Inorganic Flashcards
(22 cards)
What causes periodic trends in atomic radius across Period 3?
Increasing nuclear charge with no additional shielding causes a stronger attraction between the nucleus and outer electrons, reducing atomic radius across the period.
Why do melting points vary across Period 3?
Giant metallic structures (Na–Al) show increasing melting point due to higher charge density. Silicon (Si) has a giant covalent structure (very high m.p.). P, S, Cl are molecular — weaker van der Waals = lower m.p. S₈ > P₄ > Cl₂.
Why does ionisation energy increase across a period?
More protons = greater nuclear attraction. Same shielding, atomic radius decreases. Exceptions: Al (3p electron) < Mg (3s electron), S < P due to electron repulsion in paired 3p orbitals.
What is the trend in reactivity down Group 2?
Reactivity increases as atomic radius increases and first and second ionisation energies decrease — outer electrons are lost more easily.
Write the ionic equation for the reaction between magnesium and water.
Mg(s) + 2H₂O(l) → Mg(OH)₂(aq) + H₂(g)
What is the solubility trend of Group 2 hydroxides and sulfates?
Hydroxides: solubility increases down the group (Mg(OH)₂ sparingly soluble; Ba(OH)₂ very soluble).
Sulfates: solubility decreases down the group (BaSO₄ insoluble — used in medical imaging).
What’s the test for sulfate ions using Group 2 compounds?
Add HCl (removes CO₃²⁻) then BaCl₂ → white precipitate of BaSO₄ confirms SO₄²⁻ presence.
What is the trend in electronegativity in Group 7?
Decreases down the group: more shells = increased shielding = weaker attraction for bonding pair of electrons.
Describe the trend in boiling point down Group 7.
Increases due to stronger van der Waals forces as molecular mass increases.
What are the results of halogen displacement reactions in solution?
Cl₂ displaces Br⁻ (orange) and I⁻ (brown), Br₂ displaces I⁻ (brown), I₂ displaces none.
Why is chlorine added to water
Forms HClO, a weak bleach that kills bacteria. Reaction: Cl₂ + H₂O ⇌ HCl + HClO
What are the ethical issues of chlorinating water?
Kills pathogens (advantage), but can form toxic chlorinated hydrocarbons (disadvantage). Risk-benefit analysis favours its use.
Define oxidation and reduction in terms of electron transfer.
Oxidation = loss of electrons. Reduction = gain of electrons.
What is a disproportionation reaction? Give an example.
A redox reaction in which the same species is both oxidised and reduced. Example: Cl₂ + H₂O → HCl + HClO
Define a transition metal.
A d-block element that forms at least one ion with an incomplete d-subshell.
Why is Sc not a transition metal?
Sc³⁺ has an empty 3d subshell — no variable oxidation state or coloured ions.
Explain why transition metals form coloured compounds.
Ligand field causes d-orbital splitting; electrons absorb specific visible light to promote excitation. Remaining wavelengths = observed colour.
What is a ligand and what is coordination number?
Ligand: species that donates lone pair to metal ion. Coordination number: number of coordinate bonds to metal ion.
What are common complex shapes for coordination numbers 4 and 6?
4: tetrahedral (e.g. [CuCl₄]²⁻) or square planar (e.g. [Ni(CN)₄]²⁻),
6: octahedral (e.g. [Fe(H₂O)₆]³⁺)
What is the chelate effect?
Multidentate ligands (e.g. EDTA⁴⁻) form more stable complexes due to increase in entropy when replacing monodentate ligands.
What is the test for ammonium ions?
Add NaOH and warm → ammonia gas evolved (turns damp red litmus paper blue).
How do you test for halide ions?
Add dilute nitric acid, then silver nitrate:
Cl⁻ = white ppt, Br⁻ = cream ppt, I⁻ = yellow ppt. Confirm with NH₃:
Cl⁻ dissolves in dilute NH₃, Br⁻ only in conc NH₃, I⁻ insoluble.
