Chemistry: Atomic Structure, Bonding, and Reactions Flashcards

Flashcards covering atomic structure, periodic trends, molecular geometry, intermolecular forces, and chemical reaction types based on a chemistry question bank.

Mass number

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

Isotopes

Atoms of the same element that have identical chemical properties and the same number of protons but different numbers of neutrons and mass numbers.

Ionisation energy

The energy required to remove an electron from an atom, which generally increases across a period due to an increase in effective nuclear charge.

Effective nuclear charge

The net positive charge that attracts electrons more strongly as one moves across a period in the periodic table.

Aufbau principle

The rule stating that electrons fill lower-energy orbitals first before moving to higher-energy levels, such as the sequence $1s^2 2s^2 2p^6 3s^2 3p^1$.

$s$ orbital capacity

The maximum number of electrons that can be held in an $s$ subshell, which is limited to $2$ electrons.

Trigonal pyramidal

The molecular shape of ammonia ($NH_3$) resulting from the presence of one lone pair on the central nitrogen atom causing repulsion.

Tetrahedral geometry

The molecular shape of methane ($CH_4$) characterized by bond angles of approximately $109.5^{\circ}$ and minimum repulsion between bonding pairs.

Bent shape

The molecular geometry of water ($H_2O$) with a bond angle of $104.5^{\circ}$ because lone pair-bond pair repulsion is stronger than bond pair-bond pair repulsion.

Linear molecule

A molecule like carbon dioxide ($CO_2$) that is nonpolar overall because its dipoles cancel due to symmetrical geometry.

London dispersion forces

Intermolecular forces present in all polar and nonpolar molecules due to temporary fluctuations in electron distribution.

Hydrogen bonding

A significantly strong type of intermolecular force that occurs when hydrogen is bonded to highly electronegative atoms such as $N$, $O$, or $F$.

Ion-dipole interaction

The interaction that occurs between an ion, such as $Na^+$, and polar molecules, such as water, during the dissolution process.

Decomposition reaction

A chemical reaction that involves breaking down a single compound into simpler substances, such as $CaCO_3 \rightarrow CaO + CO_2$.

Single displacement reaction

A reaction where one element replaces another in a compound, such as $Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$.

Exothermic reaction

A reaction classified by the release of heat to the surroundings, leading to an increase in temperature.

Endothermic reaction

A reaction classified by the absorption of heat from the surroundings, leading to a decrease in temperature.

Combination reaction

A reaction where two substances combine to form a single product, such as $H_2 + Cl_2 \rightarrow 2HCl$.

Catalyst

A substance that increases the rate of a chemical reaction by lowering the activation energy without being consumed.

Atomic radius

A property that generally decreases across a period due to increased nuclear charge and increases down a group due to an increase in electron shells.

$$2n^2$$

The formula used to calculate the maximum number of electrons a principal energy level ($n$) can accommodate; for example, level $n=3$ can hold up to $18$ electrons.

Polar covalent bond

A bond characterized by the unequal sharing of electrons due to a difference in electronegativity between the atoms.

Shielding effect

The reduction in attraction between the nucleus and external electrons that increases as more electron shells are added down a group.

Ionic compound conductivity

The property of conducting electricity in a molten state or aqueous solution because ions are free, while remaining non-conductive as a solid where ions are fixed.

Trigonal planar

A molecular shape with no lone pairs on the central atom and bond angles of $120^{\circ}$, such as in boron trifluoride ($BF_3$).

Le Chatelier’s Principle (Pressure)

A rule stating that if pressure is increased in a gaseous reaction, the equilibrium will shift toward the side with fewer moles of gas.

Reversible reaction at equilibrium

A state in a reaction where the rate of the forward reaction is equal to the rate of the reverse reaction.

Metallic bonding

A type of bonding where electrons are delocalized, allowing metals to conduct electricity.