S-element
In the context of chemistry, an S-element refers to a chemical element whose valence electrons (the electrons most involved in chemical bonding) are in the s atomic orbital. This means that the outermost electron shell of the element is filling its s subshell.
Elements classified as S-elements are found in Group 1 (alkali metals) and Group 2 (alkaline earth metals) of the periodic table, as well as Helium. Hydrogen also possesses a valence electron in the s orbital.
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Group 1 (Alkali Metals): These elements (Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium) have one valence electron in their s orbital (ns1 electronic configuration). They readily lose this electron to form +1 ions, making them highly reactive metals.
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Group 2 (Alkaline Earth Metals): These elements (Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium) have two valence electrons in their s orbital (ns2 electronic configuration). They readily lose these two electrons to form +2 ions, making them reactive metals, though generally less reactive than the alkali metals.
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Hydrogen (H): Hydrogen has one electron in its s orbital (1s1 electronic configuration). While it is often placed in Group 1, its properties differ significantly from the alkali metals. It can either lose its electron to form a H+ ion or gain an electron to form a H- ion.
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Helium (He): Helium has two electrons filling its s orbital (1s2 electronic configuration). This full s subshell makes it exceptionally stable and unreactive; hence, it is a noble gas.
The s orbital is spherical in shape, and its filling pattern directly influences the chemical behavior and properties of the S-elements. Their relatively simple electronic configurations contribute to their predictable reactivity and common oxidation states.