CHEM1902 Main Group Chemistry
Tutorial 1 - 2015
Prof Robert J. Lancashire

1. The most accurate definition of ionization energy is ?
a) the energy required to add an electron to an atom or ion,
b) the energy required for an atom or ion to form a bond,
c) the energy required to remove a proton from the nucleus of an atom or ion,
and d) the energy required to remove an electron from an atom or ion

2. The most accurate definition of the term "electron affinity" is ?
a) the amount of energy released when an atom forms a bond,
b) the amount of energy released when an electron is lost from a neutral atom to form a cation,
c) the amount of energy required for a neutral atom to form a anion,
and d) the amount of energy released when an electron is added to a neutral atom to form an anion

3. Place the following elements in order of increasing electron affinity: Cl, Na, O, C.
a) Na, C, O, Cl,
b) Cl, O, C, Na,
c) Na, C, Cl, O,
and d) Na, O, C, Cl

4. Rank the following elements in order of increasing atomic radius: Na, B, F, Br
a) Br < Na < B < F,
b) F < B < Br < Na,
c) B < F < Na < Br,
and d) F < B < Na < Br

5. The largest atomic radius for a neutral element is expected for which of the following electron configurations?
a) [He] 2s2 2p3,
b) [Ne] 3s2 3p3,
c) [Ne] 3s2 3p5,
and d) [He] 2s2 2p5

6. Which of the following is expected to have the smallest crystal ionic radius?
a) Li+,
b) Ca2+,
c) P3+,
and d) Al3+

Short Answer Questions
1. Describe the contributions of de Chancourtois, Newlands and Mendeleev to the development of the modern periodic table.

2. Calculate the effective nuclear charge for i) an outer p electron in an oxygen atom and ii) a 3d electron in a nickel atom iii) a 4s electron in a nickel atom.

3. What is the main difference between electron affinity and electronegativity?

4. Which do you predict to have the greater electron affinity, Y or Y- ? Why?

5. Predict the type of bond that would form between elements with χ = 2.5 and 4.0? (Pauling scale)
Would this bond be more or less polar than a N-H bond? Justify your answer.

6. Account for the general increase in ionization energy across period 3.

7. Account for the dip in ionization energy that is observed from Mg to Al and from P to S.

8. How might the ionization energy, electron affinity and electronegativity affect the reactivity of the elements?

9. The molecules NH3 and NF3 have trigonal pyramidal structures, and dipole moments of 1.47 and 0.24D respectively. The values of χP(N), χP(H) and χP(F) are 3.0, 2.2 and 4.0.
Explain the variation in the observed dipole moments and show the direction of the dipoles.

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Created and maintained by Prof. Robert J. Lancashire,
The Department of Chemistry, University of the West Indies,
Mona Campus, Kingston 7, Jamaica.
Created November 2014. Links checked and/or last modified 26th January 2015.