atoms 2 14-2011
DESCRIPTION
atoms - chm 131 spring 2011TRANSCRIPT
Law of constant
Composition
Law of multiple
John Dalton – 1803
Based on the way that elements combined in compounds.
Concluded that atoms were the smallest particles of
matter
This view had been expressed by Greek philosophers
at least 2000 years earlierLaw of multiple
proportionsat least 2000 years earlier
Dalton was the first to find EXPERIMENTAL evidence
for this belief
Postulates of Dalton’s atomic theory
• Matter made of discrete particles called atoms– An atom is the smallest particle of matter*
• Atoms of a given element are identical to other atoms of that element and different from atoms of other elements*
• Atoms of different elements combine together to form compounds compounds – A given compound will have the same number and same type of
elements
• Chemical rx involves rearrangement, separation or combinations of atoms
• Atoms are not created or destroyed*
Changes
• Matter made of discrete particles called atoms
– An atom is the smallest particle of matter*
• Atoms have subatomic particles (p+, e-, n)
• Atoms of a given element are identical to • Atoms of a given element are identical to other atoms of that element and different from atoms of other elements*
– Isotopes
• Atoms are not created or destroyed*
– E=mc2 conversion between mass and energy
demo
amu or dalton = 1/12 of C-12 nucleus
6 p + 6 n
6 X 1023 atoms 12C = 12 g
Table 3.8
Pg 97
Pg 98-103
Pg 100
ions
• Neutral atoms: #p+ = # e-
• Ions – gain or lose of electrons
– Protons are not gained/lost in normal
chemical/physical changeschemical/physical changes
• Gain e, charge…… _____ion
• Lose e-, charge ….. _____ion
We’ll look later at typical charges
For ions
Name # p+ # e- # n Mass # symbol
1 0 0
8135 Br-1
9 10 19
2 0 1
39 K+1
Ions # p+ ≠ # e-
3919 K+1
24 15
Mass # = p + n
Charge = p - e