1. Step 1 Identify the central atom and draw it’s Lewis structure This is the element with the lowest number of atoms in the formula Draw a Lewis dot diagram for AsCl 3 As

2. Step 2 write the Lewis dot structure for all remaining atoms Draw a Lewis dot diagram for AsCl 3 Cl

3. Step 3 Connect the Atoms together by pairing up the single electron from different atoms Step 4 Replace shared electron with a dash (a dash represents two shared electrons) As Cl

4. Step 5 Check that you have included all lone pairs As Cl

5. W W W We Do! Draw the Lewis dot diagram for Nitrogen trifluoride NF 3

6. Step 1 identify the central atom This is the element with the lowest number of atoms in the formula Step 2 find the number of chemical bonds There are three chlorines attached so three chemical bonds Draw out the molecule Cl – As – Cl Cl Draw a Lewis dot diagram for AsCl 3

7. Step 3 Find the total number of valence electrons in the molecule (including any due to charges) As = 5 e- 5 Cl = 7e- x 3 21 Total = 26 Step 4 since both bonds and lone pairs both need 2 electrons so halve the total number of electrons. Subtract the number of bonds 13 electron pairs – 3 bonds = 10 e- pairs

8. Step 5 add the electron pairs to the outer atoms until full then place remaining pairs on the central atom. ( Remember to count each bond as representing two electrons) Cl – As – Cl Cl

9. W W W We Do! Draw the Lewis dot diagram for Nitrogen trifluoride