Inorganic chemistry and the periodic table Flashcards
(29 cards)
What are the trends down group 2
-Forms positive ions more readily
-Forms covalent bonds less readily
-Oxides become stronger bases
-(elements become increasingly more metallic in character)
what are 3 Physical properties of group 2 metals?
-All conduct electricity
-Mp/Bp decrease down the group (except Mg)
-Hardness decreases down the group
What happens to the first ionisation energies down group 2 and why?
First ionisation energies decrease down the group as the atoms get larger and valance electrons are further away from the nucleus.
How is the increase in nuclear charge compensated for?
Increase in shielding by a larger number of inner electrons
How does reactivity change down group 2?
Reactivity increases as valance electrons are further from the nucleus and have less attraction to the nucleus making reactions more exothermic
How do group 2 metals react with oxygen (apart from Ba which forms a peroxide)
-Forms ionic oxides with the formula XO
-Reactions increase in vigour down the group
How do group 2 elements react with chlorine?
-All react vigorously to produce ionic chlorides with the formula XCl2
-All soluble in water producing hydrated ions with the formula [X(H2O)6]2+
How do group 2 elements react with water?
-React Rapidly to form an alkaline suspension of metal hydroxide and hydrogen bubbles
-(Mg burns in steam to form oxide and hydrogen)
How does group 2 oxides react with water?
-MgO reacts slowly with water to form hydroxide
-Other oxides react rapidly with water to form the hydroxide
How does group 2 oxides react with dilute acids?
Forms salt and water
How does group 2 hydroxides react with acids?
Forms salt and water
How soluble are group 2 hydroxides?
-Be(OH)2 / Mg(OH)2 are not very soluble
-Down group 2 solubility of hydroxides increases (due to increase in ionic radii)
How soluble are group 2 sulfates?
-Solubility decreases down the group
How does the thermal stability of nitrates/carbonates in group 1 and 2?
-Stability decreases in both groups; group 2 less stable than group 1 because of the 2+ cation produced making it more ‘polarising’
How do group 2 nitrates decompose?
-Decompose with heat to give metal oxide + brown fumes of nitrogen dioxide
-Lithium decomposes the same way due to it being extremely polarising
How do group 1 nitrates decompose apart from lithium?
Produce metal nitrate + oxygen
Apart from barium carbonate which is thermally stable, how do the other group 2 carbonates decompose?
Form metal oxide + carbon dioxide
Group 1 carbonates are thermally stable apart from…
lithium carbonate which forms metal oxide + CO2
How do you test the relative rates of thermal decomposition of group 1 and 2 carbonates?
-Equal amounts of carbonates in test tubes
-Bunsen burner on blue flame
-Heat test tube 1 by 1 and time for limewater to go cloudy
Group 1 flame test colours:
-Lithium - Red
-Sodium - Yellow
-Potassium - Lilac
Group 2 flame test colours:
-Calcium - Brick Red
-Strontium - Crimson Red
-Barium - Apple Green
How do colours form in a flame test?
-Heat causes vaporisation of compound and promotion of an electron to higher energy level (excitation)
-Electron falls back down to original energy level (de-excitation) and the difference in energy between orbitals dictates colour produced
How to conduct a flame test?
-Dip Platinum wire into HCl then flame then back into HCl then into substance and then flame
What are the trends in group 7:
-Atomic size increase down group
-Mp/Bp increase down group due to increasing London forces
-Electronegativity decreases down group due to reducing attraction between valance electron and nucleus
