In what way does an isotope vary from the common form of the same element?

In other words, isotopes have the same atomic number because they are the same element but have a different atomic mass because they contain a different number of neutrons. This... Isotopes are atoms of the same element. Remember that an atom is made up of three important components: neutrons, protons, and electrons.

because there are alot of mountains

radiative zone

explanation    

radiative zone is the layer of the sun which energy is transferred away from the core by radiation. although, the core is the only part of the sun that produces an appreciable amount of heat through fusion. in fact, 99% of the energy produced by the sun takes place within 24% of the sun's radius.