Chemistry

• The nucleus is a positively charged region at the center of an atom
• The nucleus consists of subatomic particles called neutrons and protons
• The nucleus has electrons revolving around it
• A specific type of atom has its own atomic number, which gives the number of protons
• Mass numbers are calculated by the number of protons plus the number of neutrons
• Isotopes are atoms with the same numbers of protons but different number of neutrons
• A specific electron in an atom can be described by a wave equation
• The solution to a wave equation is called a wave function, or orbitals
• An orbital describes the volume of a space where an electron is most likely to occupy
• Orbitals in an atom are organized into different layers around the nucleus and have successively larger size and energy
• Orbitals within a given shell are oriented in space mutually along perpendicular directions
• The Aufbau principle states that the lowest energy orbitals fill up first in order
• Electrons spins around an axis, this spin can have two directions, up and down. Only two electrons can occupy an orbital, and they must have opposite spins. A statement known as the Pauli-exclusion principle
• Every orbital must be singly occupied before it is doubly occupied. A statement called Hund's rule