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The s- Block Element 0), Important points, , > Groups (1 & 2) belong to the s-block of the Periodic Table., , » Group | consists of : lithium, sodium, potassium, rubidium, caesium and, ffaii@ilim and collectively known as the alkali metals., , > Group 2 include : beryllium, magnesium,calcium, strontium, barium and, , , , , ey, % , a) L i: The atomic radii of alkali metals are the largest in their, , respective periods. These increase as we travel down the group., b) Large ionic radit: The ionic radii increase as we move down the group due to the, , addition of a new energy shell with each succeeding element., c) : The ionization enthalpies decrease as we move down, , the group.The ionization enthalpies of the alkali metals are the lowest due to, pelea ton decreases with the in in i6ni ii, , aml Dionlis the! maxim and the h, SUNGMGATONESEte: The MIRAGNMEMIS! exhibit SXGAHONUSMONOMLED! in their, , compounds and are strongly electropositive in character. The e'|, character increases from Li to Cs., he ases down the group., eM :: The mp and bp of alkali metals are very low, and decrease with increase in atomic number., These metals form ionic bonds. The ionic character, increases as we down the group., i) : All the alkali metals impart a charactersistic colour to the, flaiié., i) Photoelectric effect: Alkali metals (except Li) exhibits photoelectric effect., «* Chemical features of alkali metals:, , a) Reducing character: As the ionization enthalpies of the alkali metals dééreasé, down the group their reducing character or reactivity in the gaseous state, increases down the group. i.e., Li < Na < K <Rb<Cs., , b) Reaction with dihydrogen: Alkali metals react with dry hydrogen at about, 673 K to form crystalline hydrides which are ionic in nature and have high, melting points., , , , , , Heat, 2M+H, —_* 2M*H, c) Oxides and hydroxides: Alkali_metals when burnt in air form different, Compounds, for example the alkali metals on reaction with limited quantity of, oxygen form normal oxides (M20) M= Li, Na, K, Rb, Cs