Isotopes are atoms of the same element that have different _?

Neutrons

Explanation:

Isotopes are atoms with same protons and different neutron number.  For eg: Hydrogen has 0 neutrons. But a stable isotope of hydrogen called Deuterium has 1 neutron but both still have 1 proton which makes them isotopes.

Isotopes have different mass number but same atomic number

plasma is the state of matter where the substance is ionized and has no definite shape or volume. the fact of being ionized makes the substance a good electrical conductor.

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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