First, find moles of oxygen gas: (3.01 x10^23 molec.)/(6.02 x10^23) =0.5mol O2
Second, multiply moles by the standard molar volume of a gas at STP:(0.5mol)(22.4L) = 11.2L O2
It defines the element. If you change the protons, you change the type of element. A proton is positively charged and is most of the mass of the atom, next to the neutron. Neutrons have a very very very slightly higher mass.
The ion composition of Magnesium is 12,10, 2+.
Magnesium is a chemical element with symbol Mg and an atomic number 12, it has 12 protons, and 12 electrons with a chemical configuration of 2:8:2. It requires to loose two electrons to form a stable configuration forming a cation (positively charged ion) with a charge of +2 and a configuration of 2:8 ( 12 protons and 10 electrons).