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UNIVERSITY OF TECHNOLOGY, JAMAICA

DIVISION OF CHEMISTRY

GROUPS: DN-1, MT-1, EH-1, AS-1, BENG-1, BUILT-1, OHS

MODULE: GENERAL CHEMISTRY (CHY2021)

TUTORIAL # 2 DATE: Aug 31 - Sept 11, 2015

1. With the help of The Periodic Table, complete the table below.

Symbol Atomic # Proton # Neutron # # of Electrons Mass Number Charge

??Ar

? 40

19 20 18

31 3+

17 18 35

2. **With aid of sketches explain Rutherford and Bohrs contribution to the atomic theory. What are

the limitations of each theory?

3. Magnetic resonance imaging (MRI) is a powerful diagnostic tool used in medicine. The imagers

used in hospitals operate at a frequency of 400 MHz (1 MHz = 106 Hz). Calculate:

(a) The wavelength

(b) The energy in J per photon (energy of 1 photon)

(c) The energy in kJ per mol (energy of 1 mol of photons)

4. What is the de Broglie wavelength (in meters) of an electron for an electron of moving at 2.42 x

106 m/s? mass of electron = 9.109 x 10

-31 kg.

5. *Calculate :

(a) The energy of the n = 4 level.

(b) The energy difference from the transition that result when an electron drops from the fourth

orbit to the second in a hydrogen atom.

(c) the wavelength in metres (m) and nanometers (nm) of the spectral line.

(d) Is energy absorbed or released during this transition?

6. *An electron falls from the n = 5 energy level (i.e. ni =1) during a transition. The wavelength of

the line emitted was 1281 nm. Calculate the energy level the electron fell to (i.e. nf) to the nearest

whole number. Calculate the energy of this line.

7. Calculate the shortest wavelength of the electromagnetic radiation emitted by the hydrogen atom in

undergoing a transition from the n = 7 level. (*hint sketch the Bohr rings)

8. Based on quantum mechanics, the wave function of an atomic orbital has four quantum numbers.

(a) What is the name and symbol of each of these quantum numbers?

(b) Briefly explain which property of the atom each quantum number governs.

(c) What are the permitted values for each quantum number?

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9. Give the allowable combinations of quantum numbers for each of the following electrons:

(a) A 4s electron

(b) A 3p electron

(c) A 5f electron

(d) A 5d electron

10. *Tell which of the following combinations of quantum numbers are not allowed. Explain your

answers.

(a) n = 3, l = 0, ml = -1

(b) n = 3, l = 1, ml = 1

(c) n = 4, l = 4, ml = 0

11. What type of electron orbital (s, p, d, f) is designated by:

(a) 10 a above

(b) 10 b above

(c) n = 4, l = 3, ml =3

12. State the total capacity for electrons in:

(a) n = 4

(b) a 3s sublevel

(c) a d-sublevel

(d) a p-orbital

13. *Give the expected ground state electron configuration for the following species with and without

the use of the abbreviation of the proceeding noble gas to represent inner-shell electrons.

(a) O2- (b) Cl- (c) Ge (d) Cu2+ (e) Ta

14. *State the electronic configuration of the following transition metal ions by filling in the boxes

below. Use arrows to represent electron spin.

Ion 3d 4s

Ti2+

Fe2+

Ni2+

Cu

Co

Cr2+

15. Write electron configurations for the following:

(a) Mn in MnO2 (b) Fe in FeSO4 (c) Cu in CuCl2 (d) Co in [CoCl4]2-

(e) S in Na2S

16. **

(a) What is meant by the term effective nuclear charge?

(b) Using Slaters Rules, calculate the effective nuclear charge of an electron in the 3p orbital of

the S atom.

(c) The electronic configuration of Manganese (Mn) is 1s2.2s22p6.3s23p6.3d5.4s2. Calculate the

effective nuclear charge felt by an electron in the 3d orbital as well as an electron in the 4s

orbital.

17. Explain the general increase in ionisation energy across a period.

18. *Explain with the aid of orbital diagrams why the first ionisation energy of magnesium is greater

than that of aluminum.

19. *Explain with the aid of orbital diagrams why the first ionisation energy of sulphur is less than that

of phosphorous.

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20. Which would you expect to have the larger ionization energy, Na or Mg? Explain with orbital

diagrams.

21. What does the term isoelectronic series mean? How does it affect the ionization energy and size

of a set of isoelectronic species?

22. *Arrange the following ions in order of increasing size: Sr2+, Rb+, Se2-, As3-, Br-. Give reasons for

your order of arrangement.

23. Differentiate between electron affinity and electronegativity.

24. **The amount of energy released when an electron adds to a neutral atom to for an anion is called

the atoms electron affinity. Which would expect to have the larger electron affinity, C or N?

Explain.

25. Which atom in each of the following pairs has a larger radius?

(a) Na or K (b) V or Ta (c) V or Zn (d) Li or Ba

26. Arrange the following species in order of increasing radius. Ar, Cs, Si, Al

* Questions that are marked with an asterisk are compulsory and are must do.