Atoms and Molecules Overview

Mass is neither created nor destroyed in a chemical reaction.

A process where substances rearrange to form new substances.

Elements combine in fixed ratios by mass in a chemical compound.

Fundamental substances that cannot be broken down further.

Substances formed by the chemical combination of two or more elements.

Scientist who established laws of chemical combination

Scientist who proposed the atomic theory.

Theory proposing that matter is made up of tiny, indivisible particles called atoms.

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

Tiny particles that make up all matter (elements, compounds, and mixtures).

Atoms cannot be created or destroyed in a chemical reaction.

Water always contains hydrogen and oxygen in a 1:8 mass ratio, regardless of the source.

Elements in a compound combine in fixed proportions by mass.

Ammonia has nitrogen and hydrogen in a 14:3 mass ratio.

Six statements that describe the basic ideas behind Dalton's atomic theory.

A group of two or more atoms bonded together, forming a distinct unit.

The number of atoms present in a molecule of an element.

An element that exists as single atoms.

An element that exists as two atoms bonded together.

An element that exists as more than two atoms bonded together.

A compound formed by the electrostatic attraction between oppositely charged ions.

A negatively charged ion.

A positively charged ion.

A unit of mass defined as 1/12th the mass of a carbon-12 atom. It is used to express the masses of atoms and molecules.

The current standard unit for atomic mass, replacing the older ‘amu’. It is equal to the mass of one atom of carbon-12.

A one or two-letter abbreviation that represents an element. The first letter is always capitalized.

A compound formed by the chemical combination of carbon and oxygen in a fixed ratio of 3 g carbon to 4 g oxygen.

If we define the atomic mass unit as the mass of one carbon atom, then the atomic mass of carbon is 1.0 u.

In the CO molecule, the atomic mass of oxygen would be 1.33 u, assuming carbon's atomic mass is 1 u.

It is convenient to express atomic masses as whole numbers or nearly whole numbers to simplify calculations and comparisons.

Elements are pure substances that cannot be broken down further. They have unique names and chemical symbols.

The mass of one mole of atoms of an element expressed in grams. It is numerically equal to the atomic mass in atomic mass units (u).

The mass of one mole of a substance (atom or molecule) expressed in grams. For a molecule, it's numerically equal to the molecular mass in atomic mass units (u)

A unit of amount of substance. One mole contains 6.022 × 10^23 particles (atoms or molecules).

The number of particles (atoms or molecules) in one mole of a substance, equal to 6.022 × 10^23

The sum of atomic masses of all atoms in a formula unit of a compound. It's calculated like molecular mass but used for ionic compounds.

The smallest unit of an ionic compound that represents its composition.

The formula unit mass of NaCl is 58.5 u. It is calculated by adding the atomic masses of sodium (Na) and chlorine (Cl): 23 u + 35.5 u = 58.5 u.

A way to express the quantity of a substance in terms of the number of its molecules or atoms, rather than their masses. It allows us to understand the ratios of reactants and products in a chemical reaction.

This equation shows that two molecules of hydrogen (2H2) react with one molecule of oxygen (O2) to produce two molecules of water (2H2O). This illustrates the mole concept, where the coefficients represent the relative number of molecules involved in the reaction.

The mole concept helps us understand the proportions of reactants and products in a chemical reaction. It allows us to predict how much of a product will be formed based on the amount of reactants used.

Molecular mass refers to the mass of a molecule, which is a neutral group of atoms held together by covalent bonds. Formula unit mass refers to the mass of a formula unit, which is the smallest unit of an ionic compound, consisting of ions held together by electrostatic forces.

The mole concept provides a direct measure of the number of molecules or atoms involved in a chemical reaction. This makes it easier to understand the stoichiometry of the reaction and predict the amounts of products formed.