1.1 ATOMIC STRUCTURE

Electronic Structure

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 represents the electronic arrangement of the outer shell of the chlorine atom (atomic number, 17)?

	3s		3p
A	¯	¯	¯
B		¯	¯	¯
C	¯
D		¯

2. Which one of the following is the electronic configuration of the bromine atom?

A 1s²2s²2p⁶3s²3p⁶3d¹⁰4s¹4p⁶

B 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁷

C 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁵

D 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶

3. To which one of the following energy levels (denoted by n) does the electron in a hydrogen atom return when the emission spectrum is in the ultraviolet region;

A n= 1

B n = 2

C n = 3

D n = 4

4. Which one of the following does not represent the electronic configuration of an atom in its ground state?

A 1s² 2s² 2p³

B 1s² 2s² 2p⁴

C 1s² 2s² 2p⁶ 3s¹

D 1s² 2s² 2p⁶ 3d¹

5. Which one of the following is the maximum number of atomic orbitals having a principal quantum number of two?

A 2

B 4

C 8

D 9

6. Which one of the following contains no unpaired electrons in the ground state?

A Be

B N

C Si

D F

7. Which one of the following is the electronic structure of a metal with a maximum oxidation state of +3?

A 1s² 2s² 2p⁶ 3s¹

B 1s² 2s² 2p⁶ 3s² 3p¹

C 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s²

D 1s² 2s² 2p⁶ 3s² 3p⁴

8. Which one of the following statements regarding electronic orbitals is correct?

A Each p-orbital can hold a maximum of six electrons.

B The 3p-orbitals have a higher energy level than the 3s-orbital.

C The three 3p-orbitals have slightly different energy levels.

D The 1s-orbital has the same size and shape as the 2s-orbital.

9. The number of electrons in the 3d orbital of the atom of atomic number 23 is

A 2

B 3

C 4

D 5

10. Which one of the following correctly represents the electronic structure of the named atom in its ground state?

A B C D
2p 2s 1s		2p 2s 1s			2p	2p 2s 1s
				2s
				1s
	Lithium		Boron Carbon Nitrogen

11. The vanadium atom (atomic number 23) in its ground state has the electronic configuration:

A 1s² 2s² 2p⁶ 3s² 3p⁶ 3d³ 4s²

B 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s³

C 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s² 4p²

D 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s² 4p¹

12. Which one of the following does not have the electronic structure

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s²4p6?

A Kr

B S^2-

C Se^2-

D Sr²⁺

13. The graph below shows the first ionisation energies for a series of elements whose atomic numbers increase in sequence. Which one could represent nitrogen?

D

1^st ionisation C

energy

B

A

atomic number

14. Which one of the following is the electronic configuration of a titanium atom?

A 1s²2s²2p⁶3s²3p⁶4s²4p²

@B 1s²2s²2p⁶3s²3p⁶3d²4s²

C 1s²2s²2p⁶3s²3p⁶3d'4s'

D 1s²2s²2p⁶3s²3p'4s'4p'

15. Which one of the following compounds contains two ions with different electronic configurations?

A CaCl₂

B MgF₂

C MgO

D NaCl

16. Which graph represents a plot of energy, E, against principal quantum number (energy level), n, for an electron in a hydrogen atom?

17. Which one of the following atoms contains no unpaired electrons in its ground state?

A Beryllium

B Boron

C Carbon

D Lithium

18. Which one of the following sub-shells does not exist?

A 2p

B 2d

C 3p

D 4d

19. Which one of the following represents the electronic structure of the chloride ion in its ground state?

20. Which one of the following represents the shape of a p-orbital?B

Section B

1. An outline of the periodic table is shown below.

(a) Indicate on it the positions of the s block, p block and d block elements. [2]

s P d

(b) Write the electronic configuration for

(i) a potassium atom

1s²2s²2p⁶3s²3p⁶4s¹

(ii) a sulphur atom

1s²2s²2p⁶3s²3p⁴ [2]

(c) Write the empirical formula for potassium sulphide indicating the charges on the ions.

K⁺₂S^2- [1]

2.

(a) Write the electronic configuration of an iron atom in the ground state

K⁺₂S^2- [1]

(b) Explain the term ground state.

K⁺₂S^2-

K⁺₂S^2-

K⁺₂S^2- [1]

3. The diagram below shows the first four energy levels in a sodium atom. Label these levels and, using arrows to represent electrons, show the electronic structure of sodium in the ground state.