Question

The electronic configuration of an element is \(1 \mathrm{~s}^{2} 2 \mathrm{~s}^{2}\) \(2 p^{6} 3 s^{2} 3 p^{6} 3 d^{5} 4 s^{1} .\) This represents: (a) Excited state (b) Ground state (c) Cationic form (d) Anionic form

Short answer

(a) Excited state

Step-by-step solution

Identify Electron Configuration

The electron configuration given is \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^1\). This represents the distribution of electrons across the atomic orbitals according to increasing energy levels.

Count the Electrons

Start counting the total number of electrons: \(1s^2 + 2s^2 + 2p^6 + 3s^2 + 3p^6 + 3d^5 + 4s^1 = 25\) electrons. This indicates that the element with this configuration is manganese (Mn), which has atomic number 25.

Compare with Standard Electron Configuration

The ground state electron configuration for manganese is \([Ar] 3d^5 4s^2\), or explicitly \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^2\). The given configuration \(3d^5 4s^1\) indicates an electron has moved from the \(4s\) orbital to the \(3d\) orbital.

Determine the State of the Configuration

Since an electron in manganese has moved from a higher energy orbital \(4s\) to a lower energy \(3d\) orbital in what typically would be the ground state, but here is represented as \(3d^5 4s^1\), this indicates an excited state rather than the normal lowest energy configuration.

Key concepts

Excited State

An excited state occurs when an atom absorbs energy, causing an electron to jump from its normal (or ground) orbital to a higher energy orbital. However, sometimes the movement results in an electron being placed in a lower energy orbital that is not typically occupied in the ground state. This is what happens with manganese in the given example.

In the usual scenario, electrons fill orbitals in an order of increasing energy, according to the Aufbau principle. This means the lower energy orbitals fill first before higher ones do. For manganese, you would typically see the configuration \([Ar] 3d^5 4s^2\), where the 4s orbital is fully occupied before moving electrons into the 3d orbital.

But in the excited state configuration \(3d^5 4s^1\), an electron from the 4s orbital moves to the 3d orbital, leaving the 4s with only one electron. This rearrangement reflects an excited state because it doesn't follow the typical energy ordering. Remember that excited states can make atoms temporarily more reactive as they seek stability by returning to their grounded arrangement.

Manganese

Manganese is a transition metal, located in group 7 of the periodic table, with an atomic number of 25. This means it has 25 protons in its nucleus and, in its neutral state, an equal number of electrons orbiting around it.

Manganese is known for its critical role in various industrial processes, such as steel production, due to its strengthening properties. It is also crucial for biological processes, acting as a cofactor in several essential enzymes.

The electron configuration of manganese in its ground state is \([Ar] 3d^5 4s^2\). However, when manganese is in its excited state, one of its electrons in the 4s subshell can move to the 3d subshell, leading to a configuration of \(3d^5 4s^1\). This movement affects not only its chemical behavior but also how it interacts with electromagnetic radiation, contributing to the characteristic properties of manganese.

Atomic Orbitals

Atomic orbitals are regions in an atom where electrons are most likely to be found. Each orbital can hold a specific number of electrons based on its shape and size, which are defined by quantum numbers.

There are different types of orbitals:

• \(s\)-orbitals: Spherical shape, one per energy level, can hold up to 2 electrons.
• \(p\)-orbitals: Dumbbell shape, three per energy level starting from the second, can hold up to 6 electrons in total.
• \(d\)-orbitals: More complex shapes, five per energy level starting from the third, holding up to 10 electrons in total.
• \(f\)-orbitals: Even more complex, seven per energy level starting from the fourth, holding up to 14 electrons in total.

The arrangement and filling of these orbitals follow the "Aufbau" principle, which suggests that electrons occupy the lowest available energy orbitals first. In manganese, the electron transitions from the 4s to the 3d orbital indicate an anomaly due to energy level proximities, which showcases the complex nature of these orbitals.