Question

Which of the following is the correct electron orbital configuration of phosphorus? A. \(1 s^2 2 s^2 3 s^2 2 p^6 3 p^3\) B. \(1 s^2 2 s^2 2 p^6 3 s^2 3 p^3\) C. \(1 s^2 2 s^2 2 p^6 3 p^5\) D. \(1 \mathrm{~s}^2 2 \mathrm{~s}^2 2 \mathrm{p}^6 3 \mathrm{~s}^2 3 \mathrm{~d}^{10} 3 \mathrm{p}^6\)

Short answer

Option B. 1s^2 2s^2 2p^6 3s^2 3p^3

Step-by-step solution

- Determine the Atomic Number of Phosphorus

Look up the atomic number of phosphorus on the periodic table. The atomic number of phosphorus is 15.

- Understand Orbital Configuration Order

Recollect the order in which orbitals are filled according to the Aufbau principle: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, etc.

- Write Electron Configuration Up to 15 Electrons

Start filling up orbitals in the order: 1s^2, 2s^2, 2p^6, 3s^2, 3p^3. Add the number of electrons in these orbitals to confirm they sum up to 15 (2 + 2 + 6 + 2 + 3 = 15).

- Compare with Given Options

Compare the derived configuration (1s^2 2s^2 2p^6 3s^2 3p^3) with the given options: A. 1s^2 2s^2 3s^2 2p^6 3p^3B. 1s^2 2s^2 2p^6 3s^2 3p^3C. 1s^2 2s^2 2p^6 3p^5D. 1s^2 2s^2 2p^6 3s^2 3d^{10} 3p^6.Option B matches the electron configuration derived.

Key concepts

Atomic Number

The atomic number of an element is fundamental in understanding its electron configuration.
It tells you the number of protons in an atom's nucleus, and for a neutral atom, this is also the number of electrons.
For phosphorus, the atomic number is 15. This means a neutral phosphorus atom has 15 electrons.
These electrons are arranged in specific orbitals around the nucleus according to defined principles and patterns.

Aufbau Principle

The Aufbau principle states that electrons fill orbitals starting from the lowest energy level before moving to higher levels.
This is like filling a container from the bottom up. The word 'Aufbau' means 'building up' in German.
The sequence follows a specific order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, and so on. This principle helps predict the electron configurations of atoms.

• 1s (first level) gets filled first.
• 2s (second level) comes next.
• Then, 2p gets filled.

This pattern continues, ensuring that electrons occupy the lowest available energy level.

Orbital Filling Order

Understanding the orbital filling order is crucial for determining an element's electron configuration.
For phosphorus, with 15 electrons, the electrons fill orbitals in this order:

• 1s: 2 electrons
• 2s: 2 electrons
• 2p: 6 electrons
• 3s: 2 electrons
• 3p: 3 electrons

This gives the electron configuration: 1s^2 2s^2 2p^6 3s^2 3p^3.
Each new orbital starts filling only when the previous one gets fully occupied, ensuring stability and order in electron arrangements.

Electron Orbitals

Electron orbitals are regions around an atom's nucleus where electrons are likely to be found.
Each orbital can hold a specific number of electrons:

• s orbitals hold a maximum of 2 electrons.
• p orbitals hold a maximum of 6 electrons.
• d orbitals hold up to 10 electrons.

For phosphorus, the orbitals fill as follows: 1s^2 2s^2 2p^6 3s^2 3p^3.
This means 2 electrons fill up each 1s, 2s, 3s orbital, and the remaining 9 electrons fill the 2p and 3p orbitals.
This arrangement allows phosphorus to have all 15 electrons positioned in the lowest possible energy state, following the Aufbau principle and orbital filling order.