Chemistry: Atoms, Elements, Compounds and Chemical Reactions

Flashcards covering key terms and definitions related to atoms, elements, compounds, reactions, and fundamental principles in chemistry.

Atom

The smallest part of an element that can exist.

Compound

A substance formed from two or more elements chemically combined in fixed proportions.

Mixture

A combination of two or more substances that are not chemically bonded, maintaining their individual properties.

Mendeleev's Periodic Table

An early version of the periodic table where elements were arranged by atomic mass and gaps were left for undiscovered elements.

Ionic Bonding

A type of bond formed when electrons are transferred from a metal atom to a non-metal atom, resulting in oppositely charged ions.

Covalent Bonding

A type of bond where atoms share pairs of electrons.

Metallic Bonding

Bonding that occurs in metals, characterized by a sea of delocalized electrons surrounding positive metal ions.

Exothermic Reaction

A chemical reaction that releases energy into the surroundings, causing a temperature increase.

Endothermic Reaction

A chemical reaction that absorbs energy from the surroundings, resulting in a temperature decrease.

Law of Conservation of Mass

A principle stating that mass is neither created nor destroyed in a chemical reaction; the mass of reactants equals the mass of products.

Relative Atomic Mass

An average value reflecting the isotopic composition of an element, considering the abundance of each isotope.

Isotope

Atoms of the same element with different numbers of neutrons.

pH Scale

A scale measuring the acidity or alkalinity of a solution, ranging from 0 (acidic) to 14 (alkaline), with 7 being neutral.

Electrolysis

The process of breaking down an ionic compound into its elements using an electrical current.

Alkali Metals

Group 1 elements that are highly reactive with water, forming alkaline solutions.

Halogens

Group 7 non-metal elements, known for forming salts with metals and featuring seven electrons in their outer shell.

Noble Gases

Group 0 elements with full outer electron shells, making them generally unreactive.

Avogadro's Constant

The number of particles in one mole of a substance, approximately 6.02 x 10^23.

Limiting Reactant

The reactant that is fully consumed in a chemical reaction, limiting the amount of product formed.

Catalyst

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

Reversible Reaction

A reaction where the products can reform the original reactants under suitable conditions.