Outline why the ionic radius of K⁺ is smaller than that of Cl⁻.

Outline why atomic radius decreases across period 3, sodium to chlorine.

The nitride ion and the magnesium ion are isoelectronic (they have the same electron configuration). Determine, giving a reason, which has the greater ionic radius.

Suggest why the existence of salts containing an ion with this formula could be predicted. Refer to section 6 of the data booklet.

Explain why the first ionization energy of calcium is greater than that of potassium.

Suggest two reasons why solid calcium has a greater density than solid potassium.

Calcium carbide reacts with water to form ethyne and calcium hydroxide.

CaC₂(s) + H₂O(l) → C₂H₂(g) + Ca(OH)₂(aq)

Estimate the pH of the resultant solution.

Sketch how the first ionization energies of elements vary with their atomic radius.

Sketch how the first ionization energies of elements vary with their atomic radius.

Some oxides of period 3, such as Na₂O and P₄O₁₀, react with water. A spatula measure of each oxide was added to a separate 100 cm³ flask containing distilled water and a few drops of bromothymol blue indicator.

The indicator is listed in section 22 of the data booklet.

Deduce the colour of the resulting solution and the chemical formula of the product formed after reaction with water for each oxide.

Which trends are correct across period 3 (from Na to Cl)?

I.   Atomic radius decreases
II.  Melting point increases
III. First ionization energy increases

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

Explain why an aluminium-titanium alloy is harder than pure aluminium.

In addition to magnesium oxide, magnesium forms another compound when burned in air. Suggest the formula of this compound

State an equation for the reaction of phosphorus (V) oxide, P₄O₁₀ (s), with water.

Suggest why the melting point of vanadium is higher than that of titanium.

Suggest two reasons why solid calcium has a greater density than solid potassium.

Explain why the melting points of the group 1 metals (Li → Cs) decrease down the group.

Outline why the alkali metals (group 1) have similar chemical properties.

Before its isolation, scientists predicted the existence of rhenium and some of its properties.

Suggest the basis of these predictions.

Another airbag reactant produces nitrogen gas and sodium.

Suggest, including an equation, why the products of this reactant present a safety hazard.

Which equation represents the first electron affinity of chlorine? 

A. Cl(g)+e^-→ Cl^-(g)
B. $\frac{1}{2}$Cl₂(g) + e^- → Cl^-(g) 
C. Cl⁺(g) + e^- → Cl(g) 
D. Cl(g) → Cl⁺(g) + e^-

Explain why the melting points of the group 1 metals (Li → Cs) decrease down the group whereas the melting points of the group 17 elements (F → I) increase down the group.

Write equations for the separate reactions of solid sodium oxide and solid phosphorus(V) oxide with excess water and differentiate between the solutions formed.

Sodium oxide, Na₂O:

Phosphorus(V) oxide, P₄O₁₀:

Differentiation:

Which of the following is the electron configuration of a metallic element?

A.  [Ne] 3s² 3p²

B.  [Ne] 3s² 3p⁴

C.  [Ne] 3s² 3p⁶ 3d³ 4s²

D.  [Ne] 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵

Write equations for the separate reactions of solid sodium oxide and solid phosphorus(V) oxide with excess water and differentiate between the solutions formed.

Sodium oxide, Na₂O:

Phosphorus(V) oxide, P₄O₁₀:

Differentiation:

Predict, giving two reasons, how the first ionization energy of ¹⁵N compares with that of ¹⁴N.

Suggest why it is surprising that dinitrogen monoxide dissolves in water to give a neutral solution.

Outline, in terms of their electronic structures, why the ionic radius of the sulfide ion is greater than that of the oxide ion.

Outline, in terms of their electronic structures, why the ionic radius of the sulfide ion is greater than that of the oxide ion.

Which of the following shows a general increase across period 3 from $\mathrm{Na}$ to $\mathrm{Cl}$?

A.  Ionic radius

B.  Atomic radius

C.  Ionization energy

D.  Melting point

State, giving a reason, whether the chlorine atom or the chloride ion has a larger radius.

Which oxide will dissolve in water to give the solution with the lowest pH?

A.  ${\mathrm{P}}_4{\mathrm{O}}_{10}$

B.  ${\mathrm{SiO}}_2$

C.  ${\mathrm{Al}}_2{\mathrm{O}}_3$

D.  $\mathrm{MgO}$

Outline why the chlorine atom has a smaller atomic radius than the sulfur atom.

State, giving a reason, whether the chlorine atom or the chloride ion has a larger radius.

Outline why the chlorine atom has a smaller atomic radius than the sulfur atom.

Calcium carbide reacts with water to form ethyne and calcium hydroxide.

CaC₂(s) + H₂O(l) → C₂H₂(g) + Ca(OH)₂(aq)

Estimate the pH of the resultant solution.

The nitride ion and the magnesium ion are isoelectronic (they have the same electron configuration). Determine, giving a reason, which has the greater ionic radius.