Question

Why does the black carbon ball have 4 holes while the white hydrogen ball only has one hole?

Answer 1

In atomic models balls represent an atom

Now if an atom like carbon has four holes it means it can bond with four atoms. It has valency = 4.

The atomic number of carbon is 6

the configuration is 1s2 2s2 2p2

So due to four valence electrons it can bind with four other atoms and thus we have four holes in carbon ball

The hydrogen show a valency of one

the atomic number of hydrogen = 1

its configuration is 1s1

So it can bind with one atom (max) thus we have one hole in hydrogen ball