(a)(i) List the quantum number that are assigned to an electron in an atom.
(ii) What is the maximum number of electrons that can occupy the 3d orbital?
(b) An element represented as P has the following electronic configuration: 1s\(^2\)2s\(^2\)2p\(^6\)2s\(^2\)
(i) Write the electronic configuration of the ion of P.
(ii) Without identifying P, write the likely formula of its chloride.
(iii) State with reason, whether P will be a good oxidizing or reducing agent.
(c)(i) What is electron affinity?
(ii) Explain briefly why ammonia can precipitate in dative bonding.
(d)(i) If an element in Group IV loses an alpha particle, to which group would the product belong?
(ii) Two equally toxic substances X and Y which decay to non-toxic products, were absorbed through the skin. If their half-lives are 8 minutes and 2 months respectively, which of them constitutes the greater health hazard? Explain your answer
(a)(i) Quantum numbers assigned to an electron
- Principal quantum number, n (shell/energy level)
- Azimuthal (angular momentum) quantum number, l (subshell/shape)
- Magnetic quantum number, ml (orientation of orbital)
- Spin quantum number, ms (direction of electron spin, \(+\tfrac{1}{2}\) or \(-\tfrac{1}{2}\))
(ii) The 3d subshell contains 5 orbitals and each orbital holds 2 electrons, so the maximum number of electrons is 10.
(b) Taking the configuration as \(1s^2 2s^2 2p^6 3s^2\), element P has 12 electrons (a Group II metal).
(i) P loses its two outer electrons to form P2+: \(1s^2 2s^2 2p^6\).
(ii) As a divalent metal, its chloride is PCl2.
(iii) P is a good reducing agent. It has a low ionization energy and readily loses (donates) its two outer electrons to other species, thereby reducing them while itself being oxidized.
(c)(i) Electron affinity is the energy change that occurs when one mole of electrons is added to one mole of gaseous atoms of an element to form one mole of gaseous negative ions.
(ii) The nitrogen atom in ammonia carries a lone pair of electrons. This lone pair can be donated to an electron-deficient species (for example H+ to give NH4+), so ammonia readily forms a dative (coordinate) bond.
(d)(i) Loss of an alpha particle decreases the atomic number by 2, so the product moves two places to the left in the period. A Group IV element therefore gives a product in Group II.
(ii) X (half-life 8 minutes) constitutes the greater health hazard. A short half-life means X disintegrates very rapidly, so within the short time it is absorbed it emits radiation at a much higher rate (high activity) than Y, whose 2-month half-life means it decays very slowly and releases only a small amount of radiation over the same period.
(a)(i) Quantum numbers assigned to an electron
- Principal quantum number, n (shell/energy level)
- Azimuthal (angular momentum) quantum number, l (subshell/shape)
- Magnetic quantum number, ml (orientation of orbital)
- Spin quantum number, ms (direction of electron spin, \(+\tfrac{1}{2}\) or \(-\tfrac{1}{2}\))
(ii) The 3d subshell contains 5 orbitals and each orbital holds 2 electrons, so the maximum number of electrons is 10.
(b) Taking the configuration as \(1s^2 2s^2 2p^6 3s^2\), element P has 12 electrons (a Group II metal).
(i) P loses its two outer electrons to form P2+: \(1s^2 2s^2 2p^6\).
(ii) As a divalent metal, its chloride is PCl2.
(iii) P is a good reducing agent. It has a low ionization energy and readily loses (donates) its two outer electrons to other species, thereby reducing them while itself being oxidized.
(c)(i) Electron affinity is the energy change that occurs when one mole of electrons is added to one mole of gaseous atoms of an element to form one mole of gaseous negative ions.
(ii) The nitrogen atom in ammonia carries a lone pair of electrons. This lone pair can be donated to an electron-deficient species (for example H+ to give NH4+), so ammonia readily forms a dative (coordinate) bond.
(d)(i) Loss of an alpha particle decreases the atomic number by 2, so the product moves two places to the left in the period. A Group IV element therefore gives a product in Group II.
(ii) X (half-life 8 minutes) constitutes the greater health hazard. A short half-life means X disintegrates very rapidly, so within the short time it is absorbed it emits radiation at a much higher rate (high activity) than Y, whose 2-month half-life means it decays very slowly and releases only a small amount of radiation over the same period.
