U9 Matter
Aristotle
(BCE)
Democritus
(BCE)
Alchemy
Dalton
(1808)
Thompson
(1904)
Rutherford
(1910)
Bohr
(1922)
deBroglie
(1923)
Heisenberg
(1927)
What is Matter made of?
 earth, water, air, fire
 tiny indivisible, indestructible particles
 atomos = “uncuttable”
 not accepted for ~2000
years!
 combination of science and mysticism
 search for “philosopher’s stone”
 wanted to change lead into gold
 atomic theory
 tiny elastic spheres unique to each element
 combine to form other substances
 electron
 plum pudding model
 (-) electrons embedded in (+) atom
 proton
 gold foil experiment
 mostly empty space
 dense center with (+) charge
 electrons travel in specific energy levels and not
between
 electrons described as waves instead of particles
 uncertainty principle
 can’t know electron location and speed at same time
Schrodinger
(1930)
 electron probability cloud model
Chadwick
(1932)
 neutron in nucleus
Gell-Mann
 quarks: tiny particles that make up protons and neutrons
 flavors: up, down, strange, charm, bottom, top
Matter
Atom
Sub-atomic
particles
Structure
 anything that takes up space and has mass.
 smallest unit of an element that has all the properties of
that element.
proton
neutron
electron
Location
nucleus
nucleus
space outside nucleus
Charge
+1
0
-1
Mass
~1 amu
~1 amu
~1/2000 amu
 most of atom is empty space!
 Nucleus: overall (+) charge
 very small (~0.001% of atom’s volume)
 very dense (most of atom’s mass)
 analogy:
 nucleus = puck in center of hockey rink
 whole atom = entire arena and parking lot
Standard
Atomic
Notation
Element Info
on PT
 atomic number = # protons (ID of element)
 in neutral atom: # protons = # electrons
 atomic mass (amu) = # protons + # neutrons
 element name
 atomic number: # protons = # electrons
 chemical symbol
 mass: # protons + # neutrons
Changing #
subatomic
particles
 Δ # protons  different element
 C has 6p+
 add 1 proton  7p+ = N
 Δ # electrons  (+) or (-) ion of same element
 neutral Na has 11p+ / 11e loses 1e- 11p+ /10e-  Na+1
 Δ # neutrons  isotope of
same element
 12C has 6 p+ and 6 n0
 add 1 n0  13C
https://www.ted.com/talks/just_how_small_is_an_atom
https://www.youtube.com/watch?v=xazQRcSCRaY
https://www.youtube.com/watch?v=QbWKF9uDF7w
https://www.youtube.com/watch?v=IO9WS_HNmyg