1. Electron Shells Friday, 21 September 2018
L.O: To know that electrons are found in shells/energy levels and draw a diagram of the structure of an atom based on it’s atomic number.

2. How are electrons arranged in atoms?
Electrons always occupy shells (sometimes called energy levels).
The electron shells with the lowest energy are always filled first — these are the ones closest to the nucleus.
Only a certain number of electrons are allowed in each shell.
Atoms are much happier when they have full electron shells — like the noble gases in Group 0. In most atoms the outer shell is not full and this makes the atom want to react to fill it.

3. Electronic Structure is…
…how the electrons are arranged in an atom of that element.
Electronic Structure is…

4. Electronic Structure
You need to know the electronic structures for the first 20 elements (things get a bit more complicated after that). But they're not hard to work out. You just need to follow these steps:
Find the number of electrons in an atom of the element (using the periodic table).
Draw the first electron shell and add up to two electrons to it.
Draw the second electron shell and add up to eight electrons to it.
Draw the third electron shell and add up to eight electrons.
Draw the fourth electron shell and add up to two electrons.
As soon as you've added enough electrons, stop.

5. Q: Draw the electronic structure of Potassium (K)
For example…

6. Step 1 -
Find the number of electrons in an atom of the element (using the periodic table).
19 ELECTRONS

7. Step 2 -
Draw the first electron shell and add up to two electrons to it.

8. Step 3 -
Draw the second electron shell and add up to eight electrons to it.

9. Step 4 -
Draw the third electron shell and add up to eight electrons to it.

10. Step 5 -
Draw the fourth electron shell and add up to 2 electrons to it.

11. Writing Electronic Structure
Drawing an atom is one way of showing its electronic structure, but you can also write out the electronic structure using numbers.
For example, you can show the electronic structure of nitrogen by drawing it, like this…
But you can also show it by writing it out, like this…

12. Questions Q1 Fact Recall Application
What is another name for an electron shell?
How many electrons can go in the first electron shell?
How many electrons can go in the second electron shell?
How many electrons can go in the third electron shell?
Which shell fills with electrons first?
The diagram above shows the electronic structure of an element. Which element is it?
Which element has the electronic structure 2, 4?
Which element has the electronic structure 2, 8, 6?
Draw the electronic structure of oxygen.
Draw the electronic structure of boron.
Write out the electronic structure of phosphorus.
Write out the electronic structure of magnesium.

13. Answers – Fact Recall An energy level 2 electrons 8 electrons
The one closest to the nucleus. /The one with the lowest energy level.

14. A video on atomic structure…

15. Complete the sheet
Complete as many of the questions on the sheet as you can.

16. Answers – Application
Neon
Carbon
Sulphur
2,8,5
2,8,2

17. Electron – Negative (-)
Answers – Part A
Your atom should look like this: Element: Boron
Electron – Negative (-)
Neutron – Neutral (0)
Proton – Positive (+)

18. Answers – Part B Questions: ATOMIC NUMBER SYMBOL ELEMENT NAME
7. PROTONS or ELECTRONS
8. PROTONS and NEUTRONS
9. USE THE ATOMIC NUMBER
10. SUBTRACT THE ATOMIC NUMBER FROM THE ATOMIC MASS.
ATOMIC NUMBER
SYMBOL
ELEMENT NAME
ATOMIC MASS

19. Answers – Part C
12. 1st = 2 2nd = 8 3rd = Valence 14.

20. Answers – Part C
15.

21. Answers – Part C
16. (1) He & Ne (2) Li (only has 1 valence electron) (3) Cl (only needs 1 more electron to fill it’s outer shell. (4) He & Ne, because they have full outer shells.