The Plasma State

Plasma: the negatively charged electrons (yellow) are freely streaming through the positively charged ions (blue). Image courtesy of General Atomics

Plasma is known as the fourth state of matter. The other three states are solid, liquid and gas.

Almost everything is made up of atoms (your dog, your science book, this computer...). The atom has a nucleus which has a positive charge. Electrons orbit the nucleus. The electrons (which have a negative charge) are attracted to the nucleus. Remember, opposites attract! But sometimes something comes along that sets the electrons free from orbiting the nucleus. Really hot temperatures can do this! When electrons are no longer trapped in orbits around the nucleus, we have the plasma state.

Most of the matter in the universe is found in the plasma state. That is because stars contain so much of the matter in the universe (stars are so hot that their matter can only exist in the plasma state).

Plasma: the negatively charged electrons (yellow) are freely streaming through the positively charged ions (blue). Image courtesy of General Atomics

In most cases, matter on Earth has electrons that orbit around the atom's nucleus. The negatively charged electrons are attracted to the positively charged nucleus. Remember, opposites attract! So the electrons stay in orbit around the nucleus. When temperatures get REALLY hot, the electrons can escape out of their orbit around the atom's nucleus. When the electron(s) leave, that leaves behind what scientists call a positively charged ion. This whole process is similar to a spacecraft that escapes the Earth's gravitational pull.

In summary, when electrons are no longer trapped in orbits around the nucleus, we have the plasma state. This is when a gas becomes a bunch of electrons which have escaped the pull of the nucleus and ions which are positively charged because they have lost one or more electrons.

Most of the matter in the universe is found in the plasma state. That is because stars contain so much of the matter in the universe (stars are so hot that their matter can only exist in the plasma state).

Plasma: the negatively charged electrons (yellow) are freely streaming through the positively charged ions (blue). Image courtesy of General Atomics

Plasma is known as the fourth state of matter (the first three states being solid, liquid and gas).

Matter in ordinary conditions on Earth has electrons that orbit around the atomic nucleus. The electrons are bound to the nucleus by the mutual, electrostatic attractive force. If the temperature is high enough, the electrons (at least those of the outermost orbits) acquire enough kinetic energy to escape the atom's potential (similar to a spacecraft that escapes the Earth's gravitational pull). In this situation the electrons are no longer trapped in orbits around the nucleus. This is the plasma state, where a gas becomes a collection of negatively charged electrons which have escaped the pull of the nucleus and ions which are positively charged because they have lost one or more electrons.

The majority of the matter in the universe is actually found in the plasma state. This is because stars are made up of material in the plasma state.