Transcript The Nucleus - Warren County Schools

The Nucleus
Chapter 14
Section 2
What is an Atom?
• Most basic units of matter
• Everything in world made up of atoms
– Air you breathe
– Desk you are sitting in
– Your body
• Smallest particle of an element with all the
properties of the element that can combine with
other atoms to form a molecule
ATOM SIZE
• 1 PENNY = 2X1022 Cu & Zn ATOMS
(20,000,000,000,000,000,000,000)
• Thickness of aluminum foil is about
50,000 aluminum atoms stacked
How many different types of Atoms
are there?
• 92 naturally occurring elements(different types
of atoms
• 25 synthetic elements (made by scientists in
laboratory)
What is an Element?
• Matter made of atoms of only one kind
– Example: piece of aluminum foil
• Element Aluminum—many of same kind of
atom
• Each atom has same properties: shiny,
metal, flexible
NUCLEUS
•Most of the mass of an
atom is found in the
nucleus
•1 amu = 1.7 X 10
-24
g
PROTONS (+)
•Found In Nucleus
•Positive charge
•Mass = 1 amu (atomic
mass unit-SI unit for
measuring mass of atomic
particles)
NEUTRONS (o)
•Found In Nucleus
•Neutral=no charge
•Mass = 1 amu
(atomic mass unit)
ELECTRONS(-)
• Found In Electron Cloud Outside The
Nucleus
• In a neutral Atom:
# of protons= # of electrons
The atom has no charge
• Mass = almost ZERO
ELECTRONS(-)
• Comparing the masses
1,800 electrons = 1 proton
Parts of the Atom
Particle
Charge
Location
Weight
Proton
Positive (+)
Nucleus
1 amu
Neutron
Neutral
(no charge)
Nucleus
1 amu
Electron
Negative (-)
Electron
cloud
0.018 amu
Almost zero
amu = atomic mass unit
Two-Dimension Model
• Protons & neutrons placed
together in center—
nucleus
• Electrons orbit nucleus in
space called electron cloud
• Electron cloud organized
into energy levels
– 1st level—can hold 2 e– 2nd level—can hold 8 e– 3rd level—can hold 18 e-
Identifying Numbers
• How does the nucleus in an atom of one
element differ from the nucleus of an atom of
another element?
• Atoms of different elements contain different
numbers of protons
Identifying Numbers
• Atomic Number —number of protons in the
nucleus of an atom
– Hydrogen, smallest atom, has 1 proton
– Uranium, heaviest natural atom, has 92 protons
• atoms are identified by the number of protons
– The number never changes without changing identity of
element
Identifying Numbers
• Isotopes –atoms of the same element that have
different numbers of neutrons
– element carbon has 6 protons (atomic number)
– Isotopes of carbon can have 6, 7, or 8 neutrons
• Mass number—number of neutrons plus the
number of protons
Isotopes
Naming Isotopes
1. WRITE THE NAME OF THE
ELEMENT
2. FOLLOWED BY A HYPHEN
3. AND THE MASS NUMBER OF THE
ISOTOPE
CARBON-12
Isotopes of Carbon
Carbon-12
Carbon-13
Carbon-14
Mass Number
12
13
14
# protons
6
6
6
# neutrons
6
7
8
# electrons
6
6
6
Atomic Number
6
6
6
• Average atomic mass—average mass of the
mixture of an element’s isotopes
Isotopes of Hydrogen
Example:
http://education.jlab.org/glossary/isotope.html
Isotopes of Hydrogen
Reading a Periodic Table
Synthetic Elements
• Elements that are made in labs by
smashing atomic particles into a target
element
• Elements with atomic numbers 93 to
112, and 114 are synthetic elements
Radioactive Decay
• The release of nuclear particles and energy.
• When those nuclear particles released are
protons the atomic number changes and
that element changes into another
element-Transmutation
Alpha Particles
• Two protons and two neutrons
• Alpha particles are ejected during
transmutation
– Ex. Americium-241 becomes Neptunium
– All atomic particles still exist just in different
combinations
Beta Particles
• High-energy electron that comes from the nucleus
• Electron in nucleus(aka Beta Particle) comes from a
neutron that has changed to a proton and an electron
• Electron(Beta Particle) is released but proton stays in
the nucleus
– This increases the # of protons in the nucleus and changes
the element
– http://www.youtube.com/watch?v=HGE1JstspM4&feature=rel
ated
Radioactive Decay
• Is random-can’t tell which atoms will
decay, but can predict how long it will
take for half of the radioactive isotope
to decay-
HALF-LIFE
• The amount of time it takes for half of a
sample of the element to decay.
• Can range in length from fractions of a
second to billions of years.
• http://www.khanacademy.org/video/halflife?playlist=Chemistry
• http://www.youtube.com/watch?v=kHK3rF7R7M&NR=1
Carbon Dating
• Used to determine the age of dead animals,
plants(once living things-how long ago they
lived)
• Half-life for Carbon-14 is 5730 years
•
•
•
•
Carbon-12 makes up 99%
Carbon-13 makes up 1%
Carbon-14 makes up 1 part per million
Carbon-14 is radioactive and it is this radioactivity which is used
to measure age.
• knowing how many carbon-14 atoms something had before it
died can only be guessed at. The assumption is that the
proportion of carbon-14 in any living organism is constant.
Uranium-238
•
•
•
•
Used to determine the age of rocks
U-238 decays into lead 206
Half-life is 4.5 billion years
Problems- may have already been lead in rock
and some isotopes may have migrated out of the
rock-giving inaccurate dating
Uses of Radioactive Isotopes
• Medical Uses: Tracer elements or radioisotopes-used
to help diagnose disease
• Environmental Uses:
– Tracer elements watches how a plant uses a certain
element(phosphorus)
– In Pesticides/Fertilizers to follow the pesticide to see how it
moves through an ecosystem
– Water resources
– http://www.youtube.com/watch?v=K5Ks2X5TphI
• http://www.authorstream.com/Presentation/Susa
nn-48726-radioactivity-1-Slide-2-PLUMPUDDING-MODEL-ATOM-4-5-6-7-8-9-10-1112-13-14-Education-ppt-powerpoint/
QUIZ Chapter 4, Section 2
1. Particle found in the nucleus that has no
charge
2. Contains most of the mass of an atom
3. Negatively charged particle found
outside the nucleus
4. Particle found in the nucleus that is
positively charged
QUIZ Chapter 4, Section 2
5. The simplest atom is the __________
atom.
6. Particle with an unequal number of
protons and electrons
7. SI unit used for the masses of atomic
particles.
8. Draw and label a model of an atom.
Include the three particle and their
charges.
QUIZ Chapter 4, Section 2
9. Calculate the number of protons,
neutrons and electrons in carbon-14.