Question

A nucleus is represented by the symbol \(_{Z}^{A}\textrm{X}\) has

• A. Z protons and A –Z neutrons
• B. Z protons and A neutrons
• C. A protons and Z –A neutrons
• D. Z neutrons and A –Z protons

Answer 1

The Correct Option is A

In nuclear physics, the notation \(_{Z}^{A}\textrm{X}\) is a standard way to represent a chemical element and its isotopes. This notation consists of three main parts:

• \(Z\): Represents the atomic number, which indicates the number of protons in the nucleus. Protons determine the identity of the element.
• \(A\): Represents the mass number of the nucleus, which is the total number of protons and neutrons combined.
• \(\textrm{X}\): Represents the chemical symbol of the element.

Therefore, for a nucleus represented by \(_{Z}^{A}\textrm{X}\):

• The number of protons is given directly by the atomic number \(Z\).
• The number of neutrons can be determined by subtracting the number of protons from the mass number: A - Z.

This leads us to the conclusion:

• Z protons and A - Z neutrons are present in the nucleus.

Let's reason why the other options are incorrect:

• Z protons and A neutrons: This implies that the mass number \(A\) is the count of neutrons only, which is incorrect since \(A\) is the sum of protons and neutrons.
• A protons and Z – A neutrons: This would suggest a nucleus with more protons than its mass number, which is impossible because the mass number includes all protons and neutrons.
• Z neutrons and A – Z protons: Protons, not neutrons, determine the chemical identity of the element \(X\). Hence, Z represents protons, not neutrons.

Based on this understanding, the correct answer is: Z protons and A – Z neutrons.