Download Unit 3 Atomic Structure

Chemistry I Chapter 3
Introduction to Atoms
How small is an atom?
• http://micro.magnet.fsu.edu/primer/java/sci
enceopticsu/powersof10/
Atoms
Atoms vs. Hyle
• Atom - the smallest particle of an element. It
can exist alone, or combined with other atoms.
• Atoms were first suggested by Democritus
(Greek philosopher, 400B.C.).
• People that supported Democritus view were
called “Atomists”.
• Aristotle(300B.C.) did not support the idea of
atoms. He believed that all matter was a
continuous substance called hyle. Hyle was
composed of: earth, air, fire and water.
Democritus vs. Aristotle
John Dalton….THE MAN!
• John Dalton-(English school teacher) first
to explain the existence of atoms and
disspelling Aristotle’s theory of matter.
John Dalton
•
Formulates Atomic Theory:
1)
Each element is made up of tiny indivisible particles
called atoms.
The atoms of a given element are identical, atoms of
different elements are different.
Chemical compounds are formed when atoms come
together, in simple whole number ratios.
Chemical reactions involve the reorganization of the
atoms; combined, separated or rearranged.
2)
3)
4)
1903: J.J. THOMSON
• Discovers the
electron, using his
famous Cathode Ray
Tube (CRT), which
turns out to be a
primitive TV or
computer monitor.
Discovery of the Electron
In 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a
negatively charged particle, the electron.
Cathode ray tubes pass electricity through a gas that is contained at a
very low pressure.
CRT and TV
1911 Ernest Rutherford
• Rutherford discovers
the nucleus of an
atom, using his
famous gold foil
experiment.
Rutherford’s Gold Foil Experiment
Rutherford’s Gold Foil Experiment
Rutherford’s Gold Foil
Experiment
 Alpha () particles are helium nuclei
 Particles were fired at a thin sheet of gold foil
 Particle hits on the detecting screen (film) are recorded
Rutherford’s Gold Foil Experiment
How big is an atom?
Characteristics of sub-atomic
particles
Particle
Proton
Neutron
Electron
symbol charge
p+
+1
no
0
e-1
location
mass
nucleus
1 amu
nucleus
1 amu
orbital
1/1840 amu
amu = atomic mass unit, unit used to mass very
small objects. (1 amu = 1/12 the mass of a
carbon-12 nucleus)
Orbital – the 3-dimensional space around the
nucleus of an atom, where electrons are found
most of the time.
Atomic Structure
Atomic Models
• JJ Thomson model(Plum pudding model)
electrons are scattered throughout the atom,
like raisins in plum pudding.
• Rutherford Model-The atom has a central
dense core, but is mostly empty space.
• Bohr Model(Planetary model)Electrons orbit the
nucleus in circular paths, called energy levels
• Quantum Model (Modern, Shrodinger model)Electrons move randomly in spaces called
orbitals, around the nucleus.
Thomson’s Atomic Model
Thomson believed that the electrons were like plums
embedded in a positively charged “pudding,” thus it
was called the “plum pudding” model.
Rutherford’s Findings
 Most of the particles passed right through
 A few particles were deflected
 VERY FEW were greatly deflected
“Like howitzer shells bouncing off of tissue paper!”
Conclusions:
 The nucleus is small
 The nucleus is dense
 The nucleus is positively charged
The Bohr Model of the Atom
I pictured electrons
orbiting the nucleus much
like planets orbiting the
sun.
But I was wrong! They’re
more like bees around a
hive.
Neils Bohr
Quantum Mechanical
Model of the Atom
Mathematical laws can identify the
regions outside of the nucleus where
electrons are most likely to be found.
Important definitions about atoms:
atomic number = number of protons in the
nucleus of an atom. The number of protons
determines the element of an atom.
atomic mass number = mass of the atom in amu,
it includes the number of protons and neutrons.
(electrons are not counted)
Isotopes = atoms of the same element, with a
different number of neutrons in the nucleus.
Isotopes of each element have the same atomic
number, but different mass numbers.
TAKS QUESTION
Isotopes
Boron isotopes
Find the number of protons,
neutrons and electrons in each:
A)
B)
C)
D)
E)
F)
G)
H)
Carbon-14
Nitrogen-15
U-235
Hydrogen-3
Carbon-13
Helium-3
B-11
Cu-64
Periodic Table Families
List the Element Family:
Element Family
Br
K
Sr
Ce
Ar
Element Family
Fe
U
Si
C
Cs
• Orbital- the 3-d space around the nucleus
of an atom where an electron is found
most of the time. Each orbital can hold up
to 2 electrons of opposite spin.
Orbitals have different shapes:
Orbital
s
shape
spherical
p
dumbbell
d
clover or
dumbbell/donut
f
too complex
Energy sublevels around an atom
energy
sublevels
s
p
d
f
g*
# of orbitals
1
3
5
7
9
electron
capacity
2
6
10
14
18
*orbitals exist, but not used most of the time.
Aufbau Order- Energy levels &
orbital types around the atom
Aufbau order- Electrons fill orbitals closest to
the nucleus first.
• 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d,
5p,6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
Orbital notation
Electron configuration
Valence Electrons/Lewis Dot
Notation
How to calculate average
atomic mass
Pre AP Chemistry: Nuclear Equations
• Nuclear Reactions(transmutation reactions)
are represented with Nuclear Equations.
• Transmutation reactions – a reaction where one
nucleus changes element.
(# of protons)
Nuclear equations
• See board
Half-life: the amount of time it takes
for ½ of a sample to react or decay.
• The half life of Ti-48 is 47 hrs. How much
of a 250 gram sample remains after 94
hrs?
• A 100gram sample of Cd-114 decays until
only 12.5 grams remain in a total of
41years. What is the half-life for this
isotope?
TAKS QUESTION
Electron orbitals
• Orbital – a 3-dimensional space around
the nucleus which can hold up to 2
electrons, with opposite spin.
*electrons are found in their orbitals 99.9%
of the time.
Orbitals have different shapes: s, p, d, f
Orbitals have different shapes:
Orbital
s
shape
spherical
p
dumbbell
d
clover or
dumbbell/donut
f
too complex
s-orbitals: spheres
p-orbitals: dumbbell
d-orbitals: clover
(double dumbbell) or
dumbbell/donut
f-orbitals: complex
Energy sublevels around an atom
energy
sublevels
s
p
d
f
g*
# of orbitals
1
3
5
7
9
electron
capacity
2
6
10
14
18
*orbitals exist, but not used most of the time.
Orbital Notation
• Aufbau Order:
• (Nucleus)1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s,
4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f
**This is the order in which electrons fill!!!!!
You must learn the order!! Don’t worry there
is always an easier way to memorize
these things. For the Aufbau Order there
are 2 ways: With arrows or with the
periodic table! Smartboard activate!
Electron Configurations
and the Periodic Table
Figure 8.7
Orbital Notation
• Write the orbital notation for each atom:
Nitrogen, N(7 electrons)
Sodium, Na(11 e-)
Iron, Fe(__ e-)
Antimony, Sb(__ e-)
Gold, Au(__ e-)