Introduction to Atoms. Vocabulary Atom- Sub-atomic Particles- Nucleus- Atomic Models-
CH 4 : THE ATOM - Chemistry · 2019. 10. 24. · NUCLEUS OF AN ATOM •Nucleus- VERY small region...
Transcript of CH 4 : THE ATOM - Chemistry · 2019. 10. 24. · NUCLEUS OF AN ATOM •Nucleus- VERY small region...
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CH 4 : THE ATOM
On the first right side page (after Ch 3 notes):
• Create a Cover page for Chapter 4.
• Make atom design the whole page and label the
parts of the atom.
• Include COLOR!
• I have a sample one online you can use
On the back side of cover page (left side),
• Paste in the “I can” Learning Objectives #10-22.
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TN Ch 4.1 Date
Title and
Highlight
Topic:
EQ:
NOTES:
Write out the notes from my website.
Use different types of note-taking
methods to help you recall info (different
color pens/highlighters, bullets, etc)
When I lecture we will add more info, so
leave spaces in your notes
Summary Questions:
2-3 sentences… What did you learn
today from the notes?
THESE ARE AT THE VERY END OF
NOTES
Right Side – NOTES ONLY
Reflect
Question:
Reflect on
the
material by
asking a
question
(its not
suppose to
be
answered
from
notes)
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TN Ch 4.1
Title and
Highlight
DRAW ANY PICTURES, FIGURES,
AND WRITE OUT ANY PRACTICE
PROBLEMS/QUESTIONS.
WE WILL ANSWER THEM TOGETHER.
LEAVE SPACES SO WE CAN ANSWER
QUES.
LEFT Side – PICTURES, PRACTICE PROBLEMS, ETC
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TOPIC: ATOMIC THEORY
EQ: Explain the history & the discovery of the atom
Ch 4.1-4.2
READ Ch 4.1-4.2 (pg. 93-95) first then write notes
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CH 4.1 ATOMS • Atoms are incredibly small.
• To get an idea of how small atoms are: • if every atom within a small pebble were the size
of the pebble itself, the pebble would be larger than Mount Everest.
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ATOMS AND ELEMENTS• ATOM - “Building Blocks of Matter”• An atom is the smallest particle of an element that retains the chemical properties of that element.
• An element is a substance that cannot be broken down into simpler substances.
• There are about 91 different elements in nature, and consequently about 91 different kinds of atoms. (The other 27 are synthetic – man made elements)
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CH 4.2
The Atom: From Philosophical Idea to Scientific Theory
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THE EARLY ATOM
• As early as 400 B.C., Democritus called nature’s basic particle the “atomon” based on the Greek word meaning “indivisible”.
• His theory: Matter could not be divided into smaller pieces forever, eventually the smallest possible piece would be obtained.
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ATOMS
▪To Democritus, atoms were small, hard particles that were all made of the same material but were different shapes and sizes.
▪Atoms were infinite in number, always moving and capable of bonding together.
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THE EARLY ATOM
• Most influential philosopher, Aristotle rejected Democritus’ atom theory b/c different from his ideas
• Criticized Democritus’ idea that atoms moved through empty space
• Aristotle succeeded Democritus and did not believe in atoms. Instead, he thought that all matter was continuous. It was his theory that was accepted for the next 2000 years.
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WHY?
• In the end….. Aristotle was wrong in the end.
Aristotle favored
the earth, fire, air
and water
approach to the
nature of matter.
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DALTON’S ATOMIC THEORY• John Dalton (1766-1844)
• English Chemist and schoolteacher
• In 1808,performed a number of experiments that led to the idea of atoms…..over 2000 years later after Democritus/Aristotle theory.
I was a
school
teacher at
the age of
12!
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DALTON’S ATOMIC THEORY
1. All matter is composed of extremely small particles called atoms.
2. Atoms of a given element are identical in size, mass, and other properties.**
3. Atoms cannot be subdivided, created, or destroyed.**
4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
5. In chemical reactions, atoms are combined, separated, or rearranged.
**Today, we know these parts to be wrong!!
http://tm.ask.com/r?t=c&s=p&sv=0a30052b&uid=0BC1ACC9982C64134&sid=3444474eb444474eb&o=0&id=30751&p=/fr&u=http://www.juliantrubin.com/imagesc/dalton1.gif
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• Was Dalton’s theory a huge step toward our current model of matter?
