Electron
Definition
The tiny negatively charged particle that occupies the space around the nucleus. Electrons are the actors in chemical bonding and reactions.
Symbol: ·
Technical definition
An electron is a negatively charged subatomic particle (charge -1e, mass about 5.486 x 10^-4 u) occupying quantized orbitals around the nucleus. The electron arrangement, called the electron configuration, determines an element's chemical properties, bonding, and reactivity.
Example
Sodium loses one electron to become Na+, while chlorine gains one electron to become Cl-. That electron transfer is the basis of table salt.
Common confusion
Electrons have real mass, just very little of it, about 1/1836 of a proton's mass. They are not pure energy or clouds of nothing.