![]() They follow the sequence Na Mg 2+ > Ca 2+ > Sr 2+ > Ba 2+ Physical Properties Alkali metals are strong reducing agents.Hydroxide and dihydrogen gas are formed in reaction with water:.Apple green is due to the presence of barium. The alkaline earth metal salts produce the following flame colours: Calcium is responsible for the brick red colour. They provide colour to an oxidising flame.They generally have a low density which increases as we go down the group.Alkali metals are light, soft, and silvery-white in colour.This is due to the greater size of the atom from which the valence shell electron can be easily removed. The ionisation energy decreases as we go down from Li to Cs.There is an increase in the radii of the atoms from Li to Cs (moving down the group).Since they easily dissolve in water and form highly alkaline soluble hydroxides, they are called alkali metals.These elements have the electronic configuration ns 1, where n signifies the valence shell.The following is the general electronic configuration:Īlkaline earth metals: ns 2 Group 1 of s-Block Elementsġs 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 5s 1 In this way, elements having their last electron in the s-subshell are called s-block elements. The last or the outermost electron may be present in the s, p, d, or f subshells. The electrons in an atom occupy various sub-orbitals of the available energy levels in the order of the increasing energy. The s-block elements that have only one electron in their s-orbital are called group one or alkali metals, whereas the s-block elements that have two electrons filling their s-orbital are called group two or alkaline earth metals.
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