Choosing the Ground State Electron Configuration for Ti²⁺
Titanium (Ti) is a transition metal with an atomic number of 22. Understanding its electron configuration, and that of its ions, requires knowledge of how electrons fill orbitals according to the Aufbau principle and Hund's rule. Let's break down how to determine the ground state electron configuration for Ti²⁺.
1. Neutral Titanium (Ti):
The neutral titanium atom has 22 electrons. Its electron configuration is typically written as: [Ar] 3d² 4s². This means it has a filled argon core ([Ar]) and two electrons in the 3d subshell and two electrons in the 4s subshell.
2. Ionization of Titanium to Ti²⁺:
When titanium loses two electrons to become the Ti²⁺ ion, it loses these electrons from its outermost shells, following the general rule of removing electrons from the highest principal energy level first. This means the 4s electrons are removed before the 3d electrons.
Therefore, the electron configuration of Ti²⁺ is: [Ar] 3d².
3. Why not [Ar] 4s⁰ 3d²?
While it might seem logical to represent it as [Ar] 4s⁰ 3d², this notation, while technically correct in terms of electron count, doesn't accurately reflect the orbital energies involved. In reality, the 3d and 4s orbitals have similar energies in transition metals, and the slight energy difference can change upon ionization. After losing the 4s electrons, the remaining 3d electrons are in lower energy levels than what a hypothetical empty 4s orbital would be. Hence, [Ar] 3d² is the preferred and more accurate representation.
Frequently Asked Questions (Addressing potential "People Also Ask" queries)
How do you determine the electron configuration of an ion?
To determine the electron configuration of an ion, you first write the electron configuration of the neutral atom. Then, if it's a cation (positive ion), remove the specified number of electrons from the highest energy levels (first removing electrons from the s-subshell of the highest energy level, then the p-subshell if needed, etc.). If it's an anion (negative ion), add the specified number of electrons to the highest energy levels.
What is the difference between the ground state and excited state electron configurations?
The ground state electron configuration represents the lowest energy arrangement of electrons in an atom or ion. Excited states occur when an electron absorbs energy and jumps to a higher energy level. The ground state is always the most stable configuration.
What are the rules for filling orbitals with electrons?
Electron configurations are determined by following the Aufbau principle (filling orbitals from lowest to highest energy), Hund's rule (maximizing unpaired electrons within a subshell), and the Pauli exclusion principle (no two electrons can have the same four quantum numbers).
Are there exceptions to the Aufbau principle in transition metals?
Yes, there are exceptions, especially in transition metals. The energies of the 3d and 4s orbitals are quite close, so the order of filling can sometimes deviate slightly from the strict Aufbau principle. This is why you see subtle variations in electron configurations of transition metal ions. However, the general principle of removing electrons from the outermost shell still applies.
In conclusion, the ground state electron configuration for Ti²⁺ is definitively [Ar] 3d². Understanding this requires a grasp of fundamental electron configuration principles and the specifics of transition metal electron behavior.
