A certain oxygen atom has the electron configuration 1 s^2 2...

A certain oxygen atom has the electron configuration $1 s^{2} 2 s^{2} 2 p_{s}^{2} 2 p_{y}^{2}$. 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?

Key Concepts

Energy Absorption/Release in Electronic Transitions

Electronic transitions between energy states are accompanied by energy changes. When an atom transitions from an excited state to a lower energy (ground) state, energy is released, typically in the form of photons. Conversely, moving an electron to a higher energy state requires an absorption of energy. This concept is critical for explaining spectroscopic phenomena and reaction energetics.

Ground State vs. Excited State

The ground state is the lowest energy arrangement of electrons in an atom while an excited state involves one or more electrons being promoted to higher energy orbitals. Identifying whether an electron configuration is ground state or excited state involves comparing it to the configuration predicted by Aufbau's principle and Hund’s rule, and it is important in understanding energy transitions within atoms.

Hund’s Rule of Maximum Multiplicity

Hund’s rule states that electrons will fill degenerate orbitals singly and with parallel spins before pairing up. This minimizes electron–electron repulsions and maximizes total spin, usually resulting in lower energy (more stabilized) configurations. This concept is essential for understanding why a particular electron configuration represents the ground state or an excited state.

Electron Configuration

Electron configuration describes the distribution of electrons among an atom's orbitals. It follows principles such as the Pauli Exclusion Principle and builds up in energy order. In this subject area, knowing the arrangement of electrons helps in predicting chemical properties and reactivity, and serves as the foundation for identifying ground and excited states.

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