Chemistry | Test 1 and Exam 1 - Definitions

Element

A pure substance made of only one type of atom

Metal

An element that is usually shiny, conducts electricity, and can be shaped.

Atom

Building blocks of all matter. The smallest unit of an elements that keeps its chemical properties.

Atomic number

The number of protons in an atom: it identifies the element.

Mass number

The total number of protons and neutrons in an atom

Electron configuration

The arrangement of electrons in the shells of an atom

Electrically neutral

Having no overall charge because the number of protons equals the number of electrons

Ion

An atomic or group of atoms with an electrical charge due to gaining or losing electrons

Valency

The number of electrons an atom can gain, lose, or share when bonding to achieve a stable, full outer shell

Nucleus

The central part of an atom that contains protons and neutrons

Electron

A negatively charged particle that moves around the nucleus in shells

Proton

A positively charged particle found in the nucleus of an atom

Neutron

A particle with no charge found in the nucleus of an atom

Isotopes

Atoms of the same element within the same number of protons but different number of neutrons

Period

A horizontal row in the periodic table

Group

A vertical column in the periodic table; elements in a group have similar properties

Electron shell

An energy level around the nucleus where electrons are found

Polyatomic

Made up of more than one atom

Monoatomic

Made up of a single atom

Compound

A substance formed when two or more different elements are chemically bonded

Ionic compound

A compound formed when electrons are transferred between atoms, creating ions

Covalent

A type of bonding where atoms share electrons

Molecule

• two or more atoms joined together

• the atoms can either be the same or different

Lattice

A repeating three-dimensional structure of ions in an ionic compound

Chemical property

A property that describes how a substance reacts to form new substances

Soluble

Able to dissolve in a particular solvent (usually water)

Insoluble

Not able to dissolve in a particular solvent

Precipitate

The insoluble solid substance that forms and separates from a liquid solution.

Precipitation reaction

A reaction where a solid precipitate forms from two aqueous solutions

pH

A scale from 0-14 that measures how acidic or basic a solution is

Acid

A substance that produces hydrogen ions (H+) in water

Base

A substance that produces hydroxide ions (OH-) in water or accepts hydrogen ions. Can neutralise an acid

Indicator

A substance that changes colour depending on the pH of the solution it is mixed with, allowing for the detection of acidic or base/alkaline conditions.

Litmus paper

An indicator that turns red in acids and blue in bases

Universal indicator

An indicator that shows a range of colours to indicate pH value - how acidic or basic a solution is on a scale from 0 to 14

Neutralisation

A chemical reaction where an acid and a base react to cancel each other out, produces salt and water

Salt

an ionic compound formed from the neutralisation reaction of an acid and a base.

Mole

A unit used to measure the amount of a substance

Molar mass

The mass of one mole of a substance, measure in g/mol

Mole ratio

The ratio of moles of substances in a balanced chemical equation

Collision theory

States that chemical reactions occur only when reactant particles (atoms, ions, or molecules) collide with sufficient activation energy to break bonds and in the correct orientation

Concentration

The amount of solute dissolved in a given volume of solution; higher concentration increases reaction rate

Surface area

The total area of exposed solid; larger surface area increases reaction rate

Temperature

A measure of how hot or cold something is; higher temperature increase reaction rate

Catalyst

A substance that speeds up the rate of a chemical reaction without being consumed in the process