Question

covalent diagram for h2c and for CHCl3

Answer 1

There is no such thing as H2C. The smallest hydrocarbon is methane.
Here is a diagram for chloroform:

Answer 2

Each atom should have 8 electrons, a bond represents two electrons, those lines he drew around his Cl atoms represent electrons, if you count each atom has 8 electrons, except hydrogen which only needs 2 electrons to be more like helium