Question

What are the bond angles in phosphine( $P{H_3}$ )

Answer 1

The most important constituents of an atom consists of Proton(Positively charged species),Electrons(Negatively charged species) and Neutrons(Neutral charged).The phosphine molecule consists of four atoms.One phosphorus atom and three hydrogen atom.In the above given question we need to focus on bond angles and the factors which affect it.

Complete answer:
Bond angle: The average angle between the orbitals containing bonding electron pairs around the central atom in a molecule is defined as bond angle.The units of bond angles are degree or minute or second.It helps in giving an idea about the location of bond pairs and lone pairs as well as it tells about the location of central atoms and surrounding atoms so that we can determine the shape and geometry of the molecules.It is important to note that different molecules have different bond. The bond angle depends upon various factors like the number of lone pairs, size and electronegativity of the central atom and size of surrounding atoms.
When considering the phosphine molecule, the central atom is phosphorus which has one lone pair of electrons and three bond pairs of electrons.The Phosphorus does not undergo any form of hybridisation. All the three phosphorus hydrogen bonds are formed by the overlap of three unhybridized $p$ orbitals of phosphorus with $1s$ atomic orbitals of three hydrogen atoms. The lone pair of electrons is present in $s$ orbital. The molecular geometry is trigonal pyramidal. The bond angle which is observed in phosphine is $93.5 ^\circ$

Note:
Since the bond angle for different molecules stand to be different it needs to be determined by considering theoretical factors and practical observations.Whether a molecule undergoes hybridisation is also very important in consideration of bond angle.