Bohr Models and Lewis Dot Diagrams

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Every element wants to be a because they have full valence e-, and are stable!!

Slide 12

Secret way to tell how many Valence e- in each element…

Look at your periodic table

Locate the 1 vertical row, the 2nd, then skip over to the 13th, 14th all the way to the 18th.

The last digit of each vertical row number is the amount of valence electrons

Row 1 – all elements in that row have 1 valence e- ( 1 e- in the last shell), Row 2 – all elements in that row have 2 valence e-.

Row 13 - all elements in that row have 3 valence e- , so row 18 has 8 valence e-(a full outer orbit) except Helium which has a full outer orbit of 2e-)

Slide 13

Lewis Dot Diagrams…

Gilbert Lewis used a different model than Bohr, and he only showed the valence e- in it.

His model is called the Lewis dot structure .He put dots around the symbols so that we can see just the valence electrons for the elements (so we can easily see which e- are going to react)

Slide 14

The red dots show you the valence electrons in each element’s atoms

Slide 15

Lewis Dot Structures

Slide 16

See the difference?? . Lewis just shows the valence e-

P: 11

N:12

Bohr model of Sodium Atom

Lewis Structure of Sodium Atom

Na

Slide 17

Lewis Dot Structures

Lewis dot structures are really simple – they are just the valence e- represented as dots around an element.

2 electrons together is called a lone pair.

The # of valence e- is … 8

8 e- is stable.

when atoms have a full 8 valence orbit – we call it a stable octet

Slide 18

How to draw …

Slide 19

Try some …

Remember, up to 4 e-, you put separately on each side of the symbol, once you get to 5, you have to start pairing up.

1) Magnesium 2) Nitrogen

3) Flourine 4) Argon

Mg

N

F

Ar

Bonding pair

Lone pair

Slide 20

Things to KnOw…

Every element wants to have a full outer orbit – then they are stable – so…

if an element has it’s 1st orbit full and stable – it will have 2 valence e-

if an element has it’s 2nd , or 3rd orbit full and stable – it will have 8 valence e- (we call that a Stable octet)