5. ATOMIC AND ELECTRONIC STRUCTURE (PART 3)

Question 1

1. Provide names for the following labels?

Answer 1

1. Element
2. Total Electrons
3. Box Orbital Diagram
4. Electron Configuration
5. Number of Electrons

Question 2

2. What does Hund’s Rule state?

Answer 2

• we should maximise the number of unpaired spin-up electrons

Question 3

3. What happens when we pair up electrons in the same orbital?

Answer 3

• we force them to share the same space
• both electrons are negative
• both electrons have the same charge
• these two electrons repel each other
• the increase in repulsion causes an increase in the energy of the atom
• the atom is less stable

NB: this is why we keep electrons unpaired

Question 4

4. How and why do we keep electrons unpaired?

Answer 4

• we keep them unpaired by placing them in adjacent orbitals
• they have a lower repulsive energy when they are unpaired
• there is no electromagnetic resistance
• the orbital is much more stable

Question 5

5. Do we place the unpaired electrons as spin-up or spin-down electrons?
   WHY?

Answer 5

• spin up electrons
• they have a lower energy as they are working in the same direction of the magnetic field
• the atom is more stable

Question 6

6. Which of these Carbon atoms is the most stable?

Answer 6

• Option D

Question 7

7. What does a violation of Hund’s Rule lead to?

Answer 7

• it leads to excited electronic states
• these have a higher energy than the lowest ground state

Question 8

8. Provide names for the following labels?

Answer 8

1. Ground state
   (the lowest energy state)
2. Excited State
   (higher energy)
3. Excited State
   (higher energy)
4. Excited State
   (higher energy)

Question 9

9. What is Pauli’s Exclusion Principle?

Answer 9

• no two electrons in a given atom can have the same set of 4 quantum numbers
• at least one of the quantum numbers has to be different
• the quantum numbers are: n, L, mL, mS

Question 10

10. Which of these are the two best examples of Pauli’s Exclusion Principle?

Answer 10

B and C

Question 11

11. What type of Electronic Configuration is this?

Answer 11

Full Electronic Configurations

Question 12

12. What type of Electronic Configuration this is?

Answer 12

Noble Gas Electron Configurations

Question 13

13. What type of Electronic Configuration is this?

Answer 13

Condensed Electronic Configurations

Question 14

14. Provide names for the following labels?

Answer 14

1. Full Electronic Configuration
2. Condensed Electronic Configuration
3. Box Orbital Diagram

Question 15

15. What kind of Electronic Configuration is this?

Answer 15

• it is an Anomalous Electronic Configuration

Question 16

16. What happens in an Anomalous Electron Configuration?

Answer 16

• one electron is promoted from the 4s to the 3d sub shell
• this is to achieve a d5 (half full d sub shell) or a d 10 (full d sub shell) configuration

Question 17

17. Why is a d5 or a d10 sub shell desirable?

Answer 17

• they have a special degree of stability

Question 18

18. Can you change a d3 or a d8 sub shell to a d5 or a d10 sub shell?

Answer 18

• NO
• you can only change a d4 or a d9 sub shell

Question 19

19. Elements in which other groups will have anomalous electronic configurations?

Answer 19

• Group 6
• Group 11

Question 20

20. Electrons from which orbital are likely to leave first when there is a transfer of electrons (ionic/covalent bonding)?

Answer 20

• electrons from the s orbital
• this is the outermost electron configuration
• these electrons are found in the outermost shell of the atom

Question 21

21. What is another name for the electrons found in the outermost shell, and what do they do?

Answer 21

• they are called Valence electrons
• they are exchanged between other atoms

Question 22

22. What is shielding?

Answer 22

• it is when we cannot see the nucleus of the atom as something is blocking us from seeing it
• an electron cloud or a higher density of electrons in the shells is what causes this shielding

Question 23

23. What is the value and the symbol of the valence electrons of Group 1 (Alkali Metal) elements?

Answer 23

• s1
• they have an extra electron to freely give away to reach an octet (most stable state)

Question 24

24. What is the value and the symbol of the valence electrons of Group 7 (halogens) elements?

Answer 24

• p6
• they are seeking an extra electron to reach an octet (most stable state)

Question 25

25. What is atomic radius?

Answer 25

- the distance from the centre of the atom to its circumference - it can also be seen to be the size of the atom

Question 26

26. How does the atomic radius react with regard to groups and periods?

Answer 26

- it increases as we move down the group - it decreases as we move right along the period

Question 27

27. Why does the atomic radius increase as we move down the group?

Answer 27

- this is due to the addition of extra shells as we move down the group - the extra shells have an increasing Principle Quantum Number (n) - this makes them larger in size

Question 28

28. Why does the atomic radius decrease as you go along the period?

Answer 28

- electrons are being placed in the same shell as we move along the period - these shells are still at the same distance from the nucleus as they were before the addition of the other electrons - the nuclear charge increases by one unit each time we move to the right - the increasing nuclear (positive) charge attracts the electrons in the shells - this pulls the shells closer to the nucleus - this decreases the size of the atom

Question 29

29. What is the Ionisation energy?

Answer 29

- the energy required to remove one electron from a neutral atom - it is the energy we have to use up in order to remove the electron from the attractive force of the nucleus

Question 30

30. Which law is proven through the fact that electrons are attracted to the nucleus?

Answer 30

- Coulomb's law

Question 31

31. What is the formula to work out the ionisation energy?

Answer 31

Question 32

32. What does Q1 represent?

Answer 32

- the effective nuclear charge (the number of protons-the number of intermediate electrons)

Question 33

33. What are intermediate electrons?

Answer 33

- electrons that shield the nucleus - this ensures that the valence electron does not feel the full positive charge

Question 34

34. What does Q2 represent?

Answer 34

- it is equal to the value of one electron (Q2 = -1)

Question 35

35. What happens the atomic number increases?

Answer 35

- Q1 increases - the energy of attraction to the electron also increases - this makes it much more difficult to separate an electron from it's attractive force to the nucleus

Question 36

36. What does R represent?

Answer 36

- the distance of the electron from the nucleus

Question 37

37. What happens when R increases?

Answer 37

- the energy of attraction decreases

Question 38

38. What happens when the number of atomic shells increases?

Answer 38

- R increases - energy of attraction decreases

Question 39

39. What has exactly the opposite trend than the atomic radius?

Answer 39

- the ionisation energy

Question 40

40. Read through the summary. Does everything make sense?

Answer 40

- yes