Atoms, Elements, Periodicity and Chemical Structures

Flashcards covering general chemistry basics, atomic structure, periodic trends, and fundamentals of organic chemical structures and bonding.

Atom

The basic building block of all matter, composed of protons ($+1$ charge), neutrons ($0$ charge), and electrons ($-1$ charge).

Atomic Number (Z)

The number of protons in the nucleus of an atom, which defines the specific atom type.

Mass Number (A)

The total number of protons and neutrons located in the nucleus of an atom.

Isotopes

Atoms with the same number of protons but different numbers of neutrons, resulting in different mass numbers.

Cation

A positively charged ion formed when an atom has more protons than electrons.

Anion

A negatively charged ion formed when an atom has more electrons than protons.

Compounds

Substances consisting of atoms of two or more different elements joined together, such as $NaCl$ or $H_2O$.

Mole (mol)

A conventional number equal to Avogadro's number: $6.022 \times 10^{23}$. One mole of a substance contains this many molecules.

Molarity (M)

The number of moles of solute per litre of solution, used as a unit for concentration ($mol/L$).

Relative Atomic Mass

The weighted average of all naturally occurring isotopes of an element.

Molar Mass

The mass of one mole of a substance, typically reported in grams per mole ($g/mol$ or $g\,mol^{-1}$).

Metalloids

Elements with physical and chemical properties intermediate between metals and non-metals, including $B$, $Si$, $Ge$, $As$, $Sb$, and $Te$.

Electronegativity

The power of an atom in a molecule to attract shared electrons toward itself.

Organic Chemistry

The chemistry of carbon compounds based around at least one $C-H$ bond.

Functional Groups

Specialized and reactive components attached to the carbon-hydrogen framework that confer specific chemical functionality to a compound.

Skeletal Formula

A line-angle representation of organic molecules where carbon atoms and their attached hydrogens are not shown, and each line represents a bond.

Empirical Formula

The lowest whole number ratio of elements present in a chemical compound.

Atomic Orbitals

Three-dimensional regions in space where there is a $95\%$ probability of finding an electron.

Aufbau Principle

The principle stating that orbitals and shells are filled in order of increasing energy, starting with $1s$.

Pauli Exclusion Principle

The rule that each atomic orbital can hold a maximum of two electrons, and these electrons must have opposite spins.

Hund's Rule

When filling degenerate orbitals (orbitals of equal energy), electrons occupy them singly before pairing up to minimize electron-electron repulsion.

Valence

The number of electrons an atom must gain or lose to achieve the nearest noble gas electronic configuration.

Octet Rule

The biological and chemical stability attained when an atom has eight electrons in its outermost shell.

Ionic Bonding

Chemical bonding that occurrs by the transfer of valence electrons from a metal to a non-metal, resulting in electrostatic attraction.

Covalent Bonding

Chemical bonding that occurs when electrons are shared between atoms rather than transferred.

Hydrogen Bonding

An attractive force between a hydrogen atom attached to an electronegative atom ($O$, $N$, or $F$) and another electronegative atom.

sp3 Hybridisation

The blending of one $s$ and three $p$ orbitals to create four equivalent hybrid orbitals with tetrahedral geometry and bond angles of $109.5^{\circ}$.

sp2 Hybridisation

The blending of one $s$ and two $p$ orbitals to create three hybrid orbitals with trigonal planar geometry and bond angles of $120^{\circ}$.

sp Hybridisation

The blending of one $s$ and one $p$ orbital to create two hybrid orbitals with linear geometry and bond angles of $180^{\circ}$.

Sigma (σ) bond

A bond formed by direct orbital overlap that is symmetrical around the bond axis and allows for free rotation.

Pi (π) bond

A bond formed by side-by-side overlap of $p$ orbitals that restricts rotation and maintains electron density above and below the bond axis.