What is the common and IUPAC name for Oxygen?

International Union of Pure and Applied Chemistry (IUPAC) justified ways how to name organic compounds [ hydrocarbons ].

Oxygen has only a molecular name which is dioxide

Strontium has a larger atomic radius because it has more shells of electrons than magnesium does.

Mg is in Period 3 and Sr is in Period 5. Thus, Sr has two more shells of electrons than Mg.

Each shell is bigger than the one before it, so Sr has a larger atomic radius than Mg.

Both Sr and Mg have the same number of valence electrons, so they are not a factor in determining the atomic radius.

The nucleus is so small compared to the size of an electron shell that its size is not a factor in determining the atomic radius.