Atomos - Chino Valley Unified School District · s orbital (1) can hold a max of 2 electrons p...
Transcript of Atomos - Chino Valley Unified School District · s orbital (1) can hold a max of 2 electrons p...
History of the atom (atomic theory)
Greeks:
Democritus (~400 BC); strictly philosophy
World made of two things:
Empty space and tiny particles
The word atom comes from the Greek word:
Atomos
To not cut (indivisible)
The smallest bit of matter that could be conceived
Contradicted Aristotle until Dalton
Alchemist
First to study matter using a laboratory
Main work was to try and change matter from one form to another
Transmutation
Pb → Au
Lead into Gold
John Dalton
Early 1800’s
Father of Atomic Theory
Used quantitative measurements
Explained how matter links together in definite proportions (worked with gases)
His proportions were based on MASS
Worked with water “molecules”
Ratios:
Mass- 8 O to 1 H
Atoms- 2 H to 1 O per molecule
Volume- 2 H to 1 O
2 H2O → 2 H2 ↑ + O2 ↑
Coined the terms:
Monatomic molecule (H)
Diatomic molecule (H2)
Chemical bonds
JJ Thompson
Late 1800’s
Discovered the electron and the proton
Subatomic particles
Atom made of negative particles mixed equally in a sphere of positive material
Plum pudding model
Ernest Rutherford
1912- 1919
Atoms have a small center
Occupies ~ 10-12 % of the atoms volume
The center has a positive charge (+); nucleus
Mass of the atom is concentrated in its nucleus
# of electrons MUST = # of protons
Electrically neutral
Evidence for protons in the nucleus movie
Nagaoka model
Electrons revolving around the nucleus like the planets around the sun
Neils Bohr
~ 1913
Used quantum mechanics
Electrons found in “shells” or energy levels
1st shell can hold 2 electrons
2nd shell can hold 8 electrons
Successive shells can hold more electrons
Maximum of 7 shells
Octet rule
http://jersey.uoregon.edu/vlab/elements/Elements.html
Schrodinger model (Wave model)~1929
Current model (Quarks; superstring theory ?)Abandoned the idea of precise orbits for electronsPauli exclusion principleHeisenberg uncertainty principle“spdf” model
Describes the regions of space where electrons are most likely to be found
Based on work by Louis de Broglie
Atoms are 99.9999999 % empty space
Protons and neutrons are held together in the nucleus by the strong force
The weak force accounts for radioactivity
Very important
Electrons orbit the nucleus at different energy levels
Within each energy level you can have orbitals
s orbital (1) can hold a max of 2 electrons
p orbital (3) can hold a max of 6 electrons
d orbital (5) can hold a max of 10 electrons
f orbital (7) can hold a max of 14 electrons
Electrons are found in orbitals within energy levels
s orbital p orbital
d orbital (x-y) d orbital (z)
Pauli exclusion principle
Only 2 electrons per orbital
# of electrons in the outer most energy level determines how the atom react with other atoms; ∴ the properties of that atom
These electrons have a name:
Valence electrons
Walter Bothe and Sir James Chadwick
1930- 1932
Discovered the neutron
Same mass as the proton BUT no charge
Atomic structure
A. Quarks
Hypothetical particles (smallest form of matter)
Proposed in 1963 (Gell- Mann and Zweig)Quarks have fractional chargesCome in six flavorsGrouped together in threes to form almost all subatomic particles
Experimental evidence exist to show ALL six flavors exist
Each quark has an antiquark; antimatter
Gluon is the force that holds quarks together
B. Subatomic particles (3 types)
1. Proton (+ charge; has mass)
2. Neutron (no charge; has mass)
3. Electron (- charge; has mass BUT very little)
1 and 2 found in the atomic nucleus AND
Accounts for ALL of the atom’s mass
Atomic Terms
A. Atomic Number
Total # of protons in the nucleus
Total # of electrons
Name of the atom (element)
# of protons = # of electrons
B. Atomic Mass Number
# of protons + # of neutrons in the nucleus of the atomIn the periodic table atomic mass number that we see is an average of all the different types of isotopes for that atom (this is why the atomic mass number is not even)
To find the # of neutrons in a atom:
# of neutrons = Atomic Mass # - Atomic #
C. Isotopes
The name, of the atom, remains the same.
Has the same number of protons and electrons.
Has a different number of neutrons.
Some isotopes are radioactive (Radioisotopes)
α β γ emitters
D. Ions
Same number of protons/ neutrons
Different number of electrons (add or remove)
Ions have a “net charge” (either + or -)
Not very stable
• One fact we know… is that atoms are very, very old.
• All the atoms, on the Earth, are older than the sun and Earth.
• All of the subatomic particles in your body have existed since the beginning of time.
The Ultimate Recycling
Atoms – How Old Are You???
Program
• Scottish botanist, Robert Brown- noticed that the grains of pollen under his microscope were continually moving while suspended in the water mount.
- now called “brownian motion”, the collision of visible particles and invisible atoms.
Atoms - Visual Evidence in 1827
• Hydrogen was the first element to form in the universe.
• Today, H2 accounts for 90% of all elements.
• All other elements are heavier than H2. These other elements were probably manufactured in stars that have exploded and have formed our solar system. Super nova
B. General Information