Understanding Atomic Structure and Key Experiments

A collection of flashcards based on key concepts and vocabulary from a lecture about atomic structure and historical experiments in chemistry.

Postulate

A statement or idea that is assumed to be true for the sake of argument or investigation.

Atomic Theory

A scientific theory that matter is composed of discrete units called atoms.

Law of Constant Composition

A chemical law stating that a given compound always contains the same proportion of elements by mass.

Law of Multiple Proportions

A law stating that when two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other are in a ratio of small whole numbers.

Law of Conservation of Mass

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

Cathode Ray Tube

An experimental apparatus used in early investigations of the atom, demonstrating the existence of electrons.

Plum Pudding Model

J.J. Thomson's model of the atom where electrons are embedded in a positively charged 'soup'.

Millikan's Oil Drop Experiment

An experiment that measured the charge of the electron using charged oil droplets suspended in an electric field.

Rutherford's Gold Foil Experiment

An experiment that demonstrated the presence of a dense nucleus in an atom by observing the deflection of alpha particles.

Isotope

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

Atomic Number

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

Atomic Mass

The weighted average mass of an element's isotopes, typically expressed in atomic mass units (amu).

Electron

A negatively charged subatomic particle found in the outer regions of an atom.

Proton

A positively charged subatomic particle found in the nucleus of an atom.

Neutron

A neutral subatomic particle found in the nucleus of an atom.

Mass Number

The total number of protons and neutrons in an atomic nucleus.

Atomic Weight

The average mass of an atom of an element based on the relative abundances of its isotopes and expressed in atomic mass units.

Electrostatic Force

The attraction or repulsion between charged particles.

Charge to Mass Ratio

The ratio of the charge of a particle to its mass, often calculated in experiments involving charged particles.

Chemical Reaction

A process that leads to the transformation of one set of chemical substances to another.

Aerosol

A suspension of fine solid particles or liquid droplets in air or another gas.

Hydrogen Atom

The simplest atom consisting of one proton and one electron.