Atomic Structure and Electronic Configuration

Vocabulary and key concepts regarding atomic components, sub-atomic particle properties, and electron shell arrangements based on the lecture notes.

Atom

The smallest particle of an element that can exist and the building block of matter.

Atomic/Proton number

The number of protons in an atom; each element has a unique proton number.

Nucleon number (Mass number)

The total number of particles in the nucleus, represented by the sum of protons and neutrons.

Proton

A positively charged sub-atomic particle found in the nucleus with a relative mass of $1$ and a relative charge of $+1$.

Neutron

A sub-atomic particle found in the nucleus with no charge and a relative mass of $1$.

Electron

A negatively charged sub-atomic particle that moves around the nucleus at high speeds in electron shells, with a relative mass of $1/1840$ and a relative charge of $-1$..

Electrically neutral

The state of an atom where the number of electrons is equal to the number of protons, resulting in zero net charge.

Nuclide notation

A representation of an atom shown as ${}_{Z}^{A}X$, where $A$ is the mass/nucleon number, $Z$ is the atomic/proton number, and $X$ is the chemical symbol.

Electron shells

Energy levels numbered $1, 2, 3, 4$ outward from the nucleus where electrons are found; the nearer the shell is to the nucleus, the lower the energy it has.

Duplet structure

The structure formed when the first shell (closest to the nucleus) is filled with $2$ electrons.

Octet structure

The structure formed when the second, third, or fourth shell is filled with $8$ electrons.

Valence electrons

The electrons found in the outermost shell of an atom.

Electronic configuration

A representation of how electrons are distributed in the different electron shells in an atom (e.g., Chlorine is $2.8.7$).

Atomic mass unit (amu)

The unit of mass assigned to protons and neutrons, which are almost equal in mass and assigned $1$ each.

Calcium electronic configuration

Since the Calcium (Ca) atom has $20$ electrons, its electronic configuration is represented as $2.8.8.2$.