Chapter 8

Journey Inside the Atom

CBSE Class 9

Science Solutions

Question:

An atom ${}^{70}\mathrm{X}$ has 31 electrons. How many neutrons are there in its nucleus?

Answer: Verified

Since the atom is neutral, the number of protons is also 31.

Mass number (A) = Number of protons + Number of neutrons

70 = 31 + Number of neutrons

Number of neutrons = 70 - 31 = 39

Therefore, the nucleus contains 39 neutrons.

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(All Q's of this Chapter solved)

More NCERT Questions

Identify the number of electrons in the outermost shell of the following elements: (A) 612C(B) 919F(C) 1428Si [Pg. No. 152] If a bromine atom is available in the form of, say two isotopes, 3579Br (49.7\%) and 3581Br (50.3\%), calculate the average atomic mass of the bromine atom. [Pg. No. 156] Write the electronic configuration of the elements having atomic numbers 12, 16 and 18. [Pg. No. 152] Two different atoms have 11 protons each, but one has 12 neutrons, and the other has 13 neutrons. How do their atomic numbers and mass numbers compare? Are they the same element or different elements?