Unit 4 Atomic History Flashcards
Democritus
- Proposed the idea of atoms as the smallest undividiable particle of a substance.
- Stated that all the universe is composed of two elements: the atoms and the void in which they exist
John Dalton
- Developed an “atomic theory” with spherical solid atoms based upon measurable properties of mass
- Atoms make up everything and cannot be created or destroyed.
- Atoms of an element are identical.
- Atoms are rearranged in chemical reactions to form different substances.
Sir William Crookes
- Discovered
- cathode rays travel in straight lines
- cause glass to fluoresce
- give a negative charge to objects they strike
J.J. Thomson
- Discovered/proved the electron
- Used a CRT to experimentally determine the charge to mass ratio (e/m) of an electron =1.759 x 10 8 coulombs/gram
- Also studied “canal rays” and found they were associated with the proton ( H+)
Ernest Rutherford
- Studied radiations emitted from uranium and thorium and named them alpha and beta
- Gold Foil experiement
- Using alpha particles as atomic bullets, discovered the nucleus and established that the nucleus was
- very dense
- very small
- positively charged
- Disproved the Plum Pudding Model (assumed that the electrons were located outside the nucleus)
Max Planck
- used the idea of quanta (discrete units of energy) to explain hot glowing matter
Hantaro Nagaoka
- Proposed a “Saturnian” model of the atom with flat rings of electrons revolving around a positively charged particle
R.A. Millikan
- Oil drop experiment determined the charge (e=1.602 x 10 -19 coulomb) and the mass (m = 9.11 x 10 -28 gram) of an electron.
H.G.J. Moseley
- Using x-ray tubes, determined the charges on the nuclei of most atoms
- wrote “The atomic number of an element is equal to the number of protons in the nucleus”
Niels Bohr
- Developed an explanation of atomic structure that underlies regularities of the periodic table of elements;
- Developed Bohr model (planetary model) - had atoms built up of sucessive orbital shells of electrons
- Proposed energy levels for electrons
Louis de Broglie
- Discovered that electrons had a dual nature-similar to both particles and waves (Particle/wave duality)
Werner Heisenberg
- Described atoms by means of formula connected to the frequencies of spectral lines.
- Proposed Principle of Indeterminancy (Heisenberg Uncertainty Principle) - you can not know both the position and velocity of a particle
Erwin Schrodinger
- Viewed electrons as continuous clouds
- Introduced “wave mechanics” as a mathematical model of the atom
James Chadwick
- Using alpha particles discovered the neutron
s sublevel
Has one orbital
Present on every energy level
p sublevel
3 orbitals
appears for the first time on 2nd energy level
d sublevel
5 orbitals
appears for the first time on 3rd energy level
always fills after the s on the level above (4s and then 3d)
f sublevel
7 orbitals
appears for the first time on 4th energy level
fills after the s orbital two energy levels above
(4f fills immediately after 6s)
cation
ion with a positive charge
usually a metal ion
anion
ion with a negative charge
usually a nonmetal
speed of light
3.0 x 108 m/s
Planck’s constant
6.626 x 10-34
Aufbau Principle
Electrons are added to an atom in order of increasing energy.
Hund’s Rule
One electron is added to all orbitals within a sublevel before a second electron is added to any orbital.
Pauli Exclusion Principle
Two electrons occupying the same orbital must have opposite spins.
Mass of proton
1 amu
Mass of neutron
1 amu
Mass of electron
0 amu
Charge of Proton
+1
Charge of electron
-1
Charge of neutron
0
Location of protons
Nucleus
Location of Neutrons
Nucleus
Location of Electrons
Electron cloud or Energy Levels or Orbits
Protons determine __________
identity of the element
Neutrons determine ________
which isotope of the element.
Electrons determine __________
the charge (the ion of the element)
First quantum number
(Principal quantum number)
n, describes the energy level the electron is on
Second quantum number
(angular quantum number)
Describes the shape of the orbital (s, p, d, f)
Allowed third quantum numbers for s
0
Allowed third quantum numbers for p
-1, 0, +1
Allowed third quantum numbers for d
-2, -1, 0, 1, 2
Allowed third quantum numbers for f
-3, -2, -1, 0, +1, +2, +3
Third quantum number
Describes the orientation of the orbital within the sublevel (which blank)
Second quantum number values for each sublevel
s = 0
p = 1
d = 2
f = 3
Fourth quantum number
describes spin of an electron
First electron in orbital (blank) = +1/2
Second electron in orbail (blank) = -1/2
