Inorganic Chem

Describe and explain the trend in atomic radius of elements from Na to Ar

Proton number increase → Nuclear charge increase

Electrons added - all in same energy level

No significant increase in shielding - electrons not added to inner shells

Increased nuclear charge pulls OE close to nucleus → smaller AR

Describe and explain trend in first ionisation energy of element Na to Ar

Na to Ar, proton number increases

Increases + charge in nucleus → stronger electrostatic attraction between nucleus and OE

More energy to remove

Electron added to same energy level

Distance from nucleus stays constant

No inner shells added → shielding stays same

More energy needed to remove → Higher first IE

What anomalies are there in the first ionisation energy of element Na to Ar

Mg → Al

Al OE in P subshell, Al in S

P higher than S subshell

More energy to remove

P → S

S has one pair of repelling electrons in a box

Repulsion makes it easier to remove

Describe and explain the trend in MP and BP from elements Na to Ar

Increase Na → Al

• Metallic bonding strength increase - more delocalised electrons - higher + charge on metals - stronger attraction between ion and electron

• Mp increase

Sharp drop at Si

• Giant covalent structure - each Si atom bonded to 4 others in strong 3D lattice - need lots of energy to break lots of strong COV bonds

• Highest MP in P3

Decrease from P → Ar

• Simple molecular substances - held by weak VDW forces - P and S larger molecules so more VDW so stronger - need more energy to break

Describe and explain trends in atomic radius of G2 elements

AR increase from Mg → Ba

• Each element has an extra electron shell

• Increases distance of OE from nucleus

• Although nuclear charge increases, increased shielding and greater distance outweigh it

• OE less attracted

• Atom becomes larger

Describe and explain trends in first ionisation energy of G2 elements

IE decreases from Mg → Ba

• OE further from nucleus - more shells - weaker nuclear attraction

• More shielding from inner shells

• Less energy needed to remove OE

Describe and explain trends in MP and BP in G2 elements

Generally decreases

• All G2 elements have metallic bonding

• Larger atoms means metallic bond weakens - + ions larger - attraction between them and delocalised electron weaker

• Less energy needed to break the metallic bonds

Ca is anomaly

Trend of G2 elements reacting with water

Reactivity increases down group

Reaction of Mg with water

Mg (s) + 2H₂O (l) → Mg(OH)₂ (aq) + H₂ (g)

• Slowly with cold water

• Form few bubbles

Mg (s) + H₂O (g) → MgO (s) + H₂ (g)

• React faster with steam

Reaction of Ca with water

Ca (s) + 2H₂O (l) → Ca(OH)₂ (aq) + H₂ (g)

• Reacts readily with cold water'

• Fizzes

• Cloudy solution due to slightly insoluble Ca(OH)₂ (aq)

Reaction of Sr with water

Sr (s) + 2H₂O (l) → Sr(OH)₂ (aq) + H₂ (g)

• Vigorously reacts

• Slightly alkaline solution - Sr(OH)₂ (aq) soluble in water

Reaction of Ba and water

Ba (s) + 2H₂O (l) → Ba(OH)₂ (aq) + H₂ (g)

• React vigorously in cold water

Solubility trend down G2 hydroxides

Increase

• Mg(OH)₂: Slightly soluble (suspension or insoluble white precipitate in water)

• Ca(OH)₂: Moderately soluble (cloudy in water)

• Sr(OH)₂: Soluble (forms a clear solution)

• Ba(OH)₂: Highly soluble (forms a clear solution)

Hydroxide solubility of Mg

MgCl2 (aq) + NaOH (aq) → 2NaCl (aq) + Mg(OH)2

• 2NaCl - no flame colour

• Mg(OH)2 - white precipitate

Hydroxide solubility of Ca

CaCl2 (aq) + NaOH (aq) → 2NaCl (aq) + Ca(OH)2 (s)

• Ca(OH)2 - orange/red flame - sparingly dissolved

Hydroxide solubility of Sr

SrCl2 (aq) + NaOH (aq) → 2NaCl + Sr(OH)2 (s)

• Sr(OH)2 - partially soluble

Hydroxide solubility of Ba

BaCl2 (aq) + NaOH (aq) → 2NaCl + Ba(OH)2 (aq)

