Which characteristic is given by the principal quantum number? < br />
a)orbital size< br />
b)orbital mass< br />
c)orbital shape< br />
d)orbital orientation

option a) orbital size.

Explanation:

The principal quantum number, n, is the level of energy. The bigger the number n the higher the energy. The higher the energy the farther away from the nucleus is located the electronic density. The farther away the electronic density the bigger the orbital. So, the principal quantum number accounts for the size of the orbital.