Transcript Atomic Timeline

Atomic Timeline
650 BC - Greek Philosophers
Earth
Water
Wind
Fire
450 BC - Democritus
Deep Thinker - No evidence
was provided
Greek: atomus – means indivisible
Coined the term “atom”
The Dark Ages
Religious and scientific persecution
BUT only in EUROPE
Meanwhile…
Trade routes between the
Middle East and Asia kept
Science going.
Far Eastern alchemists designed
modern glassware and apparatus
1808 - Dalton
► First
model based on experiments.
1. All matter is made up of tiny particles called atoms.
They cannot be created, destroyed or divided into
smaller particles.
2. The atoms of one element cannot be converted into the
atoms of any other element.
3. All the atoms of one element have the same properties,
such as mass and size.
4. Atoms of different elements combine in specific
proportions to form compounds.
1903 – J.J. Thomson
► Introduction
of atomic charge.
Sphere of positive mass with negative
charges interspersed.
Raisin Bun model
1911 – Ernest Rutherford
► Gold
Foil Experiment
Anticipated Results
Actual Results
1911 - Rutherford
► 1.
most of the atom is empty space
► 2. there must be a central component of
the atom containing all of the positive
charge.
He called this the Nucleus
1913 – Neils Bohr
► Explained
the path of electrons (orbits)
around the positive nucleus
► These orbits are specific distances from the
nucleus
► Electron energy level model.
Modern Atomic Theory
All matter is made up of atoms. Each atom
consists of subatomic particles: electrons,
protons & neutrons (an atom is divisible, it is the
smallest part of an element)
2. Atoms of on element cannot be converted into
atoms of another element by a chemical reaction
(nuclear reactions, alter the composition of the
nucleus, so convert atoms of one element into
another)
3. All atoms have the same properties such as size
and mass. (exception is isotopes)
4. Atoms of different elements combine in fixed
proportions to form compounds. (no changes
yet)
1.
Atomic Structure
Subatomic particles
Location
Relative
Mass
Charge
Proton
Nucleus
1 amu
Positive
Neutron
Nucleus
1 amu
Neutral
Electron
Energy
Levels/
Orbitals
0.00054
amu
Negative
* 1 amu (atomic mass unit) = 1.66 X10-27 kg
Standard Atomic Notation
Mass Number (A) – Each element is assigned a mass number
which corresponds to the number of protons plus neutrons
found in the nucleus of the atom of that element.
A = #p+ + #n
Atomic Number (Z) – Each element is assigned an atomic
number which corresponds to the number of protons found in
the nucleus of the atom of that element.
Standard Atomic Notation
Mass #
Atomic #
A
Z = #p+
X
Z
28
Si
14
Gold?
p = 14
e = 14
n = 14
Isotopes
Isotopes – atoms of an element that have the same
number of protons but different numbers of
neutrons.
This change in neutrons is reflected in the Mass Number
12
C
6
Carbon -12
13
C
6
Carbon -13
14
C
6
Carbon -14
The mass listed on the Periodic Table is an average atomic
mass calculated from the masses of the naturally
occurring isotopes of that element.
Isotopes of the same type of atom exhibit the same chemical
properties!
Radioisotopes
Radioisotopes – (short for radioactive isotopes) have
unstable nuclei. Radioisotopes decay into more
stable atoms by giving off radiation.
Radioactivity – process of releasing energy
and/or particles from the nucleus of an atom as it
decays.
Applications – carbon dating, x-rays, cancer treatments…
Bohr – Rutherford Diagrams