Question

A certain oxygen atom has the electron configuration \(1 s^{2} 2 s^{2} 2 p_{x}^{2} 2 p_{y}^{2} .\) How many unpaired electrons are present? Is this an excited state of oxygen? In going from this state to the ground state, would energy be released or absorbed?

Short answer

The given oxygen atom has 0 unpaired electrons and is in an excited state. When transitioning from this state to the ground state, energy is released.

Step-by-step solution

Understanding electron configuration

We need to understand what the given electron configuration means. Electron configurations are shorthand notations for describing the arrangement of electrons in an atom. The format is: \(n\ell^{x}\) where \(n\) is the principal quantum number, \(\ell\) is the orbital type (s, p, d, or f), and \(x\) is the number of electrons in the orbital. For the given oxygen atom, the electron configuration is: \(1s^2 2s^2 2p_x^2 2p_y^2\)

Identifying unpaired electrons

Now we will determine the number of unpaired electrons in the oxygen atom: For each orbital \(\ell\), the maximum number of electrons allowed is \(2(2\ell + 1)\). In the given configuration, \(1s^2\): 2 electrons, both paired (maximum is 2 for s orbitals) \(2s^2\): 2 electrons, both paired (maximum is 2 for s orbitals) \(2p_x^2\): 2 electrons, both paired (maximum is 6 for p orbitals) \(2p_y^2\): 2 electrons, both paired (maximum is 6 for p orbitals) As all electrons are paired, there are **0 unpaired electrons**.

Identifying the excited state

To determine if this is an excited state of oxygen, let's compare the given configuration to the ground state electron configuration for an oxygen atom. In ground state oxygen, with 8 electrons, the configuration is: \(1s^2 2s^2 2p^4\) or more explicitly: \(1s^2 2s^2 2p_x^2 2p_y^1 2p_z^1\) Comparing the given configuration with the ground state configuration, we observe that one electron has been promoted from the \(2p_y\) orbital to the \(2p_x\) orbital. Since the given electron configuration has an electron promotion, we can conclude that the atom is in an **excited state**.

Energy released or absorbed

To go from the excited state to the ground state, the promoted electron in the \(2p_x\) orbital must return to the \(2p_y\) orbital. When electrons transition from a higher energy state to a lower energy state, energy is released in the form of a photon. Therefore, in transitioning from the excited state to the ground state, **energy is released**.

Key concepts

Unpaired Electrons

One of the fundamental aspects to understand when studying atoms is the concept of unpaired electrons. These are electrons in an atom that are not paired with another electron in the same orbital. The paired status is significant because electrons spin, and in a paired configuration, one electron spins in one direction while its pair spins in the opposite. This behavior affects how an atom interacts with magnetic fields and contributes to chemical bonding.

For example, in the solved exercise, we analyzed the electron configuration of an oxygen atom which was given as \(1s^2 2s^2 2p_x^2 2p_y^2\). To find unpaired electrons, we checked each orbital for their electron count. Since the maximum number of electrons in an s orbital is 2 and in a p orbital is 6, and all electrons in the configuration were paired, we concluded that there are no unpaired electrons in this particular oxygen atom. Knowing the presence or absence of unpaired electrons is crucial in determining the magnetic properties of an atom and understanding its chemical reactivity.

Excited State of Oxygen

Atoms can exist in various energy states. The lowest energy state is known as the ground state, and any state with higher energy is an excited state. The assignment asked if the electron configuration \(1s^2 2s^2 2p_x^2 2p_y^2\) represents an excited state of oxygen. To determine this, we compared the given configuration to oxygen's ground state configuration, which is \(1s^2 2s^2 2p^4\) or, when articulated in detail, \(1s^2 2s^2 2p_x^2 2p_y^1 2p_z^1\).

Upon comparison, we notice that in the given configuration, an electron has been moved from the \(2p_y\) or \(2p_z\) orbital to the \(2p_x\) orbital, creating an electron promotion. This means the oxygen atom has absorbed energy, lifting an electron to a higher orbital, and thus the atom is indeed in an excited state. Understanding the concept of excited states is essential to grasp the mechanics of energy absorption and emission in atomic structures.

Energy Transition in Atoms

The concept of energy transition in atoms is vividly demonstrated by electrons changing their energy levels. When an electron in an atom jumps from a higher energy level to a lower one, energy is emitted, often in the form of light. Conversely, energy is absorbed when an electron jumps to a higher energy level from a lower one.

Bringing our attention back to the exercise, it questioned whether energy would be released or absorbed when the oxygen atom transitions from the excited state to the ground state. The answer? Energy is released. This release of energy upon transitioning to a lower energy state is a fundamental property observed in phenomena such as the emission spectra of atoms and plays a vital role in chemical reactions and in the generation of light. The energy transitions of atoms are cornerstones in studies like spectroscopy and quantum mechanics, enabling us to understand the intricate behaviors of atoms and their interactions with energy.