Methylphosphine (CH3PH2\text{CH}_3\text{PH}_2CH3PH2) can be represented as RPH2\text{RPH}_2RPH2 and its protonated form, the methylphosphonium ion ([CH3PH3]+[\text{CH}_3\text{PH}_3]^+[CH3PH3]+), can be represented as [RPH3]+[\text{RPH}_3]^+[RPH3]+.
Describe or draw the three-dimensional shapes around the phosphorus atom in RPH2\text{RPH}_2RPH2 and in [RPH3]+[\text{RPH}_3]^+[RPH3]+. Include any lone pairs on the phosphorus atom.
State whether the H−P−H\text{H}-\text{P}-\text{H}H−P−H bond angle in RPH2\text{RPH}_2RPH2 is greater than, the same as, or smaller than that in [RPH3]+[\text{RPH}_3]^+[RPH3]+.
Explain your answer in terms of electron pair repulsion theory.
