1.1 ATOMIC STRUCTURE

Ionisation Energy

Section A

For each of the questions only one of the lettered responses (A-D) is correct.

Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet.

1. Which one of the following has the largest first ionisation energy?

A carbon

B fluorine

C neon

D nitrogen

2. The second ionisation energy for calcium is represented by the equation

A Ca(s) Ca²⁺ (g) + 2e^-

B Ca(g) Ca ²⁺ (g) + 2e^-

C Ca⁺(s) Ca²⁺ (g) + e^-

D Ca⁺(g) Ca²⁺(g) + e^-

4. The first six ionisation energies of an element Y are as follows:

786, 1580, 3230, 4360, 16 000, 20 000 kJ mol^-1

Which one of the following statements is consistent with these data.

A Y is in Group I of the Periodic Table.

B The outer electronic configuration of an atom of Y is ns²np²

C Y forms a chloride with the molecular formula YCl

D The chemistry of Y and its compounds is similar to that of aluminium and its compounds.

5. In which one of the following series of elements is there the smallest variation in the value of the first ionisation energy?

A Li to F

B F to I

C K to Br

D Sc to Zn

6. Which one of the following processes requires the largest amount of energy?

A He (g) He⁺(g) + e^-

B Ne (g) Ne⁺(g) + e^-

C Na (g) Na⁺ (g) + e^-

D Ca (g) Ca⁺ (g) + e^-

7. Which one of the following statements is correct?

A The first ionisation energy of oxygen is greater than that of nitrogen.

B The second ionisation energy is always greater than the first ionisation energy for a chosen element.

C The first ionisation energy of an element. M. is the energy associated with the process M(s) M⁺ (aq) + e^-

D Ionisation energy increases with increasing atomic number.

8. Which one of the following sets of ionisation energies corresponds to an element in Group II?

1st 2nd 3rd 4th 5th

A 580 1800 2700 11600 14800

B 1520 2700 3900 5800 7200

C 790 1600 3200 4400 16100

D 740 1500 7700 10500 13600

9. What frequency of radiation in Hz is required to ionise helium?

He He⁺ + e^- ΔH = +2370 kJ mol^-1

A 1.69 x 10^-16

B 9.48 x 10^-10

C 1.05 x 10⁹

D 5.93 x 10

10.The first ionisation energy for carbon is greater than it is for sodium. One of the factors responsible is that the

A nuclear charge on carbon is greater

B shielding provided by the inner quantum shells of sodium is greater

C number of electrons in the outer quantum shell of carbon is greater than in sodium

D outer quantum shell is further from the nucleus in carbon atoms than in sodium atoms

11. The ground state electronic configurations of five elements are shown below. For which element would you expect the value of the first ionisation energy to be the greatest?

1s 2s 2p

A B
A B
C D
C D

12.An element has successive ionisation energies of 99, 1800, 14800 and 21000 kJ mol^-1. To which group of the Periodic Table does the element belong?

A I

B II

C III

D IV

13. The first four ionisation energies of an element Z are 738, 1451, 7733 and 10541 kJ mol^-1. Which one of the following ions is most likely to be formed when Z reacts with fluorine?

A Z⁺

B Z²⁺

C Z³⁺

D Z⁴⁺

14. The graph represents the variation in the first ionisation energy with atomic number.

The elements indicated by letters P, Q, R and S are all

A alkali metals

B halogens

C noble gases

D transition metals

15. The graph below shows the first six successive ionisation energies, I_e, of an element. In which Group of the Periodic Table is the element found?

A Group 11

B Group IV

C Group V

D Group VI

SECTION B

Answer all questions in the spaces provided

1. Here is some information concerning element X, of atomic number 31. In its natural state, it consists of a mixture of two isotopes X_A and X_B.

Isotope	Isotopic mass	Percentage abundance
X_A	69.0	60.2
X_B	71.0	39.8

Its first four ionisation energies are 580, 2000, 3000 and 6200 kJ mol^-1.

(a) Calculate the value for the relative atomic mass of X correct to three significant figures.

[3]

(b) Write down the electronic configuration of element X in its ground state.

X = 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p¹ [1]

Group III [1]

(d) Explain why:

(i) The difference between the first and second ionisation energies is greater than that between the second and third ionisation energies.

[2]

(ii) The difference between the third and fourth ionisation energies is much larger than that between the other successive energies.

[2]

2. The first five ionisation energies, in kJ mol^-1, of two elements Q and R are shown below:

	First	Second	Third	Fourth	Fifth
Q	600	1800	3000	12000	15700
R	520	5500	7100	9500	13500

(a)

(i) In which groups of the Periodic Table would you expect to find elements Q and R? explain your reasoning for element Q.

[3]

(ii) Explain why the element directly below R in the Periodic Table would be expected to have a smaller ionisation energy than R.

[3]

(b) Using element R define the term second ionisation energy and write an appropriate equation.

[3]

3.

(a) The first ionisation energies for a sequence of elements are shown in the graph:

(i) State whether the first ionisation energy of potassium would be more or less than that of sodium. Explain your choice.

[2]

(ii) Explain the shape of the graph.

[2]

(b) The successive ionisation energies of two elements A and B are listed below:

units are kJ mol-1.

1st 2nd 3rd 4th 5th 6th

A 420 3100 4301 5891 7999 9512

B 589 1098 4811 6498 8080 10482

(i) Which group in the periodic table does element A belong to?

Explain briefly your reasoning.

[2]

(ii) What is the likely charge on an ion of element B? Explain your reasoning.

[2]

4. The graph below shows the first ionisation energies of the elements

from hydrogen to sodium.

(a) What is meant by the term first ionisation energy?

[2]

(b) (i) Explain why there is an overall rise in first ionisation energy

in going from lithium to neon.

[2]

(ii) Explain why the first ionisation energy falls markedly from helium to lithium.

[2]

(iii) Explain why there is a fall in the first ionisation energy from nitrogen to oxygen.

[2]

(iv) Explain why the first ionisation energy of sodium is less than that of lithium.