• Yes!!! It was a breakthrough in our understanding of matter.
• Was all of Dalton’s theory accurate?
• No!!!
Dalton’s Atomic Theory
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FLAWS OF DALTON’S THEORY…
#2. Atoms of a given element are identical in size, mass, and other properties.
#3. Atoms cannot be subdivided, created, or destroyed.
Isotopes – atoms with the same
number of protons but a different
number of neutrons
Subatomic particles – electrons,
protons, neutrons, and more
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SUMMARY:
Let’s reflect….
What did you learn today from the notes?
(2-3 sentences)
RIGHT side - THESE ARE AT THE VERY END OF NOTES
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TOPIC: SUBATOMIC PARTICLES
EQ: Explain the history & the discovery of the 3 subatomic particles in an atom
Ch 4.3
READ Ch 4.3 (pg. 95-97) first then write notes
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CH 4.3 - DISCOVERY OF THE SUBATOMIC PARTICLES
• The discovery of the subatomic particles came about from the study of electricity & matter.
• Benjamin Franklin’s kite experiment in 1752 demonstrated that lightning was electrical.
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DISCOVERY OF THE ELECTRON
• 1870’s - many experiments were performed in which electric current was passed through gases at low pressures
• These experiments were carried out in glass tubes called cathode-ray tubes.
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Electric CurrentElectric Current
Draw this with
notes in color!!!
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DISCOVERY OF THE ELECTRON
• The rays traveled from cathode (negative) to anode (positive).
• Negatively charged objects deflected the rays away.
• Therefore, it was determined that the particles making up the cathode rays were negatively charged.
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THOMSON’S PLUM PUDDING MODEL
• In 1897, the English scientist J.J. Thomson provided the first hint that an atom is made of even smaller particles.
(1908 Nobel Prize in Chemistry)
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THOMSON’S PLUM PUDDING ATOMIC MODEL
Thomson believed that the electrons were like plums
embedded in a positively charged “pudding,” thus it
was called the “plum pudding” model.
Draw this with
notes in color!!!
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• So….. J. J. Thomson discovered the electron.
• found that e- are negatively charged.
• e- are much smaller and lighter than atoms.
• every element (atom) has e-.
• He proposed that atoms must contain + charge that balanced the - charge of electrons.
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Millikan’s Oil Drop
Experiment
Robert Millikan (1909): Millikan’s Oil-drop ExperimentDiscovered the mass and charge on the electronCharge of electron: -1
Mass of electron = 9.1 x 10-28 g
004_MILLIKANOIL.MOV004_MILLIKANOIL.MOVfile:///C:/1213 School Year/Honors Chemistry/Chapter 2 Atoms Molecules Ions/flash shockwave animations/02_Millikan_Oil_Drop.swf
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RUTHERFORD’S GOLD FOIL EXPERIMENT• 1911 - English
physicist Ernest Rutherford
• Rutherford’s experiment involved firing a stream of tiny positively charged alphaparticles at a thin sheet of gold foil(2000 atoms thick)
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RUTHERFORD’S FINDINGS• Most of the positively
charged particles passed through the gold foil without changing course.
• Some of the positively charged particles did bounce away from the gold sheet as if they had hit something solid.
Draw this with
notes in color!!!
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(1) Most of the atom is more or less ______ _______.
(2) The nucleus is very _________ and ___________.
(3) The nucleus is ______________ charged due to protons.
(4) The nucleus (protons and neutrons) is 99.97% of an atom’s mass.
(5) The electron cloud = majority of volume
• SO……. atoms is neutral: the positive (nucleus) balances out the negative electrons
• So, why do electrons stay surrounded around the nucleus?
“Opposites attract”
empty space
densetiny
positively
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A SUMMARY OF THE NATURE OF ELECTRICAL CHARGE•Positive and negative
electrical charges attracteach other.
•Positive–positive and negative–negative charges repel each other.
•Positive and negative charges cancel each other so that a proton and an electron, when paired, are charge-neutral.
Draw this with
notes in color!!!
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Rutherford’s Model of
the Atom
2.2
Draw this with
notes!!!
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James Chadwick (1932)
Discovered the neutron.
The neutron has about the same mass as
the proton.
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• After the proton & electron was discovered….
