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Monday October 4, 2010. (Review of Important Concepts). Bell Ringer Monday, 10-4-10. List the five major points of Dalton’s Atomic Theory. All matter is composed of extremely small particles called atoms. - PowerPoint PPT Presentation
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MondayOctober 4, 2010
(REVIEW OF IMPORTANT CONCEPTS)
Bell RingerMonday, 10-4-10
List the five major points of Dalton’s Atomic Theory. All matter is composed of extremely small particles called atoms.
Atoms of a given element are identical in size, mass and other properties: atoms of different elements differ in these ways.
Atoms cannot be subdivided, created or destroyed. Atoms of different elements combine in simple
whole-number ratios to form compounds In chemical reactions, atoms are combined,
separated or rearranged, not created nor destroyed.
Announcements
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Assignment Currently Open Page Date of Notes on Website Date Issued Date Due
WS: Atomic Structure 73-74 10/1 10/8
Review of Important Concepts
Steps in the Scientific Method
1. ask a question 2. do background research 3. construct a hypothesis 4. test your hypothesis by
doing an experiment 5. analyze your data and
draw a conclusion 6. communicate your
results
Reading a Graduated CylinderHow much liquid is in each
cylinder?
Density of LiquidsLess dense liquids float on top of
more dense liquids.Honey has the highest density of all of the liquids
in this column.
Karo syrup is less dense than honey, so it floats on
top of the honey.
The liquids progressively get less dense as you go
up the column.
Which liquid has the lowest density?
Physical vs. Chemical Properties
Physical Propertiesphase – solid,
liquid, gas, plasma
phase changes – melting point, boiling point,
freezing point, condensation
pointpolarity and non-
polarity of molecules
Chemical Properties
burningrusting
tarnishingdigesting
Particles in Phase
Particles in the solid phase
Particles in the liquid
phase
Particles in the gas phase
In a tight, rigid
structure
Occupying the bottom portion of
the container
Flying around throughout the
container
Differences in Physical Properties
Recall the saltwater solution that you had
in your mixture separation lab.
If you didn’t have a way to boil the water
off, you could have set the beaker on a table for several days and
the water would have eventually evaporated
out of the beaker, leaving the salt.
In order for this to happen, what category of matter must saltwater be?
Answer: a mixture!
Independent vs. Dependent Variables
Things that change are called “variables.”
In an experiment, there can only be two variables: the independent
variable and the dependent variable.
At the beginning of the experiment, the experimenter
changes the independent variable to kick things off.
As the experiment proceeds, another variable will change, the dependent variable, as a result of
the independent change.
Physical vs. Chemical Changes
When a physical change occurs, the material that changes does
not change its chemical identity.For example, when a log is cut in half, it’s still a log. No new substances are produced.
When a chemical change occurs, the material that changes does
change its chemical identity.For example, when a log is burned, it’s no longer a log – it’s now ash, smoke, carbon dioxide,
and water vapor. New substances are produced.
DensityA sample of material is in the
shape of a cube. The cube is 1.26 cm long, 1.43 cm wide, and 0.650 cm high. The cube has a density of 4.26 g/cm3. What is the mass
of the cube?Density = mass/volume
Therefore, mass = density x volume
mass = 4.26 g/cm3 x (1.26 cm x 1.43 cm x 0.650 cm)mass = 36.4 g
Important Safety EquipmentSome safety equipment is meant
to prevent an accident from happening.
Determine whether each of the following is preventative or is
designed to lessen an accident’s effect after it’s already happened.
Some safety equipment is meant to be used after an accident has
occurred and is designed to lessen the accident’s effect.
Aprons, goggles, first aid kit, fume hood, shower, fire extinguisher, eyewash
The Strong Nuclear ForceGenerally, particles that have the same
electromagnetic charge repel one another, therefore, we would expect a nucleus with
more than one proton to be unstable.
However, when two protons are extremely close to each other, there is actually a
strong attraction between them.
A similar attraction exists when neutrons are very close to each other, or when protons and neutrons are very close
together.
The Structure of the Atom
The Nucleus• The Strong Nuclear Force
– These short-range proton-neutron, proton-proton, and neutron-neutron forces hold the nuclear particles together and are referred to as nuclear forces.
The Structure of the Atom
Together, protons, neutrons and electrons
are referred to as subatomic particles.
