Chem Lecture 9/10/26

Atom (Dalton's Definition)

The smallest unit of an element that can participate in a chemical change.

Dalton's Second Postulate

An element is defined as a substance consisting of only one type of atom, with its mass determining its identity.

Charge

A fundamental property of subatomic particles that causes them to exert and experience forces from other charged particles.

Coulomb's Law

A mathematical relationship stating that the magnitude of electrostatic force between two charged particles is proportional to the product of the magnitudes of their charges and inversely proportional to the square of the distance between them.

Coulomb Constant ($k$)

The constant in Coulomb's law equation, given as $8.99 \times 10^9$\,N\,m$^2$/C$^2$.

Cathode Ray Experiment

An experiment performed by J. J. Thomson using high potentials across metal electrodes to produce deflected particle streams, proving the existence of negatively charged subatomic particles.

Charge-to-Mass Ratio

The ratio of electric charge to mass for a particle; J. J. Thomson found this value was identical for cathode rays regardless of the metal used, proving electrons are a fundamental subatomic constituent of all atoms.

Oil Drop Experiment

An experiment conducted by Robert A. Millikan that determined the elementary charge of an electron by balancing gravitational and electrostatic forces on charged oil droplets.

Electron

A fundamental subatomic particle located outside the nucleus carrying a negative charge of $1.6 \times 10^{-19}$\,C and a mass of approximately $9.1 \times 10^{-31}$\,kg.

Gold Foil Experiment

An experiment by Ernest Rutherford shooting alpha particles at thin gold foil, revealing that atoms consist primarily of empty space with a small, dense central nucleus.

Alpha Particles