Question

What is the oxidation state of phosphorus in $PC{l_5}$?

Answer 1

In chemistry, periodic tables play a vital role. Now we are using a modern periodic table. This modern periodic table consists of totally $118$ elements. In the periodic table there are totally $18$ columns and $7$ rows. The columns are called groups. Hence, $18$ groups in the periodic table. The rows are called periods. Hence, totally $7$ period in the table.

Complete answer:
The oxidation state of the chlorine is$- 1$. The number of chlorine is five in phosphorus pentachloride. The oxidation state of the atoms in the molecules is equal to zero.
The five chlorine atoms and one phosphorus atom in phosphorus pentachloride.
The oxidation state of phosphorus in phosphorous pentachloride is calculated,
$0 = 5\left( { - 1} \right) + x$
$0 = - 5 + x$
$x = + 5$
Here x is the oxidation state of the phosphorus in phosphorus pentachloride.
The oxidation state of phosphorus in phosphorus pentachloride is $+ 5$.
According to the above discussion, we conclude the oxidation state of phosphorus in $PC{l_5}$ is $+ 5$.

Additional information:
In general, modern periodic table ordering is based on the atomic number of the atoms. The lowest atomic number starting from the first and followed by a higher atomic number.
Depending on the energy level of the outermost shell in the atoms, periods are classified and place the atom in respect period. Depending on the electrons shielding and size and physical behaviour of the atom, groups are coming. In the modern periodic table metallic atoms are placed in the left side of the table and non-metallic atoms are placed in the right side of the table. Metalloids and transition elements are placed in between metal and non-metal elements. Below the two rows are there. There are nothing but lanthanides and actinides. These are f-block elements.

Note:
We have to remember that the atomic number of the element is nothing but the number of electrons or number of protons. The mass number of the atom is nothing but the sum of the number of protons and number of neutrons. In general we move left to right metallic property of the atom decreases. We move right to left and non-metallic property decreases.