Question

Chemical formula of the phosphorus molecule is
A. $P$
B. ${P_4}$
C. ${P_2}$
D. ${P_3}$

Answer 1

To answer this question, you must recall the electronic configuration and structure of phosphorus. Phosphorus in the ground state can form three bonds and using this information we can arrange various phosphorus atoms in such a way so as to form the most stable structure for the molecule.

Complete step by step solution:
- Phosphorus is represented by the chemical symbol P. It has atomic number 15 and is a member of group 15 and period 3 of the periodic table. It is a non- metal in the p block and is highly reactive. The electronic configuration of the atom in its ground state can be written as:
$P:\left[ {Ne} \right]3{s^2}3{p^3}$
- Commonly, phosphorus exists in two major forms, namely white phosphorus and red phosphorus. Phosphorus is highly reactive and it is not found on the earth in the elemental form. It is generally found as phosphates.
- Phosphorus has 3 electrons in its $3p$ orbital and can thus form three bonds in the ground state. So each phosphorus forms three bonds and the molecule of phosphorus exists as ${P_4}$. It exists in the gaseous state as white phosphorus as ${P_4}$ molecule which has a tetrahedral shape.

Thus, the correct answer is B.

Note: Symbols are used commonly for the representation of elements in the modern periodic table since the names of elements can be long and complex to use. Chemical formulae and equations are also depicted using the chemical symbols of the constituent elements. Without symbols, the representation of all the 118 elements would be a very difficult task.