Chemistry Units 1 & 2 Practice Assessment Vocabulary

Vocabulary flashcards covering core chemical concepts, bonding models, stoichiometry, periodic trends, analytical methods, and kinetics from Chemistry Units 1 and 2 practice assessments.

Subatomic Particles of ${}^{41}\text{K}^+$

A potassium ion with mass number $41$ containing $19$ protons, $22$ neutrons, and $18$ electrons.

Atomic Radius Trend

The distance from the nucleus to the outermost shell of electrons, which decreases across a period due to increasing nuclear charge and increases down a group; for example, potassium ($\text{K}$) has a larger atomic radius than fluorine ($\text{F}$) or neon ($\text{Ne}$).

Disilicon Hexabromide

The systematic covalent name for the chemical compound represented by the molecular formula $\text{Si}_2\text{Br}_6$.

Thermochemical Reaction of Ethanol Combustion

An exothermic combustion reaction represented by $\text{CH}_3\text{CH}_2\text{OH}(l) + 3\text{O}_2(g) \rightarrow 2\text{CO}_2(g) + 3\text{H}_2\text{O}(l)$ with an enthalpy change of $\Delta H = -1364\,kJ\,mol^{-1}$.

Calcium Electron Configuration

The arrangement of electrons in subshells for a ground-state calcium atom ($Z = 20$), written as $1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,4s^2$.

Atomic Absorbance Spectroscopy (AAS)

An analytical technique used to determine the concentration of metal ions (such as cadmium) in a solution by measuring light absorbance against a standard linear calibration curve.

Isotopic Mass and Abundance

Quantitative properties used to determine relative atomic mass; for argon, the predominant naturally occurring isotope has an atomic mass of $39.95\,\text{amu}$ with a relative abundance of $99.60\%$.

First Ionisation Energy

The amount of energy required to remove one mole of electrons from one mole of gaseous atoms; non-metals exhibit high values (such as $1146\,kJ\,mol^{-1}$ and $1357\,kJ\,mol^{-1}$) whereas metals exhibit lower values (such as $409\,kJ\,mol^{-1}$ and $556\,kJ\,mol^{-1}$).

Flame Test

A qualitative analytical procedure used to distinguish between different metal cations based on the specific emission spectra color produced in a flame, such as differentiating calcium salts from potassium salts.

Empirical Formula

The simplest whole-number ratio of atoms of each element present in a compound; for instance, $\text{CH}_2\text{O}$ is the empirical formula for glucose ($\text{C}_6\text{H}_{12}\text{O}_6$).

Covalent Network Solid

A solid substance characterized by an extremely high melting point (e.g., $3550\,^\circ\text{C}$), zero electrical conductivity in solid and liquid states, insolubility in water and non-polar solvents, and resistance to physical deformation under impact.

Trigonal Planar Molecular Geometry

A molecular geometry predicted by VSEPR theory where three bonding pairs surrounding a central atom lie flat in a single plane at bond angles of $120^\circ$ with no lone pairs (e.g., boron trifluoride, $\text{BF}_3$).

Saturated Solution

A chemical solution in which no additional solute can dissolve at a specified temperature in the presence of undissolved solute.

Hydrogen Bonding

A strong form of intermolecular dipole-dipole attraction that occurs between a hydrogen atom covalently bonded to a highly electronegative atom ($\text{N}$, $\text{O}$, or $\text{F}$) and a lone pair on a neighboring electronegative atom.

Thin Layer Chromatography (TLC)

A chromatographic technique using a stationary phase (e.g., silica plate) and a mobile phase (liquid solvent) to separate components of a mixture based on polar affinities.

Retardation Factor ($R_f$)

The ratio of the distance traveled by a solute spot to the distance traveled by the solvent front, measured from the origin line on a chromatogram.

Collision Theory

A model stating that a chemical reaction occurs only when reactant particles collide with an energy equal to or greater than the activation energy ($E_a$) and with correct orientation.

Strong Acid vs Concentrated Acid

A strong acid completely ionises in aqueous solution regardless of concentration (e.g., $\text{H}_2\text{SO}_4$), whereas concentration refers solely to the quantity of acid solute present per unit volume of solution.

Avogadro's Law

A gas principle stating that equal volumes of different gases at the same temperature and pressure contain equal numbers of gas particles.

Selective Precipitation

A process of separating mixed cations in solution by adding a reagent that selectively forms an insoluble precipitate with specific ions (e.g., adding $\text{HI}$ precipitates $\text{Pb}^{2+}$ and $\text{Ag}^+$ as insoluble iodides).

Polar Molecule

A molecule possessing asymmetric polar bonds that yield a net molecular dipole moment and unequal electron distribution, such as methanol ($\text{CH}_3\text{OH}$).

Instantaneous Rate of Reaction

The rate of a reaction at a specific time point, calculated as the gradient of the tangent line drawn to a concentration-time graph at that exact moment.