Silicon's electron configuration is 1s2, 2s2, 2p2
We can see that there are 3 sub-shells in the p orbital, and two electrons can occupy each shell. However, electrons do not just pair up in these shells unless each sub-shell has an electron. There are 3 sub-shells in the p level, so the 2 electrons in the p level are free to be in different sub-shells.
To sum it up, Silicon has 2 unpaired electrons.