Atoms, Elements and Compounds (Video Notes)

Vocabulary flashcards covering atoms, elements, compounds, mixtures, separation techniques, and periodic table trends as described in the video notes.

Atom

The smallest unit of an element that can exist; the building block of all substances, consisting of a nucleus of protons and neutrons with electrons around it.

Element

A substance made of only one type of atom; listed in the periodic table; about 100 elements; can be metal or non metal.

Chemical symbol

A one or two letter shorthand for an element, e.g., O for oxygen or Na for sodium.

Periodic table

A chart of elements arranged by increasing atomic number into groups and periods; shows patterns in properties.

Group

A vertical column in the periodic table; elements with similar chemical properties.

Period

A horizontal row in the periodic table; elements in the same period have the same number of electron shells.

Metal

An element that tends to form positive ions; usually located left and bottom in the periodic table.

Non-metal

An element that usually forms negative ions or shares electrons; located on the right and top of the periodic table.

Compound

A substance formed when two or more different elements are chemically bonded in fixed proportions; has different properties from its elements; represented by a formula.

Mixture

Two or more substances that are not chemically bonded; components retain properties and can be separated by physical methods.

Filtration

Separation of an insoluble solid from a liquid using a filter paper.

Filtrate

The liquid that passes through the filter paper during filtration.

Residue

The solid that remains on the filter paper after filtration.

Filter paper

Porous paper used to trap solids during filtration.

Evaporation

Separation of a soluble solid from a liquid by boiling off the solvent; crystals may form if cooled slowly.

Crystallisation

Formation of solid crystals from a solution; do not remove all water if hydrated salts are needed.

Simple distillation

Separation of a soluble liquid from a solid or mixture by boiling and condensing the liquid.

Fractional distillation

Separation of liquids with different boiling points using a fractionating column to improve separation.

Fractionating column

Column with a temperature gradient used in fractional distillation to separate components.

Liebig condenser

Condenser used to cool and condense vapour back to liquid during distillation.

Soluble solid

A solid that dissolves in a liquid to form a solution (eg salt in water).

Insoluble solid

A solid that does not dissolve in a liquid (eg sand in water).

Nucleus

The centre of the atom containing protons and neutrons; contains most of the atom's mass.

Proton

Positively charged particle in the nucleus; relative mass ~1.

Neutron

Electrically neutral particle in the nucleus; relative mass ~1.

Electron

Negatively charged particle surrounding the nucleus; very small mass.

Atomic number (Z)

Number of protons in the nucleus; equals the number of electrons in a neutral atom.

Mass number (A)

Total number of protons and neutrons in the nucleus.

Isotope

Atoms of the same element with different numbers of neutrons; same chemical properties.

Relative atomic mass (RAM)

Average mass of an element as weighted by isotopic abundances.

Energy level / electron shell

Fixed distances where electrons reside; first level holds up to 2 electrons, second and third up to 8.

Bohr model

Theory where electrons orbit the nucleus at specific energy levels.

Plum-pudding model

Early model of the atom with a positively charged sphere and embedded electrons.

Rutherford gold foil experiment

Experiment showing most alpha particles pass through, some scatter, indicating a small dense nucleus.

Nuclear model

Modern model with a nucleus containing protons and neutrons and orbiting electrons.

Mendeleev

scientist who left gaps in the periodic table for undiscovered elements and predicted properties.

Mendeleev gaps

Gaps left by Mendeleev for elements yet to be discovered; some later filled.

Modern periodic table

Periodic table organized by atomic number; groups contain elements with similar properties.

Alkali metals

Group 1 elements; 1 outer electron; metals; low density; stored under oil; highly reactive with water.

Noble gases

Group 0; unreactive; full outer electron shell (8 electrons, except helium with 2).

Halogens

Group 7 elements; seven outer electrons; diatomic molecules; form salts with metals.

Displacement reaction

A more reactive halogen can displace a less reactive halogen from a salt solution.

Transition metals

Elements between groups 2 and 3; metals with high mp and density; often colored compounds and catalysts.

Catalyst

Substance that speeds up a chemical reaction without being consumed.

Hydrogen exception

Hydrogen is an exception to the rule that metals form positive ions.

Stored under oil

Alkali metals are stored under oil to prevent reaction with air or moisture.

Chromatography

Separation technique that uses a stationary and a mobile phase to separate components by differing affinities.