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Chemistry Ch. 4
Term | Definition |
---|---|
Element | a substance that cannot be split up into simpler substances by chemical means |
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 the eight element of each group have 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 |
atomic number | the number of protons in the nucleus of an atom |
Modern periodic table | an arrangement of elements in order of increasing atomic number |
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 an element |
isotopes | atoms of the same element (ie. they have the same 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 their abundances into account -expressed on a scale in which atoms of the carbon-12 isotope have a mass of exactly 12 units. |
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 filling them in pairs |
Pauli Exclusion Principle | no more than two electrons may occupy an orbital and they must have opposite spin |