Chapter 9 - Group 2, the alkaline earth metals

chapter 9 - Group 2, the alkaline earth metals

electron arrangement - 2 e-s in an outer s-orbital the s-orbital becomes further away from the nucleus going down the group due to inc. shielding and weaker nuclear pullatom size - inc. as you go down bc an extra layer of electrons each time you go downmelting points - high melting points, typical of giant metallic strength of metallic bonds dec. as delocalised sea of electrons gets further away from the positive nuclei, the bonds become easier to break, so melting requires less energy: melting points dec. MAGNESIUM DOES NOT FIT THE TRENDionisation energies - (losing two outer electrons for group 2) dec. down the group because it takes less energy to remove the electrons as they become further and further away from the positive nucleus and they are more shielded by more inner shells of electrons

the chemical reactions they are all oxidised during reactions (oxidation state 0 to 2), meaning they are reducing agents of the other reactantmetals get MORE reactive as you go down the group bc the atomic radius inc. and the amount of shielding inc. so the nucleus has a weaker pull on outer electrons and can therefore lose them more easily, making them more reactivemilk of magnesia - used to help indigestion by neutralising excess stomach acid Mg(OH)2

the solubilities of the hydroxides and sulfateshydroxides - inc. in solubilityall hydroxides are white solidsMg(OH)2 - milk of magnesia almost insoluable, more of a suspension in waterCa(OH)2 - sparingly soluable and the sol. is used as lime waterSr(OH)2 - more soluableBa(OH)2 - dissolves to produce a strong alkali sol.sulfates - dec. in solubilityBaSO4 is virtually insol. - taken by mouth to outline gut in X-rays bc it is insol. it can't damage the body (it is highly toxic)can also be used as a test for sulfate ions1.add an acid to remove carbonate ions as CO2 and stop the chance of side reactions happening2. add BaCl and if sulfate ions are present, they will react w/ Ba to produce BaSo4 which will form a white pptnb: sulphuric acid must not be used as the acid bc that will add sulfate ions and will defeat the point of the test