How are electrons arranged in energy levels?

Electrons are arranged in energy levels, or shells, around the nucleus of an atom, with each level holding a specific number of electrons.

In more detail, the arrangement of electrons in an atom follows a specific pattern, known as the 'electron configuration'. This configuration is based on energy levels, also referred to as shells or orbits, which are a way of categorising the space around an atom where electrons are most likely to be found. Each energy level can hold a certain maximum number of electrons. The first energy level, closest to the nucleus, can hold up to 2 electrons. The second level can hold up to 8 electrons, and the third can also hold up to 8 electrons.

The electrons fill the energy levels in a specific order, starting with the lowest energy level (closest to the nucleus) and moving to higher energy levels as more electrons are added. This is known as the 'Aufbau Principle'. For example, if an atom has 6 electrons, 2 will be in the first energy level and the remaining 4 in the second.

The arrangement of electrons in energy levels is crucial for understanding how atoms interact with each other to form chemical bonds. For instance, atoms tend to be more stable when their outermost energy level is full, which often drives atoms to gain, lose or share electrons in order to achieve a full outer shell. This is the basis of chemical reactions.

In summary, the arrangement of electrons in energy levels is a fundamental concept in chemistry, providing a framework for understanding the behaviour of atoms and the formation of chemical bonds.