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:
“Remember how often you have postponed minding your interest, and let slip those opportunities the gods have given you. It is now high time to consider what sort of world you are part of, and from what kind of governor of it you are descended; that you have a set period assigned you to act in, and unless you improve it to brighten and compose your thoughts, it will quickly run off with you, and be lost beyond recovery.”
—Marcus Aurelius Antoninus (121–180)
“Lisa Fremont: Surprise is the most important element of attack. And besides, you’re not up on your private eye literature. When they’re in trouble it’s always their girl Friday who gets them out of it.
L.B. Jeffries: Well, is she the girl who saves him from the clutches of the seductive show girls and the over passionate daughters of the rich?
Lisa Fremont: The same.
L.B. Jeffries: That’s the one, huh? But he never ends up marrying her, does he? That’s strange.”
—John Michael Hayes (b. 1919)