Which one of the following is a correct electronic configuration of sodium ? (a) 2,8 (b) 8, 2, 1 (c) 2, 1, 8 (d) 2, 8, 1

>

>

Chapter 4 NCERT Class 9 Science SOLUTIONS

18. Which one of the following is a correct electronic configuration of sodium ? (a) 2,8 (b) 8, 2, 1 (c) 2, 1, 8 (d) 2, 8, 1

Question:

Which one of the following is a correct electronic configuration of sodium ?

(a) 2,8 (b) 8, 2, 1

(c) 2, 1, 8 (d) 2, 8, 1

Answer:

(d) 2, 8, 1

More NCERT Questions

Download Free PDF

(All Q's of this Chapter solved)

question pointer

Complete the following table:

question pointer

Number of valence electrons in Cl– ion are— (a) 16 (b) 8 (c) 17 (d) 18

question pointer

Isotopes of an element have (a) the same physical properties (b) different chemical properties (c) different number of neutrons (d) different atomic numbers

question pointer

Rutherford’s alpha particle scattering experiment was responsible for the discovery of. (a) Atomic (b) Electron (c) Proton (d) Neutron

question pointer

For the following statements, write T for true and F for false.

question pointer

Composition of the nuclei of two atomic species X and Y are given below : Give the mass number of X and Y. What is the relation between the two species ?

question pointer

If Z = 3, What would be the valency of the element ? Also name the element.

question pointer

Na+ has completely filled K and L shells. Explain.

question pointer

Summarise the rules for writing of distribution of electrons in various shells for the first eighteen elements.

question pointer

Compare all the proposed models of an atom given in this chapter.

question pointer

What are the limitations of Rutherford’s model of the atom ?

question pointer

Describe Bohr’s model of the atom.

question pointer

What are the limitations of J.J. Thomson’s model of the atom?

question pointer

Write the electronic configuration of any one pair of isotopes and isobar

question pointer

For the Symbol H, D and T tabulate three sub-atomic particles found in each of them.

question pointer

With the help of given find out the mass number of oxygen and sulphur atom.

question pointer

If number of electrons in an atom is 8 and number of protons is also 8, then (i) What is the atomic number of the atom? (ii) What is the charge on the atom?

question pointer

If the K and L shells of an atom are full, then what would be the total number of electrons in the atom?

question pointer

If K and L shells of an atom are full, then what would be the total number of electrons in the atom?

question pointer

Write the distribution of electrons in Carbon and Sodium atoms.

question pointer

Helium atom has an atomic mass of 4u and two protons in its nucleus. How many neutrons does it have?

question pointer

Name the three Sub-atomic particles of an atom.

question pointer

What do you think would be the observation if the a-particle Scattering experiment is carried out using a foil of a metal other than gold?

question pointer

Draw a Sketch of Bohr’s model of an atom with three shells.

question pointer

On the basis Rutherford’s model of an atom, which sub-atomic particle is present in the nucleus of an atom?

question pointer

On the basis of Thomson’s atomic model explain how the atom is neutral as a whole.

question pointer

What are canal rays?

© 2026, Agrawal Group of Publications All rights reserved.