Determining ionic character vs covalent

[Aj1156]

To calculate the difference in electro negativity such as PCl3 would you simply do (electronegativity of P) - (electronegstivity of Cl) or would you do (electronegativity of P) - (3 x electronegstivity of Cl)

[JulieAljamal1E]

I believe you subtract the electronegativity of Phosphorus from that of Chlorine since chlorine is more electronegative. Thus it would be 3.16-2.19=0.97 electronegativity difference.

[905096106]

You calculate the individual electronegativities of the p-cl bond and then add them together.

[cara_cavarretta_3F]

On a related note, do you know if we will be responsible for knowing exact electronegativity values or should we just know the general trend?