Atomic Structure powerpoint

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Transcript Atomic Structure powerpoint

Elements are made of atoms = the
smallest particle that has all the
characteristics of the element
How Small is an Atom?
• A copper penny contains 2.4 x 1022 atoms
• Earth’s population is approx. 7 x 109
• A scanning tunneling microscope makes it
possible to see individual atoms
• TED
Scanning Tunneling Microscope
Atom Image
Subatomic Particles
• Mass of atom is generally protons + neutrons,
majority of mass is in nucleus
• Mass of proton = 1
• Mass of neutron = 1
• Mass of electron = 1/2000
• (mass of H proton = 1 = is standard)
Subatomic Particles
Subatomic
Particle
Proton
Neutron
Electron
Charge
Location
Why?
Distinguishing Between Atoms
Atomic Number (Z)
• Found on the periodic table
• Is equal to the number of protons
• Each element has its own atomic #
• # protons = # electrons
Average Atomic Mass
• Also found on the periodic table
• Is the average mass of all of the atoms of that
element
• Mass number = (A) actual mass of one atom
• Mass number = protons + neutrons
Carbon-12?
When written in this format…
12 is the mass #
Practice with a Partner
Atom
Symbol
Atomic
#
Aver
Atomic
Mass
Mass #
Lithium
7
Boron
9
Carbon
12
Nitrogen
14
Oxygen
16
Helium
4
Sodium
23
#
protons
#
neutrons
#
electrons
Isotopes
• Atoms of the same element that have different
masses
• Have different masses because they have
different numbers of neutrons
• # protons always the same
Example
• Carbon isotopes
▫ Carbon-12
▫ Carbon-13
▫ Carbon-14
• Might also be written C-12, C-13, C-14
• Or
Nuclear Formulas
• Used to write isotopes…
Isotopes
• How are isotopes similar?
• How do they differ?
• Isotopes are chemically alike b/c they have
identical numbers of protons & electrons
Average Atomic Mass
• How is it calculated?
• Based on the relative abundance of the naturally
occurring isotopes of the element
• Each isotope has a fixed mass and a natural %
abundance
Question
• With the following information, calculate the
average atomic mass of chlorine:
▫ 76% of chlorine isotopes found naturally have a
mass of 35
▫ 24% of chlorine isotopes found naturally have a
mass of 37
Warm Up
1/15/2014
• P. 85 2-3
• P. 87 6-9
• Calculate average atomic mass given the
following information:
▫ Carbon-12 is found naturally 98.89% of the time
▫ Carbon-13 is found naturally 1.11% of the time
Warm Up
1/16/2014
• Write the procedure for determining average
atomic mass (paragraph format, complete
sentences).
• Quiz tomorrow—cumulative
• Homework tonight
Atomic Theories
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Democritus
John Dalton
JJ Thomson
Ernest Rutherford
Niels Bohr
Schrodinger
“Atom” & Democritus
• 400 BC
• Called nature’s basic particle an atom
• Atom (Greek) means uncuttable or indivisible
• No experimental evidence
Dalton’s Atomic Theory (1808)
▫ All matter is composed of tiny indivisible particles
called atoms
▫ Atoms of the same element are identical
▫ Atoms of different elements can physically mix
together or can chemically combine with one another
in simple whole number ratios to form compounds
▫ Chemical reactions occur when atoms (in compounds)
are separated, joined, or rearranged
Dalton’s Atomic Theory
• Much of Dalton’s theory is accepted …except ?
• Except that atoms are indivisible AND that all
atoms of an element are identical
Thomson & Plum Pudding Model
• 1897
• Discovered the electron
• His model proposed that negatively charged
particles were randomly distributed within a
pudding of positively charged particles
Rutherford & The Gold Foil
• 1909
• Discovered the atom’s nucleus
• He bombarded a thin, gold foil with fast moving
alpha particles (p 72-73)
Rutherford & The Gold Foil
• A small amount of particles were deflected by the tiny
nucleus; most of the particles passed on through
• He concluded the volume of the atom was mostly empty
space
Bohr’s Atomic Model
• 1915
• Electrons organized in
energy levels or shells
around a nucleus of
protons and neutrons
• A “planetary” model—not
entirely correct
The Electron Cloud & Schrodinger
• Is a probability model
• Describes a cloud like
region where the electron
is likely to be
• Based on mathematical
equation
Project Time
A Closer Look…the Bohr Model
Video
Bohr’s Model of the Atom
• Scientists found that when an electric current is passed
through a glass tube that contains hydrogen gas, the tube
emits light
• When this light is passed through a prism, four narrow
bands of bright light are observed against a black
background
• This is hydrogen’s line emission spectrum
• Bands are at specific wavelengths, which are unique to
each element
Niels Bohr
• Niels Bohr proposed a model for the hydrogen
atom that explained the spectrum of the
hydrogen atom.
