We know that a neutral atom of bromine (br) is larger than a neutral atom of magnesium (mg) because a.) group numbers tells us how many electrons orbitals surround a nucleus, bromine is in group 7a while magnesium is in group 2a b.)period numbers tells us how many electron orbitals surround a nucleus, bromine is in period 4 while magnesium is in period 3 c.)atoms with many electrons are always larger than atoms with fewer electrons, a neutral atom of bromine has 35 electrons while neutral atom of magnesium has only 12. d.) bromine and magnesium has very different physical and chemical properties.

Option (C) is the correct answer.

Explanation:

Bromine is a group 7A element with atomic number 35. Whereas magnesium is a group 2A element with atomic number 12.

This means that a neutral atom of bromine has more number of electrons as compared to a neutral atom of magnesium. Hence, size of a bromine atom will definitely be larger than the size of a magnesium atom.

Thus, we can conclude that we know that a neutral atom of bromine (Br) is larger than a neutral atom of magnesium (Mg) because atoms with many electrons are always larger than atoms with fewer electrons, a neutral atom of bromine has 35 electrons while neutral atom of magnesium has only 12.