The electron is one of the elementary particles that makes up the atom along with the positively charged atomic nucleus. The electrons carry a negative charge. The mass of the electron, when compared to proton and neutron is very less. The mass is 1/1836 of a proton. As electrons have a very less mass, and due to the uncertainty principle, electrons are impossible to locate precisely. Due to this, when you try to confine an electron close to the atomic nucleus, their momentum increases. So when the positive nucleus electrostatically attracts the electron towards it, the high momentum of the electron repels the force and settles at certain configurations as orbitals where the probability of finding the electron is high.
Frequently Asked Questionsedit
Why don't the electrons crash into the nucleus?edit
The electrons do not occupy a definite position around a nucleus. Due to its fundamental nature bound by quantum mechanics, they exist in orbitals around the nucleus. As described in the explanation section, the more the electron is brought near the nucleus, the more the momentum of it will be. The increased kinetic energy of the electron makes it whiz around the nucleus in a way that it exists in a state of superposition, like a cloud. The shape and size of this cloud, where the probability of finding the electron is determined by the electrostatic attraction of the nucleus. The stable shell is where this attraction and the momentum stabilises and finds a balance. Therefore, electrons cannot crash into the nucleus.