Question

how the electrons in an atom are arranged in different shells/orbits?

Answer 1

Electrons are tiny subatomic particles with a negative charge that orbit in shells around the nucleus of an atom. Each shell can be considered an energy level, and each energy level must be full of electrons prior to an electron moving to a higher energy shell.The number of electrons in an atom is the same as the number of protons. These electrons are arranged in shells or 'energy levels' around the nucleus. The arrangement of electronsdetermines the chemical properties of an element.