What is the atomic mass of sodium ?

23

The correct answer is option (3) 23.

The atomic mass of sodium is 23.

1. Atomic Mass:  The atomic mass of an element is the average mass of its atoms, taking into account the abundance of different isotopes and their masses. It is expressed in atomic mass units (u) or unified atomic mass units (amu).

2. Isotopes of Sodium: Sodium (Na) has two stable isotopes: sodium-23 (\(^{23}_{11}Na\)) and sodium-24 (\(^{24}_{11}Na\)). However, sodium-23 is the dominant and more abundant isotope, constituting about 100% of naturally occurring sodium.

3. Calculation of Atomic Mass:

The atomic mass is calculated based on the abundance of each isotope and its respective mass. For sodium: 

Atomic Mass of Sodium (\(Na\)) = (Abundance of \(^{23}Na\) * Mass of \(^{23}Na\) ) + (Abundance of \(^{24}Na\) * Mass of \(^{24}Na\) )

Given that sodium-23 has an atomic mass of approximately 22.99 u, and sodium-24 has an atomic mass of approximately 23.99 u, the weighted average considering the abundance of these isotopes results in the commonly cited atomic mass of sodium as 23.