• The Bohr model was based on the following
assumptions:
Bohr’s Model of the Hydrogen Atom
▫ Electrons are arranged in concentric circular paths or
orbits around the nucleus
▫ Electrons in a particular path have a fixed energy
▫ The energy of the electron in an orbit is proportional to
its distance from the nucleus. The further the electron
is from the nucleus, the more energy it has.
▫ An electron can either gain or lose energy inside this
orbit, electrons can move up or down to another orbit
Continued…
• A quantum of energy = is the amount of energy
required to move an electron from its present energy
level to the next higher one
• Light is absorbed when an electron jumps to a higher
energy orbit and emitted when an electron falls into a
lower energy orbit
Continued…
• The energy of the light emitted or absorbed is exactly
equal to the difference between the energies of the orbits
• The energy given off is electromagnetic radiation
• Is given off as photons (particle of light with no mass)
Continued…
• Lowest energy state of atom = ground state
• Higher energy state of atom = excited state
• Neon signs—excited neon atoms emit light
when falling back to the ground state
Project Time
Reminder…Quiz tomorrow
Warm Up
1/17/2014
• How did Bohr’s model of the atom differ from
Schrodinger’s?
Modern Atomic Theory
Electron Cloud Model
• AKA quantum mechanical model
• Clouds of probability = where electrons are
most likely to be
• Electrons are located in orbitals (not orbits)
Electron Cloud Model
• 4 types of orbitals: s, p, d, f
• Each orbital can only hold 2 electrons
Warm Up
1/21/2014
• Construct a table to compare subatomic
particles.
Warm Up
1/24/2014
• Create a Venn diagram to compare the Bohr
model to the electron cloud model.
• Homework DUE
• Quiz today
Warm Up
1/27/2014
• Given an isotope for fluorine, fluorine-19…
• What is Z?
• What is A?
Quizzes
• Dropped one question
• 2nd block 84
• 3rd block 86
What are ions?
Why would ions form?
Atoms with a charge
When they gain, lose, or share
electrons
But…why would they do this?
What is the Octet Rule?
Says that atoms tend to gain, lose
or share electrons so as to have
eight electrons in their outer
electron shell…
More specifically, the number of
electrons needed to fill the s and p
sublevels of that energy level
Practice
Nuclear Chemistry
How Atoms Combine
Section 3.2
Chemical Properties
• Chemical properties = how reactive an atom is
• Does it like to combine with other atoms or is it
stable alone?
• Which groups on the periodic table are reactive?
• Which groups are stable?
Compounds
• A substance that is composed of atoms of 2 or
more different elements that are chemically
combined
• Example = NaCl
• Why do these two atoms like to combine?
(draw)
Types of Bonds
• Ionic bonds—when atoms lose or gain electrons
• Example = _____________
• Covalent bonds—when atoms share electrons
• Example = ______________
(draw)
Compounds
• Atoms want their outer energy level filled with
electrons, in most cases this is 8 electrons
• Which groups on the periodic table would you
predict would commonly form bonds together?
• Class Bonding Activity
Warm Up
8/30/12
Complete Section
Assessment 3.1
#1-5 on page 59
Group Assignment
• Chemical Reactivity worksheet
Independent Notebook Assignment
• Vocabulary section 3.2 (page 60)
Independent Assignment
• Create a poster—to display a large drawing of an
atom…the element will be assigned to you.
• Format: see example
• Grading: based on neatness & accuracy.
Element Assignment
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H
He
Li
Be
B
C
N
O
F
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Ne
Na
Mg
Al
Si
P
S
Cl
Ar
Warm Up
8/31/12
What group # is chlorine in?
What is its symbol?
List everything that you can learn
about chlorine based its location in
the periodic table. Include what
other elements it might bond with.
Agenda
• Quiz
• Project Presentations