(a) What is the shape of (i) p - orbital; (ii) a molecule of methane; (iii) a molecule of carbon (IV) oxide?
(b) Consider the following elements: Ne, S, CI, 0, Fe, Mg. State which of them
(i) exhibit(s) allotropy;
(ii) form(s) coloured ions;
(iii) is/are malleable;
(iv) consist(s) of molecules that are far apart at room temperature;
(v) form(s) hydrides by sharing electrons with hydrogen;
(vi) has/have complete outermost shell.
(c)(i) List three applications of radioactivity in different fields.
(ii) Explain clearly the difference between the following reactions involving electron loss from lead.
\(^{211} pb\) \(\to\) \(^{ 211}Bi\) + \(^0_{-1}\); Pb \(\to\) pb\(^{3+}\) _ 2e\(^-\)
(iii) Give one advantage and one disadvantage of nuclear power generation over the use of fossil fuels.
(a) Shapes
- (i) A p-orbital is dumb-bell (double-lobed) shaped.
- (ii) A molecule of methane, \(CH_4\), is tetrahedral (bond angle \(109.5^\circ\)).
- (iii) A molecule of carbon(IV) oxide, \(CO_2\), is linear (bond angle \(180^\circ\)).
(b) From \(Ne, S, Cl, O, Fe, Mg\):
- (i) Exhibit allotropy: S and O (sulphur: rhombic and monoclinic; oxygen: \(O_2\) and \(O_3\)).
- (ii) Form coloured ions: Fe (a transition metal).
- (iii) Malleable: Fe and Mg (metals).
- (iv) Molecules far apart at room temperature (gases): Ne, Cl and O.
- (v) Form hydrides by sharing electrons (covalent hydrides): S, Cl and O.
- (vi) Has a complete outermost shell: Ne (a noble gas).
(c)(i) Three applications of radioactivity: medicine (radiotherapy for cancer and radioactive tracers), agriculture (inducing mutations and preserving food), and archaeology/geology (radiocarbon dating). Detecting leaks and generating nuclear power are also acceptable.
(c)(ii) Difference between the two changes
\(^{211}Pb \to\ ^{211}Bi + \ ^{0}_{-1}e\) is a nuclear (radioactive) change: a beta particle (electron) is emitted from the nucleus, so a proton is formed and a new element (bismuth) results.
\(Pb \to Pb^{2+} + 2e^-\) is an ordinary chemical (ionisation) change: electrons are lost from the outermost shell, forming an ion of the same element (lead), with no change to the nucleus.
(c)(iii) Advantage of nuclear power over fossil fuels: a very small mass of fuel yields an enormous amount of energy and it produces no carbon(IV) oxide or other combustion gases. Disadvantage: it produces dangerous radioactive waste that is difficult to dispose of and there is a risk of harmful radiation leakage.
(a) Shapes
- (i) A p-orbital is dumb-bell (double-lobed) shaped.
- (ii) A molecule of methane, \(CH_4\), is tetrahedral (bond angle \(109.5^\circ\)).
- (iii) A molecule of carbon(IV) oxide, \(CO_2\), is linear (bond angle \(180^\circ\)).
(b) From \(Ne, S, Cl, O, Fe, Mg\):
- (i) Exhibit allotropy: S and O (sulphur: rhombic and monoclinic; oxygen: \(O_2\) and \(O_3\)).
- (ii) Form coloured ions: Fe (a transition metal).
- (iii) Malleable: Fe and Mg (metals).
- (iv) Molecules far apart at room temperature (gases): Ne, Cl and O.
- (v) Form hydrides by sharing electrons (covalent hydrides): S, Cl and O.
- (vi) Has a complete outermost shell: Ne (a noble gas).
(c)(i) Three applications of radioactivity: medicine (radiotherapy for cancer and radioactive tracers), agriculture (inducing mutations and preserving food), and archaeology/geology (radiocarbon dating). Detecting leaks and generating nuclear power are also acceptable.
(c)(ii) Difference between the two changes
\(^{211}Pb \to\ ^{211}Bi + \ ^{0}_{-1}e\) is a nuclear (radioactive) change: a beta particle (electron) is emitted from the nucleus, so a proton is formed and a new element (bismuth) results.
\(Pb \to Pb^{2+} + 2e^-\) is an ordinary chemical (ionisation) change: electrons are lost from the outermost shell, forming an ion of the same element (lead), with no change to the nucleus.
(c)(iii) Advantage of nuclear power over fossil fuels: a very small mass of fuel yields an enormous amount of energy and it produces no carbon(IV) oxide or other combustion gases. Disadvantage: it produces dangerous radioactive waste that is difficult to dispose of and there is a risk of harmful radiation leakage.
