Subfamily,periodic table of the elementsOnly containsLong-period elementVertical column of.Long period element, i.e. the outermost electron is 1 or 2,ElectronicsFilled in the secondary outer layer except s and p layerselementThat is, the elements of the 4th to 7th cycle.Subgroups are represented by Roman numerals followed by B in the periodic table of chemical elements.
In 1989, the International Union of Pure and Applied Chemistry (IPACU) proposed to cancel the main and auxiliary families and name them after 1-18 families;According to this provision, the sub families are 3-12 families.
