Chapter 2: Atoms, Molecules, and Ions

Who first tries to explain why chemical changes occur?

The Greeks

Who used the term "atomos" to describe atoms?

Leucippos

Who supported the theory that matter was made up of small, indivisible particles?

Demokritos of Abdera

Who laid the foundations of modern chemistry with the development of systemic metallurgy?

German, Georg Bauer

Who laid the foundations of modern chemistry with the medicinal application of minerals?

Swiss alchemist/physician, Paracelsus

Who was the first chemist to preform truly quantitative experiments?

Robert Boyle

Who invented Phlogiston (substance that flowed out of burning material)?

Georg Stahl (German)

Who discovered oxygen gas?

Joseph Priestley (English clergyman and scientist)

"Father of Modern Chemistry"

Antoine Lavoisier (French Chemist)

Discovered that oxygen was involved in combustion

Antoine Lavoisier (French Chemist)

Verified the law of conservation of mass

Antoine Lavoisier (French Chemist)

Died during the French Revolution.

Antoine Lavoisier (French Chemist)

Responsible for the Law of Definite Proportion

Joseph Proust (French)

Law of Definite Proportion

A given compound always contains exactly the same proportion of elements by mass.

Law of Conservation of Mass

Mass is neither created nor destroyed in a chemical reaction

Proposed that given a certain element/compound, it will always contain the same combination of atoms.

John Dalton (English)

Discovered the Law of Multiple Proportions.

John Dalton (English)

Law of Multiple Proportions

When two elements form a series of compounds, the ratios of the masses of the second element that combine with 1g of the first element can always be reduced to small whole numbers.

Published the following atomic theory:

1. Each element is made up of tiny particles called atoms.

2. The atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways.

3. Chemical compounds are formed when atoms of different elements combine with each other. A given compound always has the same relative numbers and types of atoms.

4. Chemical reactions involve reorganization of the atoms—changes in the way they are bound together. The atoms themselves are not changed in a chemical reaction.

John Dalton (English)

Discovered that water is made of two parts hydrogen gas, one part oxygen gas.

Joseph Louis Gay-Lussac

Discovered the elements cerium, thorium, selenium, and silicon

Jöns Jakob Berzelius (Swedish)

Invented a simple set of symbols for the elements along with a system for writing the formulas of compounds.

Jöns Jakob Berzelius (Swedish)

Proposed that at the same temperature and pressure, equal volumes of different gases contain the same number of particles

Lorenzo Romano Amedeo Carlo Avogadro (Italian)

Avogadro's Hypothesis

At the same temperature and pressure, equal volumes of different gases contain the same number of particles.

Performed experiments with cathode ray tubes, postulated that the stream produced was negatively charged particles.

J. J. Thomson

Determined the charge-to-mass ratio of an electron.

J. J. Thomson

Postulated the Plum Pudding Model of the Atom

J. J. Thomson

Model that postulated that an atom consisted of a diffuse cloud of positive charge with the negative electrons embedded randomly in it.

Plum Pudding Model

Performed experiments involving charged oil drops

Robert Millikan

Calculated the mass of the electron

Robert Millikan

gamma (γ) rays

high-energy "light"

beta (β) particles

high-speed electrons

alpha (α) particles

consist of two protons and two neutrons bound together into a particle identical to the nucleus of a helium-4 atom, 7300 times the mass of an electron

Performed experiments with gold foil to test the plum pudding model of the atom.

Ernest Rutherford (New Zealander)

Scientist who did much early work in characterizing radioactivity.

Ernest Rutherford (New Zealander)

Gold Foil Experiment

Conducted by Ernest Rutherford in which alpha particles that were shot at gold foil were deflected when they hit the positive center of gold atoms. The nucleus was discovered as a result of this experiment.

Proposed the theory of a nuclear atom.

Ernest Rutherford (New Zealander)