• The Neutron was discovered last (almost 30 years later) out of all the subatomic particles, why?
• Scientist knew the charge of nucleus (+) and knew the mass of nucleus (came from proton). But their calculations were off by half…. could not figure out why the nucleus was so heavy if the proton only had a certain mass.
• There must be a third subatomic particle that weighed as much as a proton, but with no charge!
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Democristus
400BC
Aristotle
4 elements
Dalton (1803)
Atomic Theory
Thomson (1897)
Plum Pudding Model
Cathode Ray Tube
electrons
Rutherford (1911)
Gold Foil Experiment
Proton & Nucleus (Mass and Volume)
Millikan (1909)
Charge & Mass
of electron
Chadwick (1932)
Neutron
THE ATOM - TIMELINE Draw this left side!!!
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SUMMARY:
Let’s reflect….
What did you learn today from the notes?
(2-3 sentences)
RIGHT side - THESE ARE AT THE VERY END OF NOTES
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TOPIC: THE STRUCTURE OF THE ATOM
EQ: What is the difference between protons, neutrons, and electrons?
Ch 4.4
READ Ch 4.4 (pg. 97-99) first then write notes
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THE ATOM
• Atom - the smallest particle of an element.
• How small is an atom?
• Copper atoms in penny –29,000,000,000,000,000,000,000 (2.9 x 1022)
Copper
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THE STRUCTURE OF THE ATOM
• The atom is composed of two main regions: the nucleus & the electron cloud.
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THE ATOM
• The atom is made up of three subatomic particles.
Draw this with
notes in
color!!!
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NUCLEUS OF AN ATOM
• Nucleus- VERY small region located at the center of the atom. The nucleus accounts for most of an atoms mass but very little volume, making it a very dense region.
• The nucleus contains protons & neutrons.
proton = p+ neutron = no
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ELECTRON CLOUD OF AN ATOM
• The electron cloud is the negatively charged region of the atom that accounts for most of the atom’s volume but very little of the atom’s mass.
electron = e-
The electron cloud is
composed of electrons.
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SUBATOMIC PARTICLESParticle Symbol Location Electrical
charge
Mass
(amu)
Actual
Mass (g)
Electron e- Outside
nucleus
-1 1/1840 9.11x10-28
(About 2000
times smaller
than Proton
and neutron)
Proton p+ Nucleus +1 1
1.67x10-24
Neutron n0 nucleus 0 1
1.67x10-24
They have the SAME Mass
Draw this left
side!!!
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PRACTICE PROBLEMS #1
❑ What are the two main regions of the atom?
❑What is the charge on the nucleus?
left side!!!
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SUMMARY:
Let’s reflect….
What did you learn today from the notes?
(2-3 sentences)
RIGHT side - THESE ARE AT THE VERY END OF NOTES
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TOPIC: ELEMENT NAMES, SYMBOLS, & THE STRUCTURE OF THE ATOM
EQ: How do you write an element’s symbol? How many p+, no, & e- does
any element have?
Ch 4.5
READ Ch 4.5 (pg. 99-101) first then write notes
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CH 4.5: CHEMICAL SYMBOLS• Chemists use chemical symbols to represent elements.
• The chemical symbol consists of 1 or 2 letters.
• The first letter ALWAYS ______________.
• The next letter is _______________.
capitalized
lowercase
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CH 4.5 ELEMENTS: ORIGINS OF THE NAMES OF THE ELEMENTS
• Most chemical symbols are based on the English name of the element.
• Some symbols are based on Greek or Latin names, which include the following:
potassium K kaliumsodium Na natriumlead Pb plumbummercury Hg hydrargyrumiron Fe ferrumsilver Ag argentumtin Sn stannumcopper Cu cuprum
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JUST READ!!!!• Early scientists gave newly discovered
elements names that reflected their properties:
• Argon, from the Greek argos, means “inactive,” referring to argon’s chemical inertness.
• Other elements were named after countries:
• Polonium after Poland • Francium after France• Americium after the United States of
America.
• Other elements were named after scientists. • Curium after Marie Curie• Einstenium after Albert Einsten
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THE PERIODIC TABLE OF THE ELEMENTS LISTS ALL KNOWN ELEMENTS ACCORDING TO THEIR ATOMIC
NUMBERS.
