Atomic Structure and Periodic Table

These flashcards cover key concepts related to atomic structure, isotopes, atomic mass, and the periodic table, helping students review important terminology and definitions.

Atomic mass

A weighted average derived from the masses and abundances of each isotope.

Isotopes

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

Mass number (A)

The total number of protons and neutrons in an atom.

Atomic number (Z)

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

Cation

An atom that has lost one or more electrons and carries a positive charge.

Anion

An atom that has gained one or more electrons and carries a negative charge.

Francis Aston and Arthur Dempster

Developed the mass spectrometer, an instrument used to determine the occurrence and natural abundances of isotopes by measuring the mass-to-charge ratio of ions.

Dmitri Mendeleev and Henry Moseley

Developed and refined the Periodic Law, which states that the properties of the elements are periodic functions of their atomic numbers.

Metals

Elements that are shiny, malleable, and good conductors of heat and electricity.

Nonmetals

Elements that typically have a dull appearance and are poor conductors of heat and electricity.

Metalloids

Elements that have properties intermediate between metals and nonmetals.

Homogeneous mixture

A mixture with a uniform composition throughout.

Heterogeneous mixture

A mixture with a non-uniform composition.

Noble gases

Elements in group 18 of the periodic table, known for their lack of chemical reactivity.

Chemical symbol

An abbreviation used to indicate an element or an atom of an element.

Chemical change

A change that results in the formation of new chemical substances.

Physical property

A characteristic that can be observed without changing the substance's chemical identity.

Chemical property

A characteristic that can only be observed during a chemical reaction.

Density

The ratio of the mass of a sample to its volume: d = \frac{m}{V}.

Significant figures

The digits in a number that contribute to its precision, including all nonzero digits and any zeros between them.

Dimensional analysis

A mathematical technique used to convert between different units of measurement.

Unified atomic mass unit (amu)

A standard unit of mass used to measure atoms and molecules, defined as \frac{1}{12} of the mass of a carbon-12 atom.

J.J. Thomson

Conducted the Cathode Ray Tube Experiment; led to the discovery of the electron and the measurement of its charge-to-mass ratio.

Ernest Rutherford

Conducted the Gold Foil Experiment; demonstrated that the atom has a tiny, dense, positively charged nucleus.

Robert Millikan

Conducted the Oil Drop Experiment; allowed for the determination of the fundamental charge of an electron.

James Chadwick

Discovered the neutron in 1932, completing the basic model of the atomic nucleus.

John Dalton

Proposed Dalton's Atomic Theory, a set of postulates stating that all matter is composed of small, indivisible particles called atoms.