The Structure of the Atom
Charge and Mass of the Sub-atomic Particles
Some substances are
made up of only
one kind of atom
- Element
s
Exactly how does one element differ from another?
It is the number of
protonsin an atom that distinguishes an
atom of one element from the
atom of another element
All atoms of the same
element will have the same number
of protons,
and atoms ofdifferent elements will have different numbers
of protons
Adding or removing aproton from
an atom usually
takes (or releases)
huge amounts of
energy
Most atoms are very
stable. Even if atoms bond or
break apart during
chemical reactions,
the number of protons in each atom
always remains the
same.The atoms themselves
are only rearranged in different
combinations
We can refer to
each element by the
number of
protons its
atoms contain
This unique number is called the
atomic numbe
r
Atomic numbers
start at 1, with the element
hydrogen, and go up by
ones toThe synthetic
element number 114. The heaviest
elements have been
created in alaboratory
and have not been seen in
nature
In addition to the atomic number, every atomic
nucleus can be described by its
Mass Number
The massnumber is equal to
the total number
of protons
plus neutrons
in the nucleus of an atom
Atoms of the same
element have the
same number of
protons
Atoms of the same element
can havedifferent numbers
of neutrons
In the Periodic Table, the atomic number increases by one whole number at a time. This is because you add one proton at a time for each element.
The atomic masses however, increase
by amounts greater than one. This difference is
due to the neutrons
in the nucleus. Neutrons add mass
to the atom, but do not change its
charge
The total number of protons and neutrons in the nucleus of an atom is
called the
mass number
Sometimes, the mass number of an element
is included in the symbol. By
convention, the mass number is written as a superscript above thesymbol and the atomic number as a subscript
below the symbol
You can find the number of
neutrons by subtracting the atomic number from the mass number. How
many neutrons does the carbon
atom above have?
isotope notation
Many elements have atoms with different numbers of neutrons.
These different forms of the same element are
called
IsotopesAny given Isotope of an
element is called a nuclide.
Isotopes are atoms of the same element that have different numbers
of neutrons
The three Isotopes of Hydrogen
Mass # 1+0=1 Mass # 1+1=2Mass # 1+2=3
Atomic Mass Units are used to assign masses
to an atom.One AMU is
exactly 1/12 the mass of a carbon-
12 atom.Average atomic mass is the weighted average of the atomic masses of the naturally occurring
isotopes of an element.Cu: 69.17% Cu-63with an atomic mass of
62.929 598 amu, and 30.83% Cu-65, with an atomic mass of 64.927 793.
0.6917 x 62.929 599 amu + 0.3083 x 64.927 793 amu = 63.55 amu.
ExampleHow many neutrons are present in an atom of carbon that has a mass number of 14?
SolutionThe mass number is the number of protons plus the number of neutrons.
(1) You are asked for the number of neutrons.
(2) You are given that it is carbon-14. Carbon has 6 protons.
(3) The relationship is n + p = mass number
(4) Solve for nn= mass number -p
(5) Plug in numbers and get answern = 14 - 6 = 8
There are 8 neutrons in a carbon-14 nucleus.
Why aren’t there infinite numbers of elements, each with an atomic number
greater than the one before it?The answer may lie in the forces that keep a
nucleus together.
Remember that positive charges
repel each other. In the
nucleus,however,
positive protons and neutral neutrons sit side by side.
Because theprotons are
repelling each other, they (and
the nucleus) should fly apart!
The nucleus stays together because there is another force acting that is stronger than the
repulsion of the protons for each other.
Because it is stronger than theelectromagnetic force, scientists
call it the Strong Nuclear Force.
Unlike gravity,which can reach millions of miles, the strong force only
acts on very shortdistances. The effective
distance for the strong force is so short, we do not feel itoutside the nucleus of an
atom.
Atoms are electrically neutral.
Electrons are never all in one place at the same time.
Instead, they literally buzz around the nucleus at a very
fast rate, or frequency. Because of this behavior, we can refer to the entire space that electrons occupy as the
electron cloud
An atom of helium has an atomic
number of 2 andtwo protons in its nucleus. A neutral
atom of helium would therefore have two
electrons, which stay close to the nucleus because the positive
protons and thenegative electrons attract each other.
An atom of silver has an atomic number of47 and 47 protons in its nucleus. A neutral atom of silver would
therefore have 47 electrons.
