What is the electronic configuration of Ti, which has an atomic number of 22?
A. [Ar]4s²4d²
B. [Ne]4s²3d²
C. [Ar]4s²3d²
D. [Ar]3s²3d²
The Correct Answer and Explanation is:
The correct answer is A. [Ar]4s²4d².
Explanation:
The electronic configuration of an element describes how its electrons are distributed among the orbitals. For Titanium (Ti), which has an atomic number of 22, the goal is to distribute 22 electrons into the orbitals according to the Aufbau principle (which states that electrons fill orbitals starting from the lowest energy level), the Pauli exclusion principle (which states that each orbital can hold a maximum of two electrons with opposite spins), and Hund’s rule (which states that electrons will fill degenerate orbitals singly before pairing).
The electron configuration for Ti can be broken down as follows:
- First, fill the 1s orbital:
- 1s² (2 electrons)
- Then fill the 2s and 2p orbitals:
- 2s² (2 electrons)
- 2p⁶ (6 electrons)
- Next, fill the 3s and 3p orbitals:
- 3s² (2 electrons)
- 3p⁶ (6 electrons)
- Now, we move to the 4s orbital:
- 4s² (2 electrons)
- Finally, fill the 3d orbitals:
- 3d² (2 electrons)
This leads to the electron configuration:
[ 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d² ]
However, in shorthand notation, the noble gas Argon (Ar), which has an atomic number of 18, can be used to represent the first 18 electrons. This gives the configuration as:
[ [Ar] 4s² 3d² ]
Why is this the correct configuration?
- 4s orbitals are filled before 3d orbitals because the 4s orbital is lower in energy when the atom is in its ground state. However, after ionization, the 4s electrons are typically lost before the 3d electrons.
- This configuration places the two electrons in the 4s orbital and the remaining two electrons in the 3d orbital, which is characteristic of Titanium.
The other options are incorrect because:
- B. [Ne]4s²3d² has an incorrect base, as Titanium is heavier than Neon (Ne) and should start at Argon (Ar).
- C. [Ar]4s²3d² is the correct notation, but this is duplicated in option A.
- D. [Ar]3s²3d² places the electrons in the wrong orbitals for Titanium’s ground state.