How many electrons does Na have in shell \(n=1 ? n=2 ? n=3\) ?

The atomic structure is fundamental to understanding chemistry and physics. It refers to the arrangement of protons, neutrons, and electrons within an atom. Protons and neutrons are located in the nucleus at the center, while electrons revolve around the outside in specific regions called energy levels or shells.

Every element has a unique number of protons, known as its atomic number, which determines its place in the periodic table. For instance, sodium (Na) has an atomic number of 11, thus 11 protons in its nucleus. Atoms are electrically neutral when they have an equal number of protons and electrons, meaning sodium also has 11 electrons in its neutral state.

The periodic table is an organized chart of all chemical elements, ordered by increasing atomic number. It is designed so that elements with similar properties fall into the same column, known as a group or family. The rows are referred to as periods and indicate the number of shells of electrons the atoms of the elements have.

This layout helps predict the properties of elements and their compounds. For example, sodium (Na) is located in the third period and first group, which reveals that it has electrons in three shells and shares similar properties with other elements in its group.

Atoms consist of electrons in regions called energy levels or electron shells. These levels determine the distance of electrons from the nucleus and their energy state. Electrons in shells closer to the nucleus have lower energy and are more tightly bound.

According to the 2n² rule, the maximum number of electrons in a shell is given by the formula where n is the energy level number. As a result, the first energy level (n=1) can hold up to 2 electrons, the second (n=2) up to 8, and so on, which explains how electrons are distributed in an atom like sodium.

The concept of shells in atoms is critical for visualizing electron configuration. Shells are often labeled by principal quantum numbers starting at 1 and increasing outward. The innermost shell (n=1) has the lowest energy and fills with electrons first, followed by the higher numbered shells.

Electrons occupy the most stable arrangement possible by filling the lowest energy shells first, which is described by the aufbau principle. Following this principle and the 2n² rule, the electrons for sodium (Na) would be distributed as 2 in the first shell (n=1), 8 in the second shell (n=2), and 1 in the third shell (n=3). This configuration reflects the most energetically stable state for an atom's electrons.