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Warm Up:
Dimensional Analysis Practice
The relative mass of an electron is
0.000586 amu.
a. Write in scientific notation
b. If a proton has a relative mass of 1.007276 amu, how
many electrons could fit on a proton?
c. The actual mass of an electron is 9.109 x 10-31kg.
Convert to mg
Chapter 3:
Atoms, the Building
Blocks of Matter
Atomic Theory has Evolved!
Why has the atomic theory changed through the years?
Qualitative vs. Quantitative data
Law of Conservation of Mass
Mass is neither created nor destroyed during an ordinary chemical
reaction or physical change.
Candle Lab:
C25H52 + O2 + E
CO2 + H2O + C + E
Draw a picture and explain why it
happens?
1.
2.
3.
Tear up a piece of paper. Rub the balloon against your clean,
dry (product free) hair. Hold the balloon next to the paper.
Make observations.
Rub the balloon against your hair. Hold the balloon close to
running water. Make observations.
Explain to the best of your abilities what is happening.
Pioneers of the
Atomic Theory
Chapter 3
Observant people have been looking at matter and
pondering why different phenomenon occur for
hundreds of years.
Early Philosophers
Didn’t agree!!
Dead Dude #1- Democritus
Ancient philosopher- 460BC
Matter is made of indivisible
particles.
Atomos means “that which
cannot be further broken
down”
Shortcomings
It is a conceptual definition, not based on
science.
Doesn’t talk about subatomic particles.
Dead Dude#2- Dalton
Explained the Laws
John Dalton (early 1800s)
Atom is a solid, indestructible
mass (like a billiard ball)
All Atomic Theory builds on Dalton’s Law
1. All matter is made of tiny particles
called atoms.
2. All atoms of a given element are
identical in size, mass and properties
Atoms of each element are different.
3. Atoms cannot be subdivided, created or
destroyed.
4. Compounds consist of atoms of
different elements combined together.
Compounds have constant composition
(fixed ratio of atoms).
5 Chemical reactions involve the
rearrangement of those atoms.
Through observation and experimentation we have found that
some are true, others are not!
1. All matter is made of tiny particles called
atoms.
2. All atoms of a given element are identical
in size, mass and properties
3. Atoms of each element are different.
4. Atoms cannot be subdivided, created of
destroyed.
5. Compounds consist of atoms of different
elements combined together. Compounds
have constant composition (fixed ratio of
atoms).
6. Chemical reactions involve the
rearrangement of those atoms.
Dead Dude #3
J.J Thomson- 1850
A ball of positive mass
containing a number of
electrons that are
embedded.
Getting the idea that there
are protons and electrons
(nucleus).
Shortcomings
Doesn’t explain the existence of electrons outside the nucleus
or their importance in bonding.
No neutrons- can’t explain radioactivity or the existence of
isotopes.
What did experiments with the
cathode ray tubes teach us?
http://www.youtube.com/watch?v=O9Goyscbazk&safety_mode
=true&persist_safety_mode=1&safe=active
Late 1800’s
Discovery of and
experiments using
the cathode ray tube
led to our
understanding of the
electron.
Millikan Oil Drop Experiment
Millikan Oil Drop Experiment
We learned what the actual charge of an electron is– pretty
cool!
Henri Becquerel- 1897
Researched newly discovered
X-rays (Phosphorescence).
Accidently discovered that
uranium emits radiation that
could be measured using
photographic plates.
Discovered Radioactivityelectrically charged particles.
The Dr’s Curie- 1898
Discovered new elements- Polonium
and Radium.
Very unstable elements that give off
energy.
This led to an under- standing of
Alpha, Beta and Gamma particles.
 Rutherford Model- 1905
Dead Dude #4
Mass of the atom is
concentrated in the center
of a positively charged
region called the nucleus.
The Planetary Model
Gold Foil Experiment- Draw this and
write about the experiment.
Ask Ben…
Gold Foil Experiment
Shortcomings
Doesn’t place the electrons.
Doesn’t include neutrons.
Warm Up- Leave enough space to
finish the atomic theory ppt
(2 more slides)
The actual mass of a proton is
1.673 X 10-27 kg.
a. What is the mass of 6300 protons?
b. Convert your answer to decigrams.
c. Convert your answer to megagrams.
Bohr Model-1920
Believed that electrons traveled
in precise orbits around the
nucleus of an atom
Schrodinger Quantum Mechanical
The nucleus is at the center of
Model.
the atom and the electrons are
Describes mathematically the
wave properties of electrons
and other very small particles
in the electron cloud.
Reading the Periodic Table Cell
Practice
Element
Symbol
Protons
Neutrons
Magnesium
23
Ca
8
Chlorine
8
Electrons
How did you do?
Element
Symbol
Protons
Neutrons
Electrons
Magnesium
Mg
12
24-12 =12
12
Vanadium
V
23
51-23 = 28
23
Calcium
Ca
20
41-20 = 21
20
Oxygen
O
8
8
8
Chlorine
Cl
17
35-17 = 18
17
Build an Atom Activity…
Get a computer… type in
Build an atom phet
Write everything in bold print
Answer every question…
You have about 35 minutes to get this done!
Draw the Bohr Model for the following
atoms….
Na
N
Cl
The octet rule says that atoms will be more stable when
they have a full outer shell… usually 8 valence electrons.
Ions
Ions are atoms that gain or lose electrons to obtain a full outer
shell (a complete octet).
Cations- lose electrons
Anions - gain electrons
Ions
The number of protons does not change in an ion
The number of neutrons does not change in an ion.
So, both the atomic number and the atomic mass remain the
same.
How do I calculate the average
atomic mass of an element?
Look at just about any element on the periodic table. Do you
notice that most of the atomic masses listed are not whole
numbers.
Hmmmmm……..
Can we have a part of a
proton or neutron?
I don’t think so!
What we are looking at is the average
atomic mass of the isotopes.
Some Kr atoms are 83amu
others are 84amu
So… how do they get that number?
The calculation:
1. Write the percent abundance (given)
2. Change to relative abundance
3. Multiply relative abundance by mass
4. Add’em up!
Easy as pie!
Let’s talk donuts!
Veggium Lab
Let’s Practice!Please copy the table into CB
Element
Oxygen
Calcium
Aluminum
Tungsten
Nickel
#Protons
#Neutrons
#Electrons
Let’s Practice!- Output p.23
Please copy the table into CB
Element
#Protons
#Neutrons
#Electrons
Oxygen
8
16 – 8 = 8
8
Calcium
20
20
20
Aluminum
13
27-13=14
13
Tungsten
74
184-74=110
74
Nickel
28
59-28=31
28