CBSE Notes

NCERT Solution: Periodic Classification of Elements

If an element X is placed in group 14, what will be the formula and the nature of bonding of its chloride?

If an element is placed in group 14, then it has 4 electrons in its outermost orbit. Hence, the formula of its chloride is ECl₄. Since the element can make compound by sharing of electrons, so its compound will have covalent bond.

Compare the radii of two species X and Y. Give reasons for your answer.

Compare the radii of two species X and Y. Give reasons for your answer.
(a) X has 12 protons and 12 electrons
(b) Y has 12 protons and 10 electrons
Ans. The atomic radius of X is greater than that of Y. While, X is the element with equal number of protons and electrons, Y is its ion after the loss of two electrons. For the same element, atomic radius of ion is less than that of the electroneutral element.

Arrange the following elements in increasing order of their atomic radii.

Arrange the following elements in increasing order of their atomic radii.
(a) Li, Be, F, N
Ans. Li >Be>F>N
These elements are in same period and are arranged from left to right.
(b) Cl, At, Br, I
Ans. Cl<Br<I<At
These elements are in same group and are arranged from top to bottom.

Identify and name the metals out of the following elements whose electronic configurations are given below.

Identify and name the metals out of the following elements whose electronic
configurations are given below.
(a) 2, 8, 2
Ans. Magnesium
(b) 2, 8, 1
Ans. Sodium
(c) 2, 8, 7
Ans. Non-metal
(d) 2, 1
Ans. Lithium

Write the formula of the product formed when the element A (atomic number 19) combines with the element B (atomic number 17). Draw its electronic dot structure. What is the nature of the bond formed?

The formula of product formed by A and B is AB.
Electronic configuration of A: 2, 8, 8, 1
Electronic configuration of B; 2, 8, 7
They would make compound by forming ionic bond. Electronic dot structure is as follows:

Arrange the following elements in the increasing order of their metallic character Mg, Ca, K, Ge, Ga

Ge<Ga<Mg<Ca<K

Identify the elements with the following property and arrange them in increasing order of their reactivity

(a) An element which is a soft and reactive metal
Ans. Sodium
(b) The metal which is an important constituent of limestone
Ans. Calcium
(c) The metal which exists in liquid state at room temperature
Ans. Mercury

Properties of the elements are given below. Where would you locate the following elements in the periodic table?

(a) A soft metal stored under kerosene
Ans. Sodium Group 1, Period 3
(b) An element with variable (more than one) valency stored under water.
Ans. Phosphorus Group 15, Period 3
(c) An element which is tetravalent and forms the basis of organic chemistry
Ans. Carbon Group 14, Period 2
(d) An element which is an inert gas with atomic number 2.
Ans. Helium Group 18, Period 1
(e) An element whose thin oxide layer is used to make other elements corrosion resistant by the process of “anodising”
Ans. Aluminum Group 13, Period 3