• Ba(OH)2 - colourless

Solubility trend down G2 sulphates

Decrease

• Magnesium sulphate (MgSO₄): Very soluble

• Calcium sulphate (CaSO₄): Slightly soluble

• Strontium sulphate (SrSO₄): Insoluble

• Barium sulphate (BaSO₄): Insoluble

Sulphate solubility of G2: Mg

MgCl2 (aq) + H2SO4 → 2HCl + MgSO4 (aq)

• MgSO4 - colourless

Sulphate solubility of G2: Ca

CaCl2 (aq) + H2SO4 → 2HCl + CaSO4

• CaSO4 - partially soluble

Sulphate solubility of G2: Sr

SrCl2 (aq) + H2SO4 → 2HCl + SrSO4

• SrSO4 - sparingly soluble

Sulphate solubility of G2: Ba

BaCl2 (aq) + H2SO4 → 2HCl + BaSO4 (aq)

• BaSO4 - white precipitate

Uses of Mg

Extract Titanium from an ore rutile (TiO2)

TiO2 + 2C + 2Cl2 → TiCl4 + 2CO

TiCl4 + 2Mg → Ti + 2MgCl2

Uses of BaSO4

Barium metal

Give to patient who needs an x-ray

Doesn’t let x-ray past it

Safe to use, insoluble - ions not absorbed in blood - no free ions

Uses of Mg(OH)2

Milk of magnesia

Neutralise stomach acid

Uses of Ca(OH)2

Slaked Lime

Sprayed on fields by farmers - partially soluble - neutralise acidity of soil - get more crops

Uses of CaCO3

Calcium Carbonate

Limestone

Uses of CaO

In flue gas desulphurisation

CaO + SO2 → CaSO3

In rain, acid rain passes through bed of CaO - makes CaSO3

• Used to make clay

• Gas that comes out has no SO2

State and explain the trend in BP of G7 in terms of their structure and bonding

BP increases as you go down

Halogens are diatomic molecules - simple covalent between atoms

Held together by weak VDW forces

• As you go down electron number increase → atom size increase → more VDW → more energy needed to break

State and explain trend in electronegativity down G7

Decreases as you go down

Atomic radius increases - more electron shells - OE further from nucleus

Shielding increase - more inner shells

Nuclear attraction decrease - even though proton number increases - shielding and distance outweigh this

State and explain the trend in oxidising ability of the elements down G7 using ideas about electron transfer

Decreases as you go down

Atomic radius increases - OE further from nucleus

Shielding increases - more inner shell block attraction of OE and nucleus

Attraction for electron decreases - harder for halogen atom to attract and gain an electron

State and explain the trend in reducing ability of the halide ions down G7 using ideas about electron transfer

Increases as you go down

Ionic radius increases - OE further from nucleus

Shielding increases - more inner shells - weaker nuclear attraction to OE

Easier to lose electron - more readily donates electrons

Recall the use of acidified silver nitrate solution to identify and distinguish between halide ions and the associated observations. Explain why the silver nitrate solution is acidified.

1) Add dilute nitric acid to the sample

2) Add silver nitrate solution (AgNO3)

Chloride - white precipitate

Bromide - cream precipitate

Iodide - yellow precipitate

Silver nitrate acidified - removes carbonate/hydroxide ions - could also form precipitates with Ag+

• Unwanted precipitates would interfere with the test - give false positives

Recall trend in solubility of silver halides in ammonia

Decreases down group

AgCl - soluble in dilute NH3

AgBr - soluble in concentrated NH3

AgI - insoluble in ammonia

Recall disproportionation reaction of chlorine with water to form chloride ions and chlorate (I) ions

Cl2​+H2​O→HCl+HClO

Recall the reaction of chlorine with water to form chloride ions and oxygen

2Cl2​+2H2​O→4HCl+O2​

Recall the use of chlorine in water treatment and appreciate that society that assesses the advantages and disadvantages when deciding if chemicals should be added to water supplies

Kills harmful bacteria and pathogens

Cl2​+H2​O→HCl+HClO

• Chloric acid (HClO) ionises to form chlorate ions (ClO-)

• These kill bacteria

Appreciate that the benefits to health of water treatment by chlorine outweigh its toxic effects

Chlorine in water treatment - decline in waterborne diseases - saving lives

Toxicity risks are acknowledged - safe chlorination levels are controlled

Benefits—ensuring safe, clean drinking water—are considered to outweigh the risks for public health

Recall the disproportionation reaction of chlorine with cold, dilute, aqueous NaOH and uses of the solution formed

Cl2​+2NaOH (aq)→NaCl (aq)+NaClO (aq)+H2​O (l)