Discovery of electrons, proton, and neutrons

Bata (b)

+

Alpha (a)

-

Thomson charge/mass of e- was

-1.76 x 10^8

Rutherford found

1. Atoms positive charge is in nucleus 2. Proton has opposite charge of electron 3. Mass of proton is 1840 x mass of e-

John Dalton Atomic Theory (1808)

1. Elements are composed of extremely small partciles called atoms, all atoms of a given element are identical(not true) 2. Compounds are composed of atoms of more than one elememt 3. Chemical reactions can only involve the rearangement of atoms. Atoms are not created or destroyed in chemical reactions

E-

=-1.6 x 10^-19

Daltons atomic theory (law of conservation mass)

Atom of element x+ atoms of element y (16x + 8y =8x^2y)

JJ Thomson used a

Cathode ray tube that made the element glow and it attracted or repelled to a magnet, then a paddle moved and they could tell which is was attracted to, it was lighter than He (discovered electron, first discovered subatomic particle and found weight)(won Nobel prize)

Chadwick's Experiment 1932

H atom = 1 proton, etc, mass of he/mass of h=4 but should be 2, found neutron is neutral charge -e + p = m (mass)

Low of multiple proportions

Have to be whole number ratios, never less than a whole atom

jj thomson discovered

Measured mass/charge of e-

Millikan's Oil Drop Experiment 1909

Measured the mass of e-, charged them to known level of electron, dropped them and it would repel or fall against negative plate, found mass of e-, radioactive substance ha store rays (a,b,c)

Gama (c)

Neutral

Atomic Number (Z)

Number of protons

Mass number (a)

Number of protons + neutrons

Rutherford Experiment Design

Shot alpha particles at gold foil, 180 per minute, rotated it to find distribution of reflection, alpha particles hit positive charge and every once and a while hit in center which meant there was a nucleus

"If the atoms is the Houston Astro dome,

Then the nucleus is a marble on the 50 yd line"

Earnest Rutherford proved this wrong

Thomson said atoms had positive charge spread over entire sober to even out like pudding, idea stuck for 10 years

Isotopes are

atoms of the same element with different numbers of neutrons in the nuclei