How many completely full sublevels are in a neutral atom of magnesium?

4 sublevels are completely filled.

Explanation:

Magnesium is present in group 2.

Its atomic mass is 24 g/mol.

Its atomic number is 12.

It is alkaline earth metal.

Electronic configuration of Mg:

Ma₁₂ = 1s² 2s² 2p⁶ 3s²

From above given electronic configuration we can see all sublevels are completely filled.

The 1st energy level have one sub level (1s)  which is completely filled, 2nd energy level have 2 sublevel (2s and 2p) and 3rd energy level have one sublevel (3s) completely filled. So all are completely filled.

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements