Chapter 6 & 7 Revision: Atomic Structure, Radioactivity, and Chemical Reactions

Comprehensive vocabulary flashcards reviewing atomic models, subatomic particles, isotopes, radioactive decay, chemical energy changes, acids and bases, combustion, and scientific variables.

John Dalton's Atomic Theory

The scientific theory proposing that all matter is composed of extremely small, indivisible particles called atoms.

J.J. Thomson's Atomic Model

An atomic model proposing that an atom consists of a positive sphere embedded with negatively charged electrons.

Rutherford's Alpha Particle Experiment

An experiment that revealed the atom contains a dense, positively charged central region known as the nucleus.

Bohr Model

An atomic model proposing that electrons travel in fixed energy shells or orbits around the central nucleus.

Bohr Diagram of Nitrogen

A diagram depicting a central nitrogen nucleus surrounded by two electron shells containing $2$ inner electrons and $5$ outer valence electrons, for a total of $7$ electrons.

Proton

A positively charged subatomic particle located in the nucleus of an atom, with a relative mass of approximately $1$.

Neutron

An uncharged (neutral) subatomic particle located in the nucleus of an atom, with a relative mass of approximately $1$.

Electron

A negatively charged subatomic particle located in energy shells outside the nucleus, with negligible mass.

Atomic Number

The number of protons found in the nucleus of an atom, which uniquely identifies and dictates what element it is.

Mass Number

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

Atomic Charge

The net electrical charge of an atom, calculated as the difference between the number of positive protons and negative electrons ($\text{atomic charge} = \text{number of protons} - \text{number of electrons}$).

Isotopes

Atoms of the same element that share the same atomic number (number of protons) but have different numbers of neutrons and therefore different mass numbers, such as Carbon-$12$ and Carbon-$14$.

Alpha ($\alpha$) Radiation

A type of nuclear radiation consisting of heavy particles with low penetration strength and short travel distance.

Beta ($\beta$) Radiation

A type of nuclear radiation consisting of high-speed electrons with moderate penetration strength and travel distance.

Gamma ($\gamma$) Radiation

A form of high-energy electromagnetic radiation lacking mass or charge, possessing very high penetration strength and long travel distance.

Half-Life

The time required for half of the radioactive nuclei in a given radioactive substance to decay into another substance.

Decay Curve for Iodine-131

A graphical representation of exponential radioactive decay showing that the percentage of iodine-$131$ remaining halves every $8\text{ days}$, confirming its half-life is $8\text{ days}$.

Law of Conservation of Mass

The fundamental principle stating that mass is neither gained nor lost in chemical reactions; the total mass of the reactants always equals the total mass of the products.

Law of Constant Proportions

The chemical law stating that a given chemical compound always contains its component elements in fixed, definite proportions by mass.

Endothermic Reaction

A chemical reaction that absorbs energy from the surroundings, resulting in products that possess higher chemical energy than the reactants.

Exothermic Reaction

A chemical reaction that releases energy to the surroundings, resulting in products that possess lower chemical energy than the reactants.

Reaction Energy Profile

A diagram displaying the change in potential energy across the direction of a reaction, showing energy absorbed in endothermic processes and energy released in exothermic processes.

Photosynthesis

An endothermic biological reaction ($\text{water} + \text{carbon dioxide} \rightarrow \text{glucose} + \text{oxygen}$) where plants absorb energy from the sun to synthesize glucose and produce oxygen.

Cellular Respiration

An exothermic chemical reaction occurring in living organisms that burns sugars using oxygen to release energy, serving as the reverse reaction of photosynthesis.

Acid

A chemical substance with a pH value below $7$ that reacts with bases to form a salt and water.

Base

A chemical substance with a pH value above $7$ that reacts with acids to produce a salt and water.

pH Scale

A numerical scale measuring the acidity or alkalinity of a substance, where $7$ is designated as neutral.

Universal Indicator

A chemical indicator solution that produces a range of distinct color changes corresponding to different pH values across the pH scale.

Neutralisation Reaction

A chemical reaction between an acid and a base that produces a salt and water ($\text{acid} + \text{base} \rightarrow \text{salt} + \text{water}$).

Combustion Reaction

A chemical reaction in which a fuel reacts with oxygen from the air to produce carbon dioxide, water vapour, and heat.

Independent Variable

The variable deliberately manipulated or changed by the experimenter to test its effect (e.g., adding vinegar to plant water).

Dependent Variable

The variable being measured or recorded in an experiment to observe the effect of the independent variable (e.g., the weekly height of the plants).

Control Variables

The variables kept constant throughout an experiment to ensure fair testing (e.g., same sunlight, temperature, soil type, and amount of water).