4. Inorganic Chemistry (GROUP 2 & 1)

increases due to more electron shells –> each element down group 2 has an extra shell compared to the one above it so electron is further from the nucleus

Decrease as metallic bonding weakens as atomic size increases as there is a greater distance between delocalised electrons and positive ions therefore less electrostatic attraction

decreases as distance from nucleus increases and shielding increases therefore weakening electrostatic attraction despite increased protons and nuclear charge

The reactivity increases down the group, as ionisation energy decreases As the atomic radii increases, there is more shielding as the atom gets bigger. The nuclear attraction decreases and it is easier to remove (outer) electrons and requires less energy cations form more easily

–> metal hydroxide + hydrogen —> Eg: Ba + 2H2O –> Ba(OH)2 + H2 Observations: –> fizzing, (more vigorous down group) –>the metal dissolving, (faster down group) –>the solution heating up (more down group) -> with magnesium and calcium a solid white precipitate appears (less precipitate forms down group)

–> Magnesium oxide and hydrogen - magnesium burns with a bright white flame, also produces a white solid –> Mg(s) + H2O (g) –> MgO (s) + H2(g)

–> metal oxide (solid white powder)

–> metal chloride

Oxides react readily with water to make hydroxides which disassociate to form OH- ions making the solution strongly alkaline

Forms hydroxides which make the solution more alkaline Eg: BaO + H2O –> Ba(OH)2 • MgO reacts very slowly (sparingly soluble ) and the hydroxide barely dissolves • BeO doesn’t react with water at all and hydroxide is insoluble

Called limewater Used to test for CO2 Limewater turns cloudy –> this is because calcium carbonate is produced. Ca(OH)2 (aq) + CO2 (g) –> CaCO3 (s) + H2O(l)

increases down the group - solutions become more alkaline as hydroxides become more soluble (insoluble hydroxides form white precipitate) –> Barium (bottom of group) hydroxide would easily dissolve in water. The hydroxide ions present would make the solution strongly alkaline

Bases

Neutralisation reaction forms –> salt +water

Decreases –> Barium sulphate is insoluable Solubility sinks

Compounds of group 2 that contain singly charged anion (OH- ) increase in solubility Compounds of group 2 that contain doubly charged anion (SO42- ) decrease in solubility

The use of heat to break down a reactant into more than one product

They become more thermally stable and thermally decompose less easily so more energy required to heat up

Break down into metal oxides and carbon dioxide CaCO3(s) –> CaO(s) + CO2(g)

forms metal oxides, oxygen and and nitrogen oxide 2Mg(NO3)2 → 2MgO + 4NO2 + O2 • observing a brown gas evolving and white nitrate solid melts into colourless solution and resolidifies

thermal stability for carbonates INCREASES down group 2 (becomes MORE stable) –> as the 2+ cations get bigger the charge is spread out over a larger area causing a lower charge density. So cation has a less polarising effect and distorts the carbonate ion less - the C-O bond is weakened less and so harder to break –> carbonate/ nitrate ion has a large electron cloud that is more distorted with smaller ions which causes less thermal stability –> smaller ions are found at the top of group 2

More thermally stable As you go down group 1, charge density of the ions decreases. Only Lithium has enough polarising power to cause the weakening of the C-O bond in the carbonate, and hence decompose when heated. Group 1 undergo lesser thermal decomposition so are more thermally stable. –> still produces metal oxide and carbon dioxide

SrCO3 will need to be heated to a lower temperature than BaCO3 - This is because it has a smaller ionic radius, - so it has greater polarising power, so not as much energy is needed to break the C-O bond in the carbonate ion (as it is weakened more by the Sr2+)

don’t decompose in the same way as G2 - forms a nitrite salt (NO2-) and oxygen instead 2NaNO3 → 2NaNO2 + O2 • lithium however decomposes in the same way as G2 4 LiNO3 → 2Li2O + 4NO2 + O2