Term | Definition |
An energy level | The fixed energy value that an electron in an atom may have. |
The mathematical equation relating the energy of light to its frequency | E=hf |
An orbital | A region in space within which there is a high probability of finding an electron |
An element | Is a substance that can not be split up into simpler substances by chemical means |
A triad | A group of three elements with similar chemical properties in which the atomic weight of the middle element is approximately equal to the average of the other two |
Newland's Octaves | Groups of elements arranged in order of increasing atomic weight in which the first and eighth element of each group has similar properties |
Mendeleev's Periodic Law | When elements are arranged in order of increasing atomic weight (relative atomic mass), the properties of the elements vary periodically |
The Atomic Number of an Atom | The number of protons in the nucleus of the atom |
The Modern Periodic Table | An arrangement of elements in order of increasing atomic number, with properties varying periodically |
The mass number of an element | The sum of neutrons and protons in the nucleus of an atom of that element |
Isotopes | Atoms of the same element and atomic number that have different mass numbers due to the different number of neutrons in the nucleus. |
Relative atomic mass | - The average of the mass numbers of the isotopes of the element
- as they occur naturally
- taking there abundances into account
- expressed on a scale in which the atoms of the carbon-12 isotope have a mass number of exactly 12 units. |
The Aufbau Principle | When building up the electronic configuration of an atom in its ground state, the electrons occupy the lowest available energy level |
Hund's Rule of Maximum multiplicity | When two or more orbitals of equal energy are available, the electrons occupy them singly before occupying them in pairs. |
The Pauli Exclusion Principle | no more than two electrons can occupy an orbital and they must have opposite spin. |