Ch 2 Study Notes on Atoms and Elements

Flashcards covering key concepts related to atoms and elements, including atomic theory, structures, and properties.

Antoine Lavoisier

Referred to as the father of modern chemistry; established that mass is conserved in chemical reactions.

Law of conservation of mass

Total mass of reactants equals total mass of products in a chemical reaction.

Joseph Proust

Proposed the law of definite proportions, which states a given compound always contains the same proportion of elements by mass.

Law of definite proportions

All samples of a given compound have the same proportions of constituent elements.

Dalton's Atomic Theory

A theory proposing that each element consists of indivisible atoms, and that atoms of one element differ from those of all other elements.

Law of multiple proportions

When two elements form different compounds, the masses of one element that combine with a fixed mass of the other can be expressed as a ratio of small whole numbers.

J.J. Thomson

Discovered the electron and proposed the plum pudding model of atomic structure.

Plum pudding model

An early model of the atomic structure where electrons are embedded in a positively charged cloud.

Robert Millikan

Determined the charge of the electron through his oil drop experiments.

Ernest Rutherford

Discovered the atomic nucleus and proposed that the atom is mostly empty space with a dense, positively charged nucleus.

Alpha particles

Positively charged particles used by Rutherford in his experiments to probe atomic structure.

Beta particles

Negatively charged particles, essentially electrons, identified in Rutherford's experiments.

Mass number (A)

The total number of protons and neutrons in an atom's nucleus.

Atomic number (Z)

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

Isotopes

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Ion

A charged atom that results from losing or gaining electrons.

Avogadro's number

6.022140857 × 10^23; the number of atoms, molecules, or other particles in one mole of a substance.

Mole

The SI unit for the amount of substance; defined as the amount containing the same number of elementary particles as there are in 12g of carbon-12.

Molar mass

The mass of one mole of a substance, typically expressed in g/mol.

Atomic mass unit (u)

A unit of mass used to express atomic and molecular weights; defined as one-twelfth the mass of a carbon-12 atom.

Molecular mass

The sum of the atomic masses of all atoms in a molecule.

Compounds

Substances formed when two or more elements are chemically bonded together.

Periodic table

A tabular arrangement of chemical elements, organized by increasing atomic number and grouped by similar properties.

Groups (or families)

Vertical columns in the periodic table containing elements with similar chemical properties.

Periods

Horizontal rows in the periodic table where elements show a gradual change in properties.

Metals

Elements characterized by high electrical conductivity, malleability, and ductility.

Non-metals

Elements that are generally poor conductors of heat and electricity and are often brittle.

Metalloids

Elements with properties intermediate between metals and non-metals.

Significant figures

The digits in a number that are important for accuracy; includes all known digits plus one estimated digit.

Chemical equation

A symbolic representation of a chemical reaction, showing the reactants and products.

Stoichiometry

The calculation of reactants and products in chemical reactions based on the conservation of mass.