1Democritus (460-370 BC)
- “atomos”
- aka “discontinuous matter”
2“there can be no ultimately indivisible particles
Plato and Aristotle
3Elements are composed of extremely
small particles, called atoms.
Dalton’s Atomic Theory
4All atoms of a given element are
identical, having the same size, mass,
and chemical properties. The atoms of
one element are different from the atoms
of all other elements.
Dalton’s Atomic Theory
5Who discovered electrons?
Joseph John Thompson
6Was the first component of the atom to be
Electron
7What is the mass of electron?
9.109 x 10-31 kg
8One of the components of a nucleus
Protons
9Charge of electron
-1.602 x 10-19 coulombs
10Who discovered protons?
Eugene Goldstein
11Mass of protons
1.673 x 10-27 kg
12Charge of protons
+1.602 x 10-19 coulombs
13Another component of a nucleus
Neutrons
14Who discovered neutrons?
James Chadwick in 1932
15Mass of neutrons
1.675 x 10-27 kg
16Does neutrons have charge?
They don't have charge
17number of () in the nucleus of an atom
of an element, also the number of ()
in an atom
protons and electrons
18This quantity is fundamental to the identity of
each element because it is related to the
electrical make-up of atom
Atomic number
19This quantity is fundamental to the identity of
each element because it is related to the
electrical make-up of atom, therefore:
Atomic # = # of protons = # of electrons
20total number of protons and neutrons on the
nucleus of nucleons
Mass number
21total number of protons and neutrons on the
nucleus of nucleons, therefore:
mass # = # of protons + # of neutrons
22atoms of the same element with the same
atomic number, but different mass numbers.
Isotopes
23they have the same number of
protons and electrons but different number of
neutrons.
Isotopes