Chemistry Study Guide: Atomic Structure, Ions & Electron Configurations

Comprehensive practice flashcards defining core vocabulary terms on atomic structure, subatomic particles, ions, periodic families, electron configurations, and orbital filling rules.

Proton

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

Neutron

A fundamental subatomic particle located in the nucleus with the symbol $n$ or $n^0$, a relative charge of $0$, and a mass of $1\,\text{amu}$.

Electron

A fundamental subatomic particle residing in the electron cloud / shells with the symbol $e^-$, a relative charge of $-1$, and a mass of approximately $0\,\text{amu}$ ($\frac{1}{1836}$).

Atomic Number ($Z$)

The number of protons in an atom's nucleus that determines the identity of the element.

Mass Number ($A$)

The total number of protons plus neutrons in an atom ($A = \text{Protons} + \text{Neutrons}$).

Net Charge

The difference between the number of protons and electrons in a particle ($\text{Net Charge} = \text{Protons} - \text{Electrons}$).

Nuclide Symbol Notation

A notation formatted as $^A_Z\text{X}$, where $\text{X}$ is the element symbol, $A$ is the mass number, and $Z$ is the atomic number.

Cation

A positively charged ion formed when a neutral atom loses electrons, resulting in $\text{Protons} > \text{Electrons}$.

Anion

A negatively charged ion formed when a neutral atom gains electrons, resulting in $\text{Electrons} > \text{Protons}$.

Isoelectronic Species

Atoms and ions that possess the exact same total number of electrons and identical electron configurations.

Valence Electrons

Electrons located in the outermost principal energy level of an atom that determine its chemical properties and reactivity.

Group 1 (Alkali Metals)

Periodic table elements possessing $1$ valence electron that form a common ion charge of $+1$ by losing $1\,e^-$.

Group 2 (Alkaline Earth)

Periodic table elements possessing $2$ valence electrons that form a common ion charge of $+2$ by losing $2\,e^-$.

Group 16 (Oxygen Group)

Periodic table elements possessing $6$ valence electrons that form a common ion charge of $-2$ by gaining $2\,e^-$.

Group 17 (Halogens)

Periodic table elements possessing $7$ valence electrons that form a common ion charge of $-1$ by gaining $1\,e^-$.

Group 18 (Noble Gases)

Inert elements with a stable outer shell of $8$ valence electrons ($\text{He}$ has $2$) and a common charge of $0$.

Aufbau Principle

A fundamental rule stating that electrons must occupy the lowest energy orbital available first before occupying higher energy levels.

Pauli Exclusion Principle

A fundamental rule stating that an orbital can hold at most two electrons, and they must have opposite spins ($\uparrow\downarrow$).

Hund's Rule

A rule stating that when filling degenerate orbitals of equal energy, one electron enters each orbital with parallel spins before any orbital receives a second paired electron.

Ground State

The lowest possible energy state of an atom, where electrons occupy orbitals in strict accordance with the Aufbau principle.

Excited State

A state that occurs when an atom absorbs energy, causing one or more electrons to jump to a higher principal energy level and leaving an inner shell incompletely filled.

Light Emission

The release of energy in the form of light (photons) that occurs when an excited electron returns or falls from a higher energy level back to a lower energy level.