s-BLOCK ELEMENTS

Atomic properties of Alkaline earth metals. S.No. Atomic Property Alkaline earth metals. 1. Outer electronic configuration ns^2 2. Oxidation number and valency The IP1 of these metals are much lower than IP2 and thus it appears that these metals should form univalent ion rather than divalent ions but in actual practice, all these give bivalent ion. 3. Atomic and Ionic radii The atomic and ionic radii of alkaline earth metal are smaller than corresponding alkali metals. Reason higher nuclear charge (Zeff) On moving down the group size increase, as value of n increases. BeMg>Ca>Sr>Ba IE1 of alkali metal < IE1 of alkaline earth metal. IE2 of alkali metal > IE2 of alkaline earth metal. Reason IE1 of alkaline earth metal is large due to increased nuclear charge in alkaline earth metal as compared to alkali metal but IE2 of alkali metal is large because second electron in alkali metal is to be removed from cation which has already acquired noble gas configuration. 5. Electropositivity Due to low IE they are strong electropositive but not as strong as alkali metal because of comparatively high IE. The electropositivity increases down the group. Order = Be Mg^+2 > Ca^+2 > Sr^+2 > Ba^+2 7. Electronegativity ¡] Their electronegativities are also small but are higher than that of alkali metals. ii] Electronegativity decrease from Be to Ba