Atomic Structure, the Periodic Table, and Ionic Bonding

Proton

A subatomic particle located in the nucleus with a positive charge ($p^+$) and a relative mass of $1\,\text{amu}$.

Neutron

A subatomic particle located in the nucleus with a neutral charge ($n^\circ$) and a relative mass of $1\,\text{amu}$.

Electron

A subatomic particle located in the electron cloud outside the nucleus in energy levels, possessing a negative charge ($e^-$) and a relative mass that is nearly negligible ($0\,\text{amu}$, or approximately $\frac{1}{2000}\,\text{amu}$).

Neutral Atom

An atom that has an equal number of protons and electrons ($p^+ = e^-$), resulting in no net electrical charge.

Atomic Number

The number of protons in the nucleus of an element, which uniquely identifies the element and never changes.

Atomic Mass

The weighted average of all naturally occurring isotopes of an element, represented as a decimal value read directly from the periodic table.

Mass Number

The combined total number of protons and neutrons in an atom, which is always expressed as a whole number.

Number of Neutrons Formula

The mathematical relationship used to calculate neutrons in an atom: $\text{Neutrons} = \text{mass number} - \text{atomic number}$.

Isotopes

Atoms of the same element containing the same number of protons but different numbers of neutrons, resulting in different mass numbers while remaining chemically alike.

Bohr Model

A structural diagram displaying all subatomic particles of an atom, with protons and neutrons placed in the central nucleus and electrons arranged in outer circular energy levels.

Bohr Model Shell Capacities

The electron capacity guidelines for energy levels in a Bohr model: the first energy shell holds a maximum of $2$ electrons, while the second and third energy shells each hold up to $8$ electrons.

Average Atomic Mass Formula

The formula used to determine atomic mass: $\text{Average Atomic Mass} = [\text{Mass number} \times \text{Percent abundance in nature}]_1 + [\text{Mass number} \times \text{Percent abundance in nature}]_2 + \dots$.

Groups (Periodic Table)

The $18$ vertical columns on the periodic table (numbered $1$ to $18$ under the IUPAC system) containing elements that exhibit similar chemical properties due to sharing the same number of valence electrons.

Periods (Periodic Table)

The horizontal rows on the periodic table that indicate the total number of electron energy levels or shells an element possesses.

Metals

Elements positioned to the left of the periodic table staircase that are generally solid at room temperature, possess high conductivity and density, are ductile and malleable, and easily lose electrons.

Nonmetals

Elements positioned to the right of the periodic table staircase that are generally solids or gases at room temperature, have low conductivity and density, are brittle (not ductile or malleable), and tend to gain electrons.

Metalloids

Elements located along either side of the staircase (including $\text{B}$, $\text{Si}$, $\text{Ge}$, $\text{As}$, $\text{Sb}$, $\text{Te}$, and $\text{Po}$, with the exception of Aluminum and Astatine) that are solid at room temperature and exhibit properties of both metals and nonmetals.

Alkali Metals

The metallic elements located in Group $1$ of the periodic table that lose $1$ valence electron to form ions with a $+1$ charge.

Alkaline Earth Metals

The metallic elements situated in Group $2$ of the periodic table that lose $2$ valence electrons to form ions with a $+2$ charge.