Chapter 2: Atoms, Molecules, and Ions Flashcards
First chemist
Robert Boyle
Law of conservation of mass (by whom?)
Mass is neither created nor destroyed in a chemical reaction. (by Lavoisier)
Law of definite proportion (by whom?)
A given compound always contains exactly the same proportion of elements by mass. (by Proust)
Law of multiple proportions (by whom?)
When two elements form a series of compounds, the ratios of the masses of the second element that combine with 1 g of the first element can always be reduced to small whole numbers. (by Dalton)
Avogadro’s hypothesis
At the same temperature and pressure, equal volumes of different gases contain the same number of particles.
Dalton’s Atomic Theory (1808)
- Each element is made up of tiny particles called atoms.
- The atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways.
- 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.
- 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.
J.J. Thomson (1898-1903)
Discovered electrons in the cathode ray experiment, meaning atoms have a balance of positive particles that balance exactly the negative particles
Robert Millikan (1909)
Conducted the oil drop experiment, measured the charge of an electron, calculated the mass of an electron
Henri Becquerel (1896)
Discovered radioactivity with gamma rays (high energy light), beta particles (high speed electrons), alpha particles (2+ charge)
Ernest Rutherford (1911)
Alpha particle scattering experiment, discovered the nucleus, formulated the nuclear atom
Outside the nucleus; negatively charged
Electron
In the nucleus; positively charged
Proton
In the nucleus; no charge
Neutron
Nucleus
The dense center of the atom with a positive charge that accounts for almost all of the atom’s mass
Isotopes
Atoms with the same number of protons but different numbers of neutrons
