(a)(i) List three properties of elements which increase generally across a period in the Periodic Table,
(ii) Give two differences between a chemical reaction and a nuclear reaction.
(b) Use the information provided in the table below to answer Questions (i) - (vii).
| Atom of Element |
P |
Q |
R |
S |
T |
| Mass Number |
16 |
40 |
35 |
18 |
20 |
| Atomic Number |
8 |
20 |
17 |
8 |
10 |
Which of the atoms in the table above:
(i) are isotopes of the same element?;
(ii) contains 18 neutrons?;
(iii) is chemically unreactive?;
(iv) readily forms an ion with two positive charges?
(v) attain an octet structure by accepting one electron?;
(vi) forms ionic bond with R?;
(vii) belongs to the s-block in the Periodic Table?
(c) Describe in outline how each of the following conversions can be carried out in the laboratory. Write appropriate equations for the reactions involved in each case
(i) \( \mathrm{CuCO_3} \) to \( \mathrm{Cu} \)
(ii) \( \mathrm{MgO} \) to \( \mathrm{MgSO_4} \).
(a)(i) Three properties that increase generally across a period: ionisation energy, electronegativity, and electron affinity (non-metallic character also increases).
(a)(ii) Two differences between a chemical reaction and a nuclear reaction:
| Chemical reaction | Nuclear reaction |
|---|
| Involves only the outer (valence) electrons; the nucleus is unchanged. | Involves the nucleus itself (protons and neutrons change). |
| Relatively small energy changes; no new element is formed. | Enormous energy changes; new elements are formed (transmutation). |
(b) The atoms
| Element | P | Q | R | S | T |
|---|
| Mass number | 16 | 40 | 35 | 18 | 20 |
| Atomic number | 8 | 20 | 17 | 8 | 10 |
| Neutrons (mass - atomic no.) | 8 | 20 | 18 | 10 | 10 |
- (i) Isotopes of the same element: P and S (both have atomic number 8).
- (ii) Contains 18 neutrons: R (35 - 17 = 18).
- (iii) Chemically unreactive: T (atomic number 10, a noble gas with a stable octet).
- (iv) Readily forms an ion with two positive charges: Q (atomic number 20, group II, forms Q\(^{2+}\)).
- (v) Attains an octet by accepting one electron: R (atomic number 17, seven outer electrons, gains one).
- (vi) Forms an ionic bond with R: Q (a metal that donates its two outer electrons to the non-metal R).
- (vii) Belongs to the s-block: Q (its outer electrons occupy the 4s sub-shell).
(c)(i) CuCO\(_3\) to Cu
Heat the copper(II) trioxocarbonate(IV) strongly to give the oxide, then reduce the oxide by passing hydrogen (or heating with carbon) over it:
\[ \text{CuCO}_3 \xrightarrow{\text{heat}} \text{CuO} + \text{CO}_2 \]
\[ \text{CuO} + \text{H}_2 \xrightarrow{\text{heat}} \text{Cu} + \text{H}_2\text{O} \]
(c)(ii) MgO to MgSO\(_4\)
Add the magnesium oxide (a base) to warm dilute tetraoxosulphate(VI) acid until no more dissolves; filter off excess oxide, then evaporate and crystallise the filtrate:
\[ \text{MgO} + \text{H}_2\text{SO}_4 \rightarrow \text{MgSO}_4 + \text{H}_2\text{O} \]
(a)(i) Three properties that increase generally across a period: ionisation energy, electronegativity, and electron affinity (non-metallic character also increases).
(a)(ii) Two differences between a chemical reaction and a nuclear reaction:
| Chemical reaction | Nuclear reaction |
|---|
| Involves only the outer (valence) electrons; the nucleus is unchanged. | Involves the nucleus itself (protons and neutrons change). |
| Relatively small energy changes; no new element is formed. | Enormous energy changes; new elements are formed (transmutation). |
(b) The atoms
| Element | P | Q | R | S | T |
|---|
| Mass number | 16 | 40 | 35 | 18 | 20 |
| Atomic number | 8 | 20 | 17 | 8 | 10 |
| Neutrons (mass - atomic no.) | 8 | 20 | 18 | 10 | 10 |
- (i) Isotopes of the same element: P and S (both have atomic number 8).
- (ii) Contains 18 neutrons: R (35 - 17 = 18).
- (iii) Chemically unreactive: T (atomic number 10, a noble gas with a stable octet).
- (iv) Readily forms an ion with two positive charges: Q (atomic number 20, group II, forms Q\(^{2+}\)).
- (v) Attains an octet by accepting one electron: R (atomic number 17, seven outer electrons, gains one).
- (vi) Forms an ionic bond with R: Q (a metal that donates its two outer electrons to the non-metal R).
- (vii) Belongs to the s-block: Q (its outer electrons occupy the 4s sub-shell).
(c)(i) CuCO\(_3\) to Cu
Heat the copper(II) trioxocarbonate(IV) strongly to give the oxide, then reduce the oxide by passing hydrogen (or heating with carbon) over it:
\[ \text{CuCO}_3 \xrightarrow{\text{heat}} \text{CuO} + \text{CO}_2 \]
\[ \text{CuO} + \text{H}_2 \xrightarrow{\text{heat}} \text{Cu} + \text{H}_2\text{O} \]
(c)(ii) MgO to MgSO\(_4\)
Add the magnesium oxide (a base) to warm dilute tetraoxosulphate(VI) acid until no more dissolves; filter off excess oxide, then evaporate and crystallise the filtrate:
\[ \text{MgO} + \text{H}_2\text{SO}_4 \rightarrow \text{MgSO}_4 + \text{H}_2\text{O} \]
