Draw the structure of phosphorus atom according to Bohr’s model of atom. Write the valency of phosphorus. (Atomic number of phosphorus = 15)
The correct answer and explanation is:
Correct Answer:
Structure of Phosphorus Atom According to Bohr’s Model:
Phosphorus has an atomic number of 15. This means it has 15 protons in the nucleus and 15 electrons distributed in energy levels around the nucleus.
Electron distribution in shells (Bohr’s model):
- First shell (K): 2 electrons
- Second shell (L): 8 electrons
- Third shell (M): 5 electrons
Bohr Model Diagram Description (since visual drawing is not possible here):
- A small central nucleus contains 15 protons and 16 neutrons.
- Three concentric circular orbits surround the nucleus:
- The first orbit (K) holds 2 electrons.
- The second orbit (L) holds 8 electrons.
- The third orbit (M) holds 5 electrons.
Valency of Phosphorus: 3 or 5
Explanation:
Phosphorus is a non-metal with an atomic number of 15. This means it has 15 electrons arranged in shells around the nucleus according to Bohr’s atomic model. The distribution of electrons follows the 2n² rule where ‘n’ is the shell number.
For phosphorus:
- The first shell (n=1) can hold up to 2 electrons, and phosphorus uses all 2.
- The second shell (n=2) can hold up to 8 electrons, and phosphorus uses all 8.
- The third shell (n=3) can hold up to 18 electrons, but phosphorus only has 5 electrons remaining for this shell.
The outermost shell, or valence shell, contains 5 electrons. To become stable like a noble gas, an atom tends to either lose, gain, or share electrons to complete its octet. Phosphorus needs 3 more electrons to complete 8 in its outer shell, so its common valency is 3. This is often seen when phosphorus forms compounds like phosphine (PH₃).
However, phosphorus can also show a valency of 5 by expanding its octet, particularly in compounds like phosphorus pentachloride (PCl₅), due to the availability of d-orbitals. Therefore, phosphorus can exhibit valency of both 3 and 5 depending on the chemical reaction or compound it is involved in.