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Electronic Configuration of S-Block Elements.
All of the s-block elements are unified by the fact that their valence electrons (outermost electrons) are in an s orbital. The s orbital is spherical and can be occupied by a maximum of two electrons. Elements in column 1 have one electron in the s orbital, and elements in column 2 (plus helium) have two electrons in the s orbital.
Element |
Symbol |
Electronic configuration |
Li |
1s22s1 |
|
Na |
1s22s22p63s1 |
|
K |
1s22s22p63s23p64s1 |
|
Rb |
1s22s22p63s23p63d104s24p65s1 |
|
Cs |
[Xe]6s1 |
|
Fr |
[Rn]7s1 |
The s-block elements include hydrogen (H), helium (He), lithium (Li), beryllium (Be), sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), rubidium (Rb), strontium (Sr), cesium (Cs), barium (Ba), francium (Fr) and radium (Ra).
As shall be discussed later, the elements in column 1, are collectively known as the alkali metals (except hydrogen). They always lose their one valence electron to make a +1 ion. These metals are characterized by being silvery, very soft, not very dense and having low melting points. These metals react extremely vigorously with water and even oxygen to produce energy and flammable hydrogen gas. They are kept in mineral oil to reduce the chance of an unwanted reaction or worse, an unwanted explosion.
The elements in column 2, are known as the alkaline earth metals (except helium). They always lose their two valence electrons to make a +2 ion. Like the alkali metals, the alkaline earth metals are silvery, shiny and relatively soft. Some of the elements in this column also react vigorously with water and must be stored carefully.