A period 1 element is one of the chemical elements in the first row (or period) of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The first period contains fewer elements than any other row in the table, with only two: hydrogen and helium. This situation can be explained by modern theories of atomic structure. In a quantum mechanical description of atomic structure, this period corresponds to the filling of the 1s orbital. Period 1 elements obey the duet rule in that they need two electrons to complete their valence shell. The maximum number of electrons that these elements can accommodate is two, both in the 1s orbital. Therefore, period 1 can have only two elements.
Read more about Period 1 Element: Periodic Trends, Position of Period 1 Elements in The Periodic Table, Elements
Famous quotes containing the words period and/or element:
“Intellectual life is international. Only a period of discouragement, an age that has given up on itself, that wants to “preserve,” that has been driven onto the defensive, can be intellectually nationalist. Such a period is essentially “conservative.” A person who has progress in his heart is international.”
—Robert Musil (1880–1942)
“Only the rare expands our minds, only as we shudder in the face of a new force do our feelings increase. Therefore the extraordinary is always the measure of all greatness. And the creative element always remains the value superior to all others and the mind superior to our minds.”
—Stefan Zweig (18811942)