Elements, Compounds & Mixtures

Flashcards covering the properties of elements, compounds, and mixtures, atomic structure, the periodic table, and the history of atomic theory.

Atom

The smallest unit of a chemical element and the building block of every substance in the universe.

Element

A substance made of only one type of atom.

Compound

A substance made of two or more different types of atoms chemically bonded together.

Mixture

Any combination of compounds and/or elements that are not chemically bonded together.

Metal

An element that is typically shiny, malleable, strong, and a good conductor of heat and electricity.

Non-metal

An element that is typically dull, brittle, weak, and a poor conductor of heat and electricity.

Metalloid

An element that shares both metal and non-metal properties.

Proton

A sub-atomic particle found in the nucleus with a mass of $1$ and a charge of $1+$.

Neutron

A sub-atomic particle found in the nucleus with a mass of $1$ and no charge.

Electron

A sub-atomic particle with a mass of $0$ and a charge of $1-$ that orbits the nucleus in shells.

Atomic Number

The number of protons in an atom, which determines the identity of the element.

Mass Number

The total number of protons and neutrons in an atom ($\text{protons} + \text{neutrons}$).

Nuclide Notation

A shorthand representation of an element showing the chemical symbol with the mass number on top and the atomic number on the bottom.

Electron Shells

The orbits surrounding a nucleus; the stable configuration for the first four shells is $2, 8, 8$, and $18$ electrons.

Valence Electrons

The electrons located in the outer-most electron shell of an atom.

Period

A horizontal row on the periodic table; the period number equals the number of electron shells occupied.

Group

A vertical column on the periodic table; the group number (except for helium) indicates the number of valence electrons.

Ion

An atom that has lost or gained electrons, resulting in an overall positive or negative charge.

Ionic Bond

A bond formed by the strong electrostatic attraction between positive metal ions and negative non-metal ions.

Ionic Lattice

A repeating $3D$ structure of ions that forms large crystals like sodium chloride ($NaCl$).

Democritus

The first person (400 BC) to suggest everything was made from small, indestructible particles called atoms.

Sir JJ Thomson

The scientist who proposed the 'plum pudding' model and suggested atoms contained positive and negative charges.

Lord Rutherford

The scientist who discovered that atoms contain a nucleus and consist mostly of empty space.

Niels Bohr

The scientist who suggested that electrons occupy different energy levels known as orbits or shells.

Sir James Chadwick

The scientist who discovered that the nucleus contains neutrons with a neutral charge.

Molecule

A fixed group of atoms bonded together, which can be an element (like $O_2$) or a compound (like $H_2O$).

Monatomic Element

An element consisting of only a single atom, such as noble gases like Helium ($He$) and Neon ($Ne$).

Molecular Element

An element consisting of two or more of the same type of atom bonded together, such as Nitrogen ($N_2$).

Homogenous Mixture

A mixture where substances are evenly mixed together to give a uniform composition throughout, such as solutions or colloids.

Heterogeneous Mixture

A mixture where substances are unevenly mixed with visibly different states of matter, such as suspensions.

Solution

A homogenous mixture where a solute is completely dissolved in a solvent.

Solute

The substance that is dissolved into a liquid.

Solvent

The liquid that a substance dissolves into.

Alloy

A mixture of a metal with another metal or a non-metal, such as Steel ($Iron + Carbon$) or Bronze ($Copper + Tin$).

Miscible

A term describing two liquids that can mix together completely, such as water and cordial.

Malleable

A property of metals that allows them to be bent or hammered into thin sheets without breaking.

Brittle

A property of solid non-metals that causes them to shatter when bent.