 # How To Write Electron Configuration (A Guide to Know)

If you want to draw an orbital diagram or write the electron configuration of an atom, you must know the rules for doing so. Atoms with more than 18 electrons are called noble gases, and their electrons are filled in their subshells in increasing order of their ‘quantum number sum.’ You can learn about these rules by reading the following article.

## How To Write Electron Configuration

### Atoms With More Than 18 Electrons Fill Subshells in Order of Increasing ‘Quantum Number Sum

The periodic chemical behavior of atoms is accounted for by their ability to fill subshells in the order of their increasing quantum number sum. In a molecule, the first electron in an atom fills its s-orbital, followed by the p-orbital, and so forth. Each orbital has a spin quantum number, s, which represents either “up” or “down.” In order to fill an orbital, the electrons must have a parallel spin.

Atoms with more than 18 electrons fill their subshells in order of increasing quantum number. Usually, atoms with more than 18 electrons fill the outermost subshell. However, the first and last subshells in group 3A have three and four electrons, respectively. In group 4A, four electrons fill a subshell; in group 5, five electrons fill the subshells; group 6A elements have six electrons; group 7A elements are halogens and noble gases with eight electrons.

The first four letters of the alphabet are random, and then the rest are alphabetical. The next step in quantum number calculation is to calculate the total number of electrons in an atom. Then, you can determine the number of electrons in each subshell, which should be greater than one for an atom with 18 electrons. You can use the third rule of quantum numbers to find out how many electrons each atom can contain.

### Noble Gases Fill Subshells in Order Of Increasing ‘Quantum Number Sum’

The quantum number sum indicates the number of electrons a noble gas possesses. The lower the number, the fewer electrons it can hold. The higher the number, the more energy it has. An atom can contain up to eight electrons. The first subshell has two electrons, followed by a second subshell with six and a third shell with ten. Each of these subshells has a letter designation. The first two subshells are called s, and the second subshell is called p-. A noble gas’s highest number of electrons is found in halogens and fluorine.

The energy levels of electrons in each subshell are based on the principal quantum number or n. The p-subshell contains two electrons that rotate in opposite spin states. The s-subshell has one circular orbital and three dumbbell-shaped orbitals. The d-subshell contains five unique orbitals and can hold a maximum of ten electrons. Finally, the f-subshell has seven orbitals.

### Rules For Drawing the Orbital Diagram for An Atom

The orbital diagram of an atom is a picture of how electrons are positioned in an atom. These diagrams are also called configuration notations. They show the electron’s spins, which are determined by the Pauli exclusion principle and Hund’s rule. According to the latter, the most stable configuration is the one that contains the highest number of parallel spins.

In the diagram, the electrons are represented as arrows. Arrows represent the spins of the electrons, and the highest-energy orbitals are on top. The orbital filling diagrams show the electrons’ locations relative to their surrounding protons. The diagrams also show electron sharing, which is important for understanding chemical bonding.

Read Also:- How To Write a Play in 2023

The three main rules for drawing the orbital diagram for an atomic structure are Pauli exclusion, Aufbau’s principle, and Hund’s rule. These three rules determine the positions of electrons in atoms and help us draw the atom’s orbital structure.