1. Electronic Structure
Noadswood Science, 2016

2. Monday, May 21, 2018
Electronic Structure
To be able to represent the electron structure of atoms

3. Precise Learning
The electrons in an atom occupy the lowest available energy levels (innermost available shells). The electronic structure of an atom can be represented by numbers or by a diagram. For example, the electronic structure of sodium is 2,8,1 or
showing two electrons in the lowest energy level, eight in the second energy level and one in the third energy level (students should be able to represent the electronic structures of the first twenty elements of the periodic table in both forms)
Students may answer questions in terms of either energy levels or shells.

4. Nucleus containing protons and neutrons
Atomic Structure
Atoms consist of a nucleus (containing protons and neutrons) which are orbited by electrons, within specific shells…
Electrons
Nucleus containing protons and neutrons

5. Electron Shells
Electrons which orbit the nucleus of an atom occupy specific shells – the follow some specific rules: -
Electrons always occupy shells (energy levels)
The lowest energy levels are always filled up first
Only a certain number of electrons are allowed in each shell (1st shell = 2; 2nd shell = 8; 3rd shell = 8)
In most atoms the outer shell is not full, making them want to react

6. Electron Shells Electrons of an atom are arranged in shells… x x x x x
The first shell only has 2 electrons at most
The next two shells can contain up to 8 electrons in each x x x x x x x x x x x x
The number of electrons in the outer shell affects the properties of the atom (i.e. it’s reactivity) x x
Each shell must be filled up before electrons can be added to the next shell x x

7. Electron Shells – Potassium (K)39 K x x x 19
19 protons
20 neutrons
19 electrons x x x
Potassium (K) has 19 electrons – these are arranged as follows…
1st shell = 2
2nd shell = 8
3rd shell = 8
4th shell = 1 x x x x x x x x x x x x x

8. Electron Shells – Potassium (K)
Potassium has 1 outer electron (found in group I) – meaning it is very reactive!

9. H B O Na Cl Ca Electron Shells
Using the information note the number of protons, neutrons and electrons of the following elements, and draw their electron shell structures… 1 H 11 B 16 O 1 5 8 23 Na 35 Cl 40 Ca 11 17 20

10. H Electron Structure – 1 Hydrogen: - 1 1 1 proton 0 neutronsx 1 H 1

11. B Electron Structure – 2,3 Boron: - 11 5 5 protons 6 neutronsx x x x x 11 B 5

12. O Electron Structure – 2,6 Oxygen: - 16 8 8 protons 8 neutrons

13. Na Electron Structure – 2,8,1 Sodium: - 23 11 11 protons 12 neutronsx x x x x x x x 23 Na x x x 11

14. Cl Electron Structure – 2,8,7 Chlorine: - 35 17 17 protons 18 neutronsx x x x x x x x x x x x x 35 Cl x x x x 17

15. Ca Electron Structure – 2,8,8,2 Calcium: - 40 20 x 20 protons
20 neutrons
20 electrons x x x x x x x x x x x x x x x 40 Ca x x x x 20 x

16. Electrons Underlying Chemistry
Electrons occupying shells around the nucleus is the ‘cause’ of all underlying chemistry
When elements react their atoms join with other atoms forming compounds – this involves giving, taking, and sharing of electrons
What link is there between the electron structure and the elements position within the periodic table?

17. Electron Structure
There is a link between an atom's electronic structure and its position in the periodic table – an atom's electronic structure can be worked out from its place in the periodic table…

18. Electron Structure Atoms in group I have 1 electron in the out shell
Atoms in group II have 2 electrons in the outer shell
Atoms in group III have 3 electrons in the outer shell etc…
Atoms in group VIII have a full outer shell

19. Building A Nucleus

20. Electron Structure

21. Remember Electrons are arranged in different shells around the nucleus
The innermost shell - or lowest energy level - is filled first
Each succeeding shell can only hold a certain number of electrons before it becomes full - the innermost shell can hold a maximum of two electrons, the second shell a maximum of eight, and so on...
Energy Level (Shell)
Maximum No. Electrons
First 2
Second 8
Third
Fourth 18

22. Lithium
For example, work out the atomic structure of Lithium...

23. Lithium
Lithium - 2nd period so it has 2 circles drawn around it and in group 1 so it has 1 electrons in the outer shell...

24. Lithium
Lithium (Li) - 2,1 (three electrons (2 in shell 1 and 1 in shell 2))

25. Summary
Electrons which orbit the nucleus of an atom occupy specific shells – the follow some specific rules: -
Electrons always occupy shells (energy levels)
The lowest energy levels are always filled up first
Only a certain number of electrons are allowed in each shell (1st shell = 2; 2nd shell = 8; 3rd shell = 8; 4th shell = 18)
In most atoms the outer shell is not full, making them want to react

26. Atomic Structure Anagrams

27. Practice Questions What is another name for an electron shell?
What is the maximum number of electrons that can go in the first electron shell?
What is the maximum number of electrons that can go in the second electron shell?
What is the maximum number of electrons that can go in the third electron shell?
Which shell fills with electrons first?

28. Answers An energy level 2 electrons 8 electrons
The one closest to the nucleus (lowest energy level)