Which of the following is an alkali metal?
1s22s22p63s1
1s22s22p63s23p4
1s22s22p63s23p64s2
1s22s22p63s23p64s23d5
Classification of Elements as Metals, Nonmetals and Metalloids -
The elements can be divided into three categories i.e, metals and non-metals and metalloids. Metals comprise more than 78% of all known elements and appear on the left side of the Periodic Table. Metals are usually solids at room temperature except mercury which is liquid at room temperature and even gallium and caesium also have very low melting points (303K and 302K. respectively). Metals usually have high melting and boiling points. They are good conductors of heat and electricity. They are malleable and ductile .
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Alkali metals are those metals that have last unpaired electron enter into the s-orbital. When there are two electrons in the s-orbital, then those electrons are known as alkaline earth metals.
Therefore, Option(1) is correct
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