ANS_EX_5 - Swieter p1 of 11 CHM1040 Answer to Exercise Set...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
X:\~Natsci\ADJUNCT\bhaskar\pdf\1041\ANS_EX#5.DOC CHM1040 Answer to Exercise Set 5 QUESTIONS ABOUT IONIC SUBSTANCES 1. a) Formation of a positive ion requires the removal of one or more electrons from the neutral parent atom. The remaining electrons experience a decrease in the degree of electron-electron repulsion. Consequently, the attractions between the nucleus and the valence electrons now exceed the repulsions between the valence electrons which cause the valence electrons to be drawn inward toward the nucleus and thus decreasing the radius of the ion relative to the parent atom. b) Formation of a negative ion requires the addition of one or more electrons to the neutral parent atom. The additional electron(s) cause an increase in the degree of electron-electron repulsions. Consequently, the repulsions between the valence electrons now exceed the attractions between the nucleus and the valence electrons. This causes the valence electrons to be pushed outward away from the nucleus and thus increasing the radius of the ion relative to the parent atom. 2. We should expect the hydrogen ion, H + , to be the smallest of all chemical species, since it consists of a lone proton. The hydride ion, H - , should be larger than the He atom. Although He and H - both have two electrons (1s 2 ), the H - has only one proton to interact with the two electrons while He has two protons. 3. Recall that the elements in the s and p blocks tend to form ions with the noble gas configurations. a) Mg is in group IIA. These elements have relatively low ionization energies and unfavorable electron affinities and thus form cations. Mg can achieve a noble gas configuration (NGC) by losing two electrons. Therefore, Mg is expected to form a +2 ion (Mg +2 ). b) K is in group IA. Like Mg, K is expected to form a cation but it will achieve an NGC by loss of one electron and therefore K is expected to form a +1 ion (K + ). c) Al is in group IIIA. Like Mg and K, Al is expected to form a cation but must lose three electrons to achieve NGC. Therefore Al is expected to form Al +3 ions. d) P is in group VA. These elements have relatively high ionization energies and favorable electron affinities and therefore form anions. P can achieve an NGC by gaining three electrons. Therefore, P is expected to form an anion with a -3 charge (P -3 ). e) I is in group VIIA. Like P, I is expected to form an anion but will achieve an NGC by gaining one electron and thus I is expected to form a -1 ion (I - ). f) Te is in group VIA. Like P and I, Te is expected to form an anion but with a -2 charge (Te -2 ). 4. Ionic compounds form only when electrical neutrality is maintained. Therefore the cations and anions must combine in such number that the compound is electrically neutral (i.e., carry no charge). a) Ca is expected to form Ca
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 11

ANS_EX_5 - Swieter p1 of 11 CHM1040 Answer to Exercise Set...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online