draw the following Lewis Dot structures

[mare]

a) PCl₃

b) C

[sharan]

a) its bit hard to draw so i guess I can just try in words step by step
1. Draw a phosphoros molecule in middle since it is the centreal atom . It has five valence electron.

P
2. Draw 3 Chlorine atoms around the central atom P. Chlorine has 7 valnce electrons and in total 3 Cl has 3 x 7= 21 valence electron.

Cl

Cl P Cl

3. Now count total number of valence electrons. 21 (Cl) + 5 (P)= 26.


4. Start sharing two electrons between Cl and P since two electrons required to make bond but we are just drawing dots as you have said. So every Cl and P has two electrons shared. Now out of 26, 6 are gone . We are left with 20. Now As you know every atom needs to fulfil their oribit with 8 electrons. So we start with Cl as it already has 2 eletrons shared between P and Cl. It needs 6 more.
This way all 3 Cl need 6 electrons each .
Now 3 x 6= 18 electrons gone. We are left with two.
Observe P also has only 6 (shared between 3 Cl's) So put one under the P.
You are DONE.

Cl
..
Cl : P : Cl
..

b. It is simple just draw C in the middle and draw four electrons on each side since C has 4 valnce electrons.

Hope that helps. I hope my drawings.. you can understand. lol

-Sharan