What is the maximum number of electrons that can occupy the d sublevel?

10

Explanation:

The electron configuration for an element follows some rules:

K 1s2 (2 electrons)

L 2s2 sp6 (8 electrons)

M 3s2 3p6 3d10 (18 electron)

N 4s2 4p6 4d10 4f14 (32 electron)

and so on...

But you don't do it linearly, you go 1s, 2s, 2p, 3s, 3p, 4s, 3d

And you can follow some rules if you have 24 electrons, for example, the sequence should go 1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5

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

a. by the combination of an unlimited number of elements