Determine the number of electrons from the electron configuration.

From the previous problem, the electron configuration of the atom is $1s^2 2s^2 2p^6 3s^2$.
The total number of electrons in this atom is the sum of the superscripts:

$$2 + 2 + 6 + 2 = 12 \text{ electrons}$$

For a neutral atom, the number of protons is equal to the number of electrons.
Therefore, the number of protons in this atom is 12.

b) Number of protons:

$$\boxed{\text{}12\text{}}$$

The atomic number (Z) is defined as the number of protons in the nucleus of an atom.
Since the atom has 12 protons, its atomic number is 12.

c) Atomic number:

$$\boxed{\text{}12\text{}}$$