Period 5 element
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A period 5 element is an element in the fifth period (row) of the periodic table. It contains 18 elements, beginning at Rubidium and ending at Xenon.
Period 5 elements have electrons in the first five electron shells. All period 5 elements have one or more electrons in the fifth electron shell (valence electrons).
When atomic number increases by one, another electron is added.[source?] Two electrons join the 5s orbital, ten electrons join the 4d orbital, and six electrons join the 5p orbitals.