What does x represent for this transmutation?

 49be +  24he→x +  01n

 513b

 612c

 613c 

 25he

Which terms are used to identify pure substances

What are some natural measures of time

Acertain atom has 22 protons and 19 electrons. this atom loses an electron. the net charge on the atom is now 4+1+01-4-. if this same atom with 22 protons and 19 electrons were to gain 3 electrons, the net charge on the atom would be 3+2+02-3-.