(a) The electronic configuration of five elements represented by the letters P, Q, R, S and T are indicated below. P - 1s\(_2\)2s\(_2\)2p\(_2\) Q 1s\(_2\)2s\(_2\)2p\(_4\) R 1s\(_2\)2s\(_2\)2p\(_6\) S - 1s\(_2\)2s\(_2\)2p\(_6\)3s\(_2\) T - 1s\(_2\)2s\(_2\)2p\(_6\)3s\(_2\)3p\(_5\)
without identifying the elements, state which of them (i) belongs to group VI in the periodic table; (ii) is strongly metallic in character; (iii) readily ionizes by gaining one electron; (iv) contains two unpaired electrons in the ground state atom (v) readily loses two electrons during chemical bonding (vi) Does not paricipates in chemical reactions? (vii) is an s-block element.
(b)(i) Copy and complete the table below as appropriate
Particle
Number of Protons
Number of Electrons
Number of Neutrons
\(^1_1H\)
1
1
\(^{27}_{13}\)Al\(^{3+}\)
\(^{16}_{8}O^{2+}\)
8
(ii) Give the reason why atomic radius increases down a group in the periodic table but decreases from left to right in a period.
(c)(i) What is meant by the half-life of a radioactive element? (ii) The nuclide \(^{210}_{84}PO\) loses an alpha 4° particle to form lead. Write an equation for the reaction.
(d) State the type of chemical bonding which accounts for each of the following observations: (i) Chlorine exists as discrete molecules (ii) Sodium chloride dissolves readily in water; (iii) CuSO\(_{4(aq)}\) forms a deep blue complex ion with excess NH\(_{3(aq)}\)
Explanation
(a)(i) Q belongs to group VI in the periodic table. (ii) S is strongly metallic in character (iii) T readily ionizes by gaining one electrons (iv) P and Q contain two unpaired electrons in the ground state atom; (v) S readily loses two electrons during chemical bonding (vi) R does not participate readily in chemical reactions (vii) S is an s-block element.
(b)
Particle
Number of Protons
Number of Electrons
Number of Neutrons
\(^1_1H\)
1
1
0
\(^{27}_{13}\)Al\(^{3+}\)
13
10
14
\(^{16}_{8}O^{2+}\)
8
10
8
(ii) Atomic radius-increases down a group in the periodic table but decreases from left to right across a period, because as atomic number/ number of electrons increases down a group, number of shells increases, hence atomic size increases. Across a period the number of electrons and protons also increases but there is no increase in the number of shells/ the electrons are added to the same shell. The resultant effect is that the electrons in the orbit experience a greater pull towards the nucleus/ effective nuclear charge increases resulting in decrease in size. (c)(i) The half-life of a radioactive element is the time taken for half of the total number of atoms in a given sample of the element to decay. (ii) \(^{210}_{84}PO\) \(\to\) \(^{206}_{82}PO\) + \(^{4}_{2}He\)
(d) The type of chemical bonding that accounts for the following observations: (i) Chlorine exists as discrete molecules-covalent (ii) Sodium chlorine dissolves readily in water-ionic/electrovalent (iii) CuSO\(_{4(aq)}\) forms a deep blue complexion with excess NH\(_3\) –coordinate covalent/dative.
