Answer: The correct answer is Option a.
Step-by-step 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.