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Periodic Table
Term | Definition |
---|---|
Element | A substance which cannot be split into simpler substances by chemical means. |
Dobereiner's Triads | Groups of three elements of 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 eight element of each group have similar properties. |
Mendeleev's Periodic Law | When elements are arranged in order of increasing atomic weight, the properties of the elements vary periodically. |
Atomic Number | The number of protons in the nucleus of that atom. |
Modern Periodic Law | When elements are arranged in order of increasing atomic number, the properties of the elements vary periodically. |
Mass Number | The sum of the number of protons and neutrons in the nucleus of an atom of that element. |
Isotopes | Atoms of the same element, with the same atomic number, but 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 their abundance into account. Expressed on a scale in which the atoms of the Carbon 12 isotope have a mass of exactly 12 units. |
Mass Spectrometer | Vaporisation, Ionisation, Acceleration, Separation and Detection |
Aufbau Principle | States that 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 | States that when two or more orbitals of equal energy are available, the electrons occupy them singly before filling them in pairs. |
Pauli Exclusion Principle | States that no more than two electrons may occupy an orbital and they must have opposite spin. |
Atomic Radius | Half the distance between the nuclei of two atoms of the same element that are joined together by a single covalent bond. |
First Ionisation Energy | The energy required to completely remove the most loosely bound electron from a neutral gaseous atom. |