Topic 4: Inorganic Chemistry & The Periodic Table 1️⃣

Decrease

Despite the increase in nuclear charge the combined effect of the following factors results in a decrease in ionisation energy down the group: - As each quantum shell is added energy of the outermost electrons increases - As the number of filled shells increases their force of repulsion on the electron being removed increases

General increase in reactivity down the groups explained by the decrease in energy required to remove the 2 electrons from each atom of the element (ionisation energy)

Reactions are more vigorous down the group due to sum of ionisation energies decreasing down the group For all of the reactions, the element needs to be heated for the reaction to start although even without, there is a slow reaction if the element is exposed to air (surface coating of oxide which prevents further reaction)

• As each electron is removed there is less repulsion between electrons and so they will be drawn slightly closer to the nucleus. • As the distance of each electron from the nucleus decreases slightly the nuclear attraction increases • More energy is required to remove each successive electron

Under oil

Group 2 elements combine with chlorine when heated in the gas.(form ionic bonds) Reactions become more vigorous down the group (trend harder to see than reaction with oxygen) as sum of ionisation energies decreases down the group

Reaction of magnesium with water is very slow and does not proceed completely Calcium, strontium and barium react with increasing vigour which can be seen by increasing effervescence due to sum of ionisation energies decreasing down the group

Precipitate of calcium hydroxide forms as calcium is only slightly soluble in water

Rapidly forms magnesium oxide (white solid) and hydrogen gas

Safety reason : prevents the escape of a highly flammable gas into the lab

2M(s) + O2(g) —-> 2MO(s)

M(s) + Cl2(g) —-> MCl2(s)

M(s) + 2H2O(l) —-> M(OH)2(aq) + H2(g) With calcium: Ca(s) + 2H2O(l) —-> Ca(OH)2(s) + H2(g)

Group 2 oxides are classed as basic oxides, which means that can react with water to form alkalis Observation : Solids react to form a colourless solutions

Solubility increases down the group pH value increases down the group

Bubbled through limewater. (Ca(OH)2) Cloudy precipitate indicates positive test CO2 + Ca(OH)2 ——> CaCO3 + H2O

Milk of magnesium is essentially a suspension of magnesium hydroxide in water It is sold as an indigestion remedy (acts as an antacid) It neutralises some of the excess HCl in the stomach Mg(OH)2 + 2HCl —-> MgCl2 + 2H2O

Although hydroxide ions attack human tissue, the very low solubility of magnesium hydroxide means that the conc of OH- ions in the medicine is very low = no risk to health 

React to form salt + water Described as neutralisation reactions White solid reacts to form colourless solution

Neutralises excess acidity in the soil and increases yield of crops

Decreases down the group

Adding a solution containing barium ions (usually barium chloride or barium nitrate) & dilute hydrochloric/nitric acid Any sulfate ions in a solution react with the added barium ions to form the white precipitate of barium sulfate

There are other anions that could also form a white precipitate with barium ions, especially carbonate ions, so in the test there must be H+ ions present to prevent them from forming