Question

The ground state for the lithium (Li) atom and the scaled energies of its shells are shown below. Draw a Bohr diagram for the lowest-energy excited state of lithium.

Short answer

The lowest-energy excited state of lithium has an electron configuration of 1s²2p¹. The Bohr model for this excited state can be drawn with a nucleus labeled 'Li', surrounded by two energy levels. The first energy level (n=1) contains two electrons in the 1s orbital, while the second energy level (n=2) contains one electron in the 2p orbital.

Step-by-step solution

Ground state electron configuration of lithium

Lithium has three electrons, so its ground state electron configuration is 1s²2s¹. Step 2: Determine the electron configuration for the lowest-energy excited state of lithium.

Lowest-energy excited state electron configuration

The lowest-energy excited state of lithium can be achieved by promoting one electron from the 2s orbital to an empty orbital, which is the 2p orbital. So, the electron configuration for the excited state is 1s²2p¹. Step 3: Draw the Bohr model for the lowest-energy excited state of lithium.

Bohr model for the lowest-energy excited state of lithium

To draw the Bohr model for the lowest-energy excited state of lithium, follow these steps: 1. Draw a small circle at the center and label it as 'Li', representing the nucleus of the lithium atom. 2. Draw the first energy level (n=1) as a circle around the nucleus. 3. Draw the second energy level (n=2) as another circle surrounding the first energy level. 4. Place two electrons (represented by dots) in the 1s orbital of the first energy level. 5. Place one electron (represented by a dot) in the 2p orbital, which is in the second energy level. You have now successfully drawn the Bohr model for the lowest-energy excited state of lithium with an electron configuration of 1s²2p¹.

Key concepts

Ground State Electron Configuration

The term 'ground state electron configuration' refers to the most stable arrangement of electrons in an atom when it is not excited by external energy.
For lithium (Li), which has three electrons, its ground state configuration is expressed as 1s²2s¹. This notation indicates that two electrons occupy the first energy level (n=1), known as the 's' orbital, and one electron occupies the second energy level in the 's' orbital. Understanding the ground state is crucial for examining changes in the atom's configuration when energy is added.

Excited State Electron Configuration

In contrast to the ground state, the 'excited state electron configuration' describes an atom with electrons that have absorbed energy and moved to higher energy levels.
For lithium, the lowest-energy excited state is realized when one electron from the 2s orbital is promoted to the higher 2p orbital, resulting in the configuration 1s²2p¹. This state is less stable and will eventually revert back to the ground state, as the electron drops down and releases energy, often as light.

Bohr Diagram

A 'Bohr diagram' visualizes the structure of an atom according to the Bohr model, showcasing how electrons are distributed among various energy levels.
When drawing a Bohr diagram for lithium's excited state, one must first denote the nucleus with 'Li' and then represent the energy levels as concentric circles. Electrons are drawn as dots: two in the 1s orbital and one in the higher-energy 2p orbital, distinguishing the excited state from the ground state configuration.

Energy Levels

Energy levels in an atom are the fixed distances from the nucleus where electrons can orbit. Each level can hold a certain number of electrons before filling up.
In the Bohr model, the first energy level (n=1) can hold up to 2 electrons, while the second (n=2) can hold up to 8. In lithium's case, the movement of one electron from the 2s orbital to the 2p orbital, although within the same principal energy level, represents a shift to a higher energy sublevel, illustrating the atom's absorption of energy and the formulation of its excited state.