Download AP lesson 9 Atomic structureOK

Atomic structure
•
•
•
•
•
Sub atomic particles
Atomic number
Mass number
Atomic mass
Atomic weight
Atoms,
Molecules,
and Ions
The Nuclear Atom
According to Rutherford
• He postulated a very small, dense nucleus with the
electrons around the outside of the atom.
Difference
of 105 =
100,000
1 Å = 10-10 m
• Most of the volume of the atom is empty space.
Atoms,
Molecules,
and Ions
Subatomic Particles: Charge & Mass
• Protons were discovered by Rutherford in 1919.
• Neutrons were discovered by James Chadwick in 1932.
1 amu = 1.66054 ·10-24 g and 1 g = 6.02214 * 1023 amu
• Protons and neutrons have essentially the same mass.
Atoms,
• The mass of an electron is so small we ignore it.
Molecules,
and Ions
Elements & Atomic terminology
• Atomic number (Z) = #p
#p = #e- in a neutral atom
Identifies the element
• Mass number (A) = (#p+) + (#no)
A = Z + N
• Isotopes Atoms of the same element (same at. #), having
different number of neutrons.
• Atomic mass or weigh (a.m.u. or grams)
The average mass of the isotopes of an element,
considering their natural % abundance.
Atoms,
Molecules,
and Ions
Atomic terminology
Atoms,
Molecules,
and Ions
Learning Check
An atom of zinc has a mass number of 65.
A. What is the number of protons in the zinc atom?
30
B. What is the number of neutrons in the zinc atom?
35
C. What is the mass number of a zinc isotope
with 37 neutrons?
67
Atoms,
Molecules,
6 Ions
and
Learning Check
Atoms,
Molecules,
and Ions
Isotopes
• Atoms with the same number of protons
but different numbers of neutrons.
• Show
almost
identical
chemical
properties; chemistry of atom is due to
its electrons.
• In nature most elements contain
mixtures of isotopes.
Atoms,
Molecules,
and Ions
*
Isotopes
(atomic
number =1)
• Atoms of the same
element with different
masses (mass number)
• Isotopes have different
numbers of neutrons.
Atomic mass or weigh?
(atomic
number =2)
99.985%
0.015%
0%
Natural Abundance
0.000137%
99.999863%
Natural Abundance
(atomic
number =3)
7.59%
92.41%
Natural Abundance
Isotopes of Carbon: (isotope notation)
Mass number
Atomic number
Natural Abundance:
11
C
6
negligible
12
C
6
98.89%
13
C
6
1.11%
14
C
6
Atoms,
Molecules,
and Ions
negligible
Isotopes of Hydrogen
1H
2H
3H
99.985%
0.015%
negligible
Natural
Abundance
unstable, radioactive
Atoms,
Molecules,
and Ions
Isotopes of Carbon
12C
13C
14C
Natural
Abundance
98.89%
1.11%
negligible
Atoms,
Molecules,
and Ions
Table of Isotopes (partial)
Atoms,
Molecules,
and Ions
Determination of Atomic Mass
Mass spectrometer: can separate isotopes of an element based
on their charge and mass, & measure their % abundance.
Ionizing
chamber
Atoms,
Molecules,
and Ions
Mass Spectrometer
Mass Spectrum of
Germanium (Ge)
Atoms,
Molecules,
and Ions
Atomic Mass (Weight): the average
mass of isotopes of an element,
considering their natural abundance
*
Isotope % Abund. f.Abund. X Mass # =
3He
0.01
(0.0001 x
4He
99.99
(0.9999 x 4) = +3.9996
3) = 0.0003
4.000
35Cl
75.77
Atomic Mass (Weigh):
37Cl
24.23
AM = (f1 x M#1) + (f2 x M#2) + …
24Mg
78.99
25Mg
10.00
26Mg
11.01
Atoms,
Molecules,
and Ions
Learning Check
Atoms,
Molecules,
and Ions