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• The # of protons in the nucleus of an atom that identifies an element.
• The # of protons in the nucleus of an atom is its atomic number.
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SYMBOL NOTATION
XMass
number
Atomic
numberSubscript →
Superscript →
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Atomic number (Z).
Protons determines the identity of the element.
A# = p+ = e- (atoms are neutral)
The Mass Number (A),
(rounded to the nearest
integer)
Mass# = p+ + no
A is always the largernumber than Z.
# of neutrons = mass number – # p+
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LOOK FOR THE ELEMENT CHLORINE…..
LET’S WRITE HIS CHEMICAL SYMBOL
NOTATION
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Cl35
17
MASS
NUMBER
ATOMIC
NUMBER
NUMBER OF
PROTONS
# PROTONS+
# NEUTRONS
Symbol notation
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LOOK FOR THE ELEMENT CARBON…..
LET’S WRITE HIS CHEMICAL SYMBOL
NOTATION
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SYMBOL NOTATION
Element followed by a hyphen – mass#
Carbon-12
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• Difference between Mass and Atomic weight
• Atomic weight is the weight of all the isotopes for that element (decimal #)
• Mass number is the rounded number for the atomic weight.
• Example: Copper
• Atomic weight – 63.546
• Mass number - 63
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PRACTICE PROBLEMS
Element Atomic
#
Mass
#
p + n o e - Symbol
Oxygen - 8
33 42
-31 31 15
91 140
Sodium - 23
Uranium - 238
80
Br
35
26
Mass number
left side
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SUMMARY:
Let’s reflect….
What did you learn today from the notes?
(2-3 sentences)
RIGHT side - THESE ARE AT THE VERY END OF NOTES
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TOPIC: ISOTOPES
EQ: What is an isotope and how does it affect the atom?
Ch 4.8
READ Ch 4.8 (pg. 109-111) first then write notes
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4.8 ISOTOPES: WHEN THE NUMBER OF NEUTRONS
VARIES
• All atoms of an element have the same # of protons.
• They do not have the same # of neutrons.
• Atoms with the same # of protons but different # of neutrons are called isotopes.
• Example Hydrogen
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ISOTOPES
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EXAMPLE OF AN ISOTOPE
Cl35
17 Cl37
17
20 NEUTRONS
ATOMIC MASS
18 NEUTRONS
ATOMIC NUMBER
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Review…. How to write Symbol Notation
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Practice Problem #1
Circle which of the following are isotopes.
40
20 X40
18 X42
20 X40
19 X43
20 X
left side!!!
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Practice Problem #2
Determine the number of protons, neutrons and electrons in the neutral (non-charged) isotopes of the following atoms:
88
38 Sr84
38 Sr
left side!!!
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SUMMARY:
Let’s reflect….
What did you learn today from the notes?
(2-3 sentences)
RIGHT side - THESE ARE AT THE VERY END OF NOTES
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TOPIC: AVERAGE ATOMIC MASS
EQ: How do you calculate average atomic mass?
Ch 4.9
READ Ch 4.9 (pg. 111-113) first then write notes
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Average Atomic Mass
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• The atomic masses listed in the Periodic Table are a “weighted average” of all the isotopes of the element.
• Units = atomic mass unit (amu)
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In general, atomic mass is calculated according to the following equation:
Average Atomic mass =
Step 1: Convert the percent natural abundances into decimal form by dividing by 100.
Step 2: Multiply the decimal abundances with the isotopes mass.
Step 3: Add up the atomic masses for each isotope. This is the average atomic mass for that element (should be close to the number listed on P.T.)
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• All elements have their own unique percent natural abundance of isotopes.
• Naturally occurring chlorine consists of
75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu).
• Which isotope is the most abundant?
• What is the Average Atomic Mass of Cl?
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• Gallium has two naturally occurring isotopes: Ga-69, with mass 68.9256 amu and a natural abundance of 60.11%, and Ga-71, with mass 70.9247 amu and a natural abundance of 39.89%. Calculate the atomic mass of gallium.
Left side: Leave 5 lines of space to solve in class
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• Write Question #97 from textbook
Left side: Leave 5 lines of space to solve in class
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SUMMARY:
Let’s reflect….
What did you learn today from the notes?
(2-3 sentences)
RIGHT side - THESE ARE AT THE VERY END OF NOTES