Ans: A)
The electron configuration of an element can be represented based on Aufbau principle according to which the electrons fill up from the lower to higher energy levels.
s orbitals can accommodate a maximum of 2 electrons
p orbitals = 6 e-
d orbitals = 10 e-
f orbitals = 14 e-
The atomic number for sodium (Na) = 11
The 11 electrons in Na can be arranged as follows:
Na[11] = 1s²2s²2p⁶3s¹
