{"id":5981,"date":"2020-10-13T12:24:45","date_gmt":"2020-10-13T06:54:45","guid":{"rendered":"http:\/\/astan.lk\/al_virtualclassroom\/?p=5981"},"modified":"2020-10-13T12:24:56","modified_gmt":"2020-10-13T06:54:56","slug":"s-block-elements","status":"publish","type":"post","link":"https:\/\/astan.lk\/al_virtualclassroom\/s-block-elements\/","title":{"rendered":"s block elements"},"content":{"rendered":"

Reactions with water<\/strong><\/span><\/h4>\n

\u2022 All the elements of the first group react with water liberating hydrogen and become hydroxides. Example : Na reacts rapidly with water liberating hydrogen.<\/p>\n

2Na(s) + 2H2<\/sub>O(l) \u2192 2NaOH(aq) + H2<\/sub>\u00a0(g)<\/p>\n

\u2022 When a small piece of K is added into water it reacts while burning. As K reacts with water more rapidly than Na, it can be concluded that the rate of reaction with water increases down the group.<\/p>\n

\u2022 A reaction is not seen when a clean piece of Mg is added into water. When the water with Mg is warmed, it is seen to react slowly.<\/p>\n

Mg(s) + 2H2<\/sub>O(l) \u2192 Mg(OH)2<\/sub> (s) + H2<\/sub>\u00a0(g)<\/p>\n

\u2022 As the reactivity shown by Mg with water is lower compared to Na, it can be said that the metals of group II compared to metals of group I show a lower reactivity.Be does not react with water. Ca, Sr, and Ba react with water liberating hydrogen and forming the hydroxides.<\/p>\n

Ca(s) + 2H2<\/sub>O(l) \u2192 Ca(OH)2<\/sub> (aq) + H2<\/sub>\u00a0(g)<\/p>\n

\u2022 Be and Mg react with steam to form the oxides.<\/p>\n

Be(s) + H2<\/sub>O(g) \u2192 BeO(s) + H2<\/sub>\u00a0(g)<\/p>\n

Mg(s) + H2<\/sub>O(g) \u2192 MgO(s) + H2<\/sub>\u00a0(g)<\/p>\n

 <\/p>\n

Reactions with air\/O2<\/span><\/strong><\/h4>\n

There are several reactions of group I metals with air .<\/p>\n

4Na(s) + O2<\/sub>\u00a0(g) \u2192 2Na2<\/sub>O(s)<\/p>\n

2Na(s) + Excess O2<\/sub>(g) \u2192 Na2<\/sub>O2<\/sub>(s)<\/p>\n

2Na(s) + 2H2<\/sub>O(g) \u2192 2NaOH(s) + H2<\/sub>\u00a0(g)<\/p>\n

K, Rb and Cs readily react with O2<\/sub> forming superoxides.<\/p>\n

Excess K(s) + O2<\/sub> (g) \u2192\u00a0KO2<\/sub> (s)<\/p>\n

When heated in air only Li of Group I reacts with nitrogen.<\/p>\n

6Li(s) + N2<\/sub> (g) \u2192 2Li3<\/sub>N(s)<\/p>\n

When a clean piece of Mg ribbon and a small cut piece of Na are exposed to air Na tarnishes faster than Mg. Hence it is clear that the reactivity of Mg is lower than Na. \u00a0Accordingly it can be said that relative to metals of group I, the reactivity of group II metals with air is lower.<\/p>\n

Metals of the Group II when heated in air burn forming oxides and nitrides.<\/p>\n

2Mg(s) + O2<\/sub> (g) \u2192 2MgO(s)<\/p>\n

3Mg(s) + N2<\/sub> (g) \u2192 Mg3<\/sub>N2<\/sub> (s)<\/p>\n

For Be to react it should be heated to a very high temperature.<\/p>\n

 <\/p>\n

Reaction with acids <\/span><\/strong><\/h4>\n

As the metals of the group I react with acids liberating large quantity of heat, an explosion takes place. Therefore it should not be tested.<\/p>\n

2Na(s) + dil.H2<\/sub>SO4<\/sub>(aq)\u00a0\u2192 Na2<\/sub>SO4<\/sub>(aq) + H2<\/sub>(g)<\/p>\n

Group II metals reacts with dilute acids to liberate H2<\/sub>\u00a0rapidly<\/p>\n

Mg(s) +\u00a0 dil.H2<\/sub>SO4<\/sub>(aq)\u00a0\u2192 MgSO4<\/sub>(aq) + H2<\/sub>(g)<\/p>\n

Group II metals can be oxidised by concentrated acids.<\/p>\n

Mg(s) + 2 conc.H2<\/sub>SO4<\/sub>(aq)\u00a0\u2192 MgSO4<\/sub>(aq) + SO2<\/sub>(g) + H2<\/sub>O(l)<\/p>\n

Mg(s) + \u00a04 conc.HNO3<\/sub>(aq)\u00a0\u2192 Mg(NO3<\/sub>)2<\/sub>(aq) + 2NO2<\/sub>(g) + 2H2<\/sub>O(l)<\/p>\n

<\/h4>\n

Reactions with N2<\/sub><\/strong><\/span><\/h4>\n

Lithium and Group II metals form metal nitrides by reacting with N2<\/sub> gas or N2<\/sub> presents in air.<\/p>\n

6Li(s) + N2<\/sub>(g)\u00a0\u2192 2Li3<\/sub>N(s)<\/p>\n

3Mg(s) + N2<\/sub>(g)\u00a0\u2192 Mg3<\/sub>N2<\/sub>(s)<\/p>\n

 <\/p>\n

Reactions with\u00a0H2<\/sub><\/span><\/strong><\/h4>\n

s Block elements form metal hydrides by reacting with H2<\/sub>\u00a0gas.<\/p>\n

2Li(s) + H2<\/sub>(g)\u00a0\u2192 2LiH(s)<\/p>\n

2Na(s) + H2<\/sub>(g)\u00a0\u2192 2NaH(s)<\/p>\n

Mg(s) + H2<\/sub>(g)\u00a0\u2192 MgH2(s)<\/p>\n

 <\/p>\n

\u2022 Because s block elements easily remove their electrons and form cations they are considered as good reducing agents.<\/p>\n

\u2022 While atomic radius increases down the group nuclear attraction decreases. Consequently, reducing ability of the elements also increases.<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Reactions with water \u2022 All the elements of the first group react with water liberating hydrogen and become hydroxides. Example : Na reacts rapidly with water liberating hydrogen. 2Na(s) + 2H2O(l) \u2192 2NaOH(aq) + H2\u00a0(g) \u2022 When a small piece of K is added into water it reacts while burning. As K reacts with water […]<\/p>\n","protected":false},"author":842,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[14,1662],"tags":[],"class_list":["post-5981","post","type-post","status-publish","format-standard","hentry","category-chemistry","category-unit-06"],"acf":[],"yoast_head":"\ns block elements - Learning & Education Portal<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/astan.lk\/al_virtualclassroom\/s-block-elements\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"s block elements - Learning & Education Portal\" \/>\n<meta property=\"og:description\" content=\"Reactions with water \u2022 All the elements of the first group react with water liberating hydrogen and become hydroxides. Example : Na reacts rapidly with water liberating hydrogen. 2Na(s) + 2H2O(l) \u2192 2NaOH(aq) + H2\u00a0(g) \u2022 When a small piece of K is added into water it reacts while burning. 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