Question | Answer |
an element | an element is a substance that cannot be split up into simpler substances by chemical means |
a triad | a triad is a group of elements with similar chemical properties in which the atomic weight of the middle element is approximately equal to the average of the other two |
Newlands' Octaves | Newlands' Octaves are groups of elements arranged in order of increasing atomic weight in which the first and the eighth element of each group have similar properties |
Mendeleev's Periodic Law | Mendeleev's Periodic Law: when elements are arranged in order of increasing atomic weight(relavtive atomic mass) the properties of the elements vary periodically |
atomic number | the atomic number of an atom is the number of protons in the nucleus of that atom |
the modern periodic table | the modern periodic table is an arrangment of elements in order of increasing atomic number |
when elements are arranged in order of increasing atomic number | the properties of the elements vary periodically |
the mass number of an element | the mass number of an elementis the sum of the number of protons and neutrons in the nucleus of an atom of that element |
isotopes | isotopes are atoms of the same element (with 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 that element
as they occur naturally
taking their abundancies into account
expressed on a scale in which the atoms of the carbon-12 isotope have a mass of exactly 12 units |
the aufbau principle | the 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. |
Hunds rule of maximum multiplicity | Hunds rule of maximum multiplicity ststes that when two or more orbitals of equal energy are available, the electrons occupy them singly before filling them in pairs |
the pauli exclusion principle | the pauli exclusion principle states that no more than two electrons may occupy an orbital and they must have opposite spin. |