What is an isotope?
a.
a form of an element with a different number of electrons
c.
a form of an atom with a different amount of orbitals
b.
a form of an atom with a different number of protons
d.
a form of an atom with a different number of neutrons

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

the transfer of heat by electromagnetic radiation is called thermal radiation . it is usually carried out by electromagnetic waves in an energy range just below the visible spectrum, which is the infrared range.

so the answer would be radiation.

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