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CHAPTER 5
The Periodic Law
Section 1: History of the Periodic Table
Periodic law: The physical and chemical properties of the elements are periodic
functions of their atomic numbers.
Reworded Periodic law: When the elements are arranged in order of increasing
atomic number, elements with similar properties appear at regular intervals.
Periodic table: Arrangement of the elements in order of their atomic numbers so
that elements with similar properties fall in the same column, or group
Lanthanides: 14 elements with atomic numbers from 58 to 71
Actinides: 14 elements with atomic numbers from 90 to 103
Section 2: Electron Configuration and the Periodic Table
Alkali metals: Group 1 of the Periodic Table
Alkaline-earth metals: Group 2
Transition elements: d-block elements with typical metallic properties
Main-Group elements: p-block elements and s-block elements
Halogens: Group 17
Section 3: Electron Configuration and Periodic Properties
Atomic radius: ½ the distance between the nuclei of identical atoms that are
bonded together
Ion: atom or group of bonded atoms that has a positive or negative charge
Ionization energy: energy required to remove one electron from a neutral atom of
an element
Electron Affinity: energy change that occurs when an electron is acquired by a
neutral atom
Cation: positive ion
Anion: negative ion
Valence electrons: electrons available to be lost, gained, or shared in the
formation of chemical compounds
Electronegativity: measure of the ability of an atom in a chemical compound to
attract electrons
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