The bond angles increase steadily in the series PF3, PCl3, PBr3, and PI3. Using the concepts that you have learned in chapters 7-10, explain this observation.

See explanation

Explanation:

Electronegativity is the ability of an atom in a molecule to attract the  shared electrons of a covalent bond towards itself. Electronegativity is a trend that increases across the period and decreases down the group in the periodic table.

All the compounds listed are halides of phosphorus. The electronegativity of halogens decrease in the order; F> Cl> Br > I. Hence F has the greatest electronegativity in the group. It decreases as atomic and ionic radius increases.

As the electronegativity of the halogen atom decreases, the electron pair on the halogen atom lie closer to the central  phosphorus atom hence the repulsion between electrons increases and so does the bond angle increase likewise.

he would use the colour black