Deuterium is an of hydrogen because it has one proton and one neutron in its whereas hydrogen only has one proton.
a. element, nucleus
b. element, valence shell
c. isotope, nucleus
d. isotope, valence shell

There is one s orbital, and there are three p orbitals, five d orbitals, and seven f orbitals. thus, the answer is b. do not confuse the number of orbitals in a subshell with the number of electrons the subshell can hold. each orbital can hold two electrons, so the capacity of an nf subshell is 14 electrons.

It's a