Question

What is meant by the phrase excited state as applied to an atom or molecule? Symbolically, how is an excited state signified?

Short answer

An excited state is when an electron absorbs energy; it is symbolically represented with an asterisk, like ${\text{H}}^{\ast }$.

Step-by-step solution

Understanding the Ground State

To understand the concept of excited states, we first need to know about the ground state. The ground state of an atom or molecule is its lowest energy state. When all electrons occupy the lowest possible energy levels, the atom is in its ground state.

Defining Excited State

An excited state occurs when one or more electrons in an atom or molecule absorb energy and move to a higher energy level than this ground state. This state is higher in energy compared to the ground state.

Symbolic Representation

The excited state is symbolically represented by an asterisk next to the chemical symbol, such as ${\text{H}}^{\ast }$ for a hydrogen atom in an excited state. Another notation is using quantum numbers, indicating electrons have transitioned to higher principal quantum levels.

Key concepts

Ground State

The concept of the "Ground State" in atom and molecule physics refers to the lowest energy state of these particles. Imagine this as the "home" or "resting place" of electrons within atoms. In the ground state, electrons occupy the lowest available energy levels, arranging themselves in what is often described as the most stable configuration. For example, in a hydrogen atom, the single electron resides in the lowest energy level closest to the nucleus in its ground state. This state is crucial because without an understanding of it, we cannot grasp more energetic states, such as the excited state. Knowing an atom’s ground state is like knowing the baseline or reference point from which changes or reactions begin.

Energy Levels

Atoms have specific regions or "shelves" where electrons are allowed to exist, known as energy levels. These levels are often seen as layers around the central nucleus of the atom. Electrons can move between these levels but must gain or lose exact amounts of energy to do so.

• - In the ground state, electrons fill up the lowest energy levels first.
• - When electrons gain energy, they can jump to higher, unoccupied energy levels resulting in an excited state.

This movement between energy levels is essential in chemical bonding, light emission, and many other fundamental processes in physics and chemistry. Thus, energy levels serve as the foundation for understanding how atoms interact with other atoms and with their environment.

Symbolic Representation

The idea of "Symbolic Representation" plays a major role in visualizing and recording the excited states of atoms. Typically, this is done through notations that reflect changes in energy levels.
One common symbolic representation is placing an asterisk (*) next to the element's symbol when an atom is in an excited state. For instance, a hydrogen atom in an excited state may be noted as ${\text{H}}^{\ast }$. This notation highlights that the atom has achieved a higher energy level. It’s like writing a note next to an item in your schoolwork indicating important changes or updates.
Additionally, quantum numbers can be used to describe these states, providing further detail about the energy level, orbital shape, and orientation the electron occupies.

Quantum Numbers

"Quantum Numbers" are essential for describing the properties of electrons in atoms. They provide a comprehensive system to encode information about the electrons’ positions and energy states. Imagine a unique "address" for every electron that tells you:

• - Which energy level it occupies (known as the principal quantum number, $n$).
• - The shape of the orbital (angular momentum quantum number, $l$).
• - Orientation of the orbital (magnetic quantum number, $m$).
• - Spin direction of the electron (spin quantum number, $s$).

These numbers provide precise details of an electron's "residence" within an atom, helping scientists predict how an electron behaves and interacts. In terms of excited states, quantum numbers can show which electron has been excited and to which higher energy level, providing a clearer picture of atomic changes.