Are these electrons randomly
placed or are they
organized in some way?
The current model of the atom describes the area of the electron cloud that each electron occupies
as an Energy State.
The farther away from the nucleus the electron is found, the
higher its energy state.
Therefore, the electron
cloud isdivided into
energy levels. The first energy
level is closest to
the nucleus and has the
lowest energy.
Electrons that occupy this
level are at a lower energy
state than electrons that
occupy the second
energy level, which is
farther from the nucleus.Each energy
level can hold up to a specific
number of electrons
Like the layers of an onion, as the energy levels
extend farther from the nucleus, they get larger in
diameter and can hold more electrons. The
maximum number each level can hold is shown.
Sometimes, when energy is added to an atom, electrons can absorb
enough energy to “jump” to a higher energy level. When they fall back to
their normal energy level, they
release light in a characteristic frequency.
It is important to note that some energy levels can overlap.
In fact, each energylevel is subdivided into smaller
regions called Orbitals.
Some orbitals in the thirdenergy level may have higher energy than some in the fourth and so on.
Scientists have found out exactly which orbitals are occupied, and by
how many electrons, inall 114 elements.
The Bohr Model of the Atom• Electrons circle the atom
only in allowed paths, or orbits.
• Orbits have a definite, fixed energy level.
• Energy level is lowest in the orbit closest to the nucleus.
• Energy of electrons is higher in orbits successively farther from the nucleus.
• Analogy: Rungs of a ladder – you cannot stand between the rungs!
The Bohr Model of the Atom• While in a given orbit,
electrons can neither gain nor lose energy – but can move to higher energy level by gaining energy in some form.
• When the electrons drops back down to its original, lower energy level, it emits a photon of light (of a characteristic color for that particular element.)
Arrangement of Electrons in
Atoms(The Race Around the Track)
Electron Configurations
Electron ConfigurationsDescribing the arrangement of electrons
in an atom
Carbon1s22s22p2
main energy
level (n)energy
sublevel (l)
Number of electrons
in sublevel
Sample ProblemBoron
1s22s22p1
How many electrons are present
in a boron atom?Atomic number for boron?Orbital notation for boron?
Sample ProblemBoron
1s22s22p1
# e- : 2+2+1=5 e-
Atomic number: #p+=#e-=5
Sample Problem
Boron 1s22s22p1
Orbital notation:
_____ _____ _____ _____ _____ 1s 2s 2px 2py 2pz
The Relative
Energies of
Orbitals
Energy level
overlap.
Electrons
Accommodate
d in
Energy Levels
and
Sublevels
Writing Electron
Configurations
Relative Energy of Orbitals
The Basic Chemical Laws
• The following Chemical Laws can be
explained on the basis of Dalton’s
Atomic Theory:
–The Law of Conservation of
Mass
–The Law of Definite Proportions
–The Law of Multiple
Proportions
The Law of Conservation of MassMass is neither created nor destroyed during ordinary chemical reactions or
physical changes.
The number of oxygen atoms
and the number of
carbon atoms are the same before and after each reaction.
The Law of Definite ProportionsA chemical compound contains the same
elements in exactly the same proportions by mass regardless of the size the sample or source
of the compound – given compound always composed of the same combination of elements.
The Law of Definite Proportions
• Example: Table salt is always table salt.
• No matter how many or how few NaCl crystals you look at, the mass % of sodium and chlorine remains unchanged.
– (NaCl) is always 39.34% Na by mass and 60.66% Cl.
The Law of Multiple Proportions
If two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a
certain mass of the first element is always a ratio of small whole numbers.
Example:Carbon monoxide: CO ratio of C to O is 1:1Carbon dioxide: CO2 ratio of C to O is 1:2
Activity
Customize Your Own Periodic
Table
Periods and BlocksRemember, elements
are arranged in vertical columns, or groups, based upon
similar chemical properties.
Periods and BlocksElements are also
arranged in horizontal rows, or periods, based
upon the number of electrons that can occupy the sublevels being filled
in that period.(see Table 5-1, page 128)
Periods and BlocksThere are 18
Groups and 7 Periods in the
modern Periodic Table
Periods and Blocks• Determining the period of an
element from its electron configuration– Example) Arsenic (As)
– [Ar]3d104s24p3
– Highest energy level being filled is 4, therefore 4th Period.
Periods and Blocks