3.1.2

• If something can dissolve it has pH 7
• The longer a bond or attraction the weaker it is
• Silicon dioxide makes up sand
• Group 2 are called alkaline earth metals
• Group 2 have high melting and boiling points, low density, form white compounds and colourless solutions
• Group 2 + oxygen -> group 2 oxide
• Group 2 + water -> group 2 hydroxide + hydrogen
• Group 2 + steam -> group 2 oxide + hydrogen
• Group 2 + acid -> salt + hydrogen
• Disproportionation : an element is reduced and oxidised in the same reaction
• Reactivity increases down group 2 as there are more electrons, more shielding, less attraction, so less energy required to remove an electron, lowering the ionisation energy, causing an electron to be lost easier causing increased reactivity
• Group 2 is less reactive than group 1 as group 2 contains 2 electrons in its outer shell requiring more energy than to just remove 1
• Group 2 oxide + water -> metal hydroxide
• down group 2 pH increases
• Non metal oxide + water -> acidic
• Metal oxide + water -> alkaline
• group 2 metal hydroxides get more soluble as you go down the group releasing more OH- ions increasing alkalinity
• Group 2 oxide + acid -> salt + water
• Group 2 hydroxide + acid -> salt + water
• Group 2 carbonate + acid -> salt + water + carbon dioxide
• Ca(OH)2 : also known as lime is used by farmers to neutralise acidic soil
• Mg(OH)2 : neutralises excess stomach acid, antacid
• CaCO3 : also known as limestone, reacts with acids, can remove sulfur dioxide gas
• ionisation energy decreases down group 2 as electron shielding and atomic radius increases counteracting the increase in nuclear charge, the 2s subshell is full so the electrons repel each other requiring even less energy