The Periodic Table: Families and Periods. In the periodic table of elements, there are seven horizontal rows of elements called periods. The vertical columns of elements are called groups, or families. read more
Period (periodic table) In the periodic table of the elements, each numbered row is a period. A period in the periodic table is one of the horizontal rows, all of whose elements have the same number of electron shells. Going across a period, each element has one more proton and is less metallic than its predecessor. read more
In the periodic table of elements, there are seven horizontal rows of elements called periods. The vertical columns of elements are called groups, or families. (See also The Periodic Table: Metals, Nonmetals, and Metalloids.) In each period (horizontal row), the atomic numbers increase from left to right. read more
Periodic table. The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configurations, and recurring chemical properties. This ordering shows periodic trends, such as elements with similar behaviour in the same column. read more