Download atoms, molecules, and matter (2)

ELEMENTS – Greek theory of physical world.
All earthly objects are a mixture of:
1. EARTH (bottom – center of universe)
2. WATER (water covers earth)
3. AIR (air over water)
4. FIRE (highest – at top)
5. Ether = QUINTESSENCE (Latin) –
substance whose natural motion is that
most symmetrical and eternal of all
conceivable motion = endless circles
ATOMIMC STRUCTURE
• ATOMS – not ‘indivisible’ particles of Democritus
and Dalton, but have electrons, protons, and
neutrons.
• Solar system model – central core (nucleus) with
orbiting models
• Scale
• Atomic (Proton) Number = to the number of
protons in nucleus. This number determines
chemical species.
• Ion – atom with net electrical charge due to
loss/gain of one or more electrons
• Isotopes – same atomic number, but different
number of neutrons
ELEMENTS & THE PERIODIC TABLE
• Alchemy – develop
substance to restore
youth; turn base metal
into gold
• Origin of some chemical
symbols (Latin) →
ELEMENT
SYMBOL
ORIGIN OF SYMBOL
Copper
Cu
Cuprum (cyprus, source of copper)
Gold
Au
Aurum ('shining dawn"
Iron
Fe
Ferrum
Lead
Pb
Plumbum ("heavy")
Mercury
Hg
Hydrargyrum ("liquid silver")
Silver
Ag
Argentum
ELEMENTS – 92 natural elements
MOLECULES – collection of atoms held by chemical
bond
ex. H20 – water – 3 atoms
C6H12O6 – glucose – 24 atoms
C2H5OH – alcohol – 9 atoms
Chemical Bonding – involves electrons
A. Ionic – transfer of electrons
ex. NaCl (salt) : Na (ignites in air) Cl (poison gas)
extra Na electron fills in outer Cl shell
B. Covalent – mutual sharing of electrons
ex. H20 electrons most of the time of O leaving the
two hydrogens positive.
States of Matter
1. Solid – definite shape, atoms locked into
position, most have regular pattern.
2. Liquid – atoms packed tightly but not as
tight as to prohibit movement; has
surface.
3. Gas – large distances between
atoms/molecules
4. Plasma – completely ionized gas
‘Atomic Theory’ – explains many things
ex. Odors and evaporation
Aristotle (384-322 B.C.)
• Greek philosopher, educator, scientist
• Student of Plato
Antiparticles and Antimatter
Electron - Positron Pair (1932)
Proton - Antiproton (same mass, opposite charge)
2
Creation vs Annihilation E = mc
8
(c = speed of light : 3 x 10 m/s)