A radical is a reactive intermediate with a single electron, formed by of a covalent bond.

D)can be increased in a closed system

Hello,#agreed with joseph002.i got my source also from  source: hope this

13 protons and 14 neutrons.  this also means that the amount of electrons also is 13 because electrons have the same amount as protons..the atomic number means the amount of protons (which effectively tells you the electrons) the atomic mass, tells you the amount of protons and neutrons in the nucleus.hope this .