Consider the element sodium. it's atomic number is and equals a.11; the number of protons b.12; the number of neutrons c.23; the sum of protons and neutrons d.23; the number of electrons

The correct answer is Option a.

Explanation:

Atomic number is defined as the number of protons or number of electrons that are present in neutral atom.  It is represented as Z.

Z = Atomic number = Number of protons = Number of electrons

Sodium is the 11th element of the periodic table. The atomic number of this element is 11.

So, in a neutral element of sodium, the number of protons and electrons are 11.

Hence, the correct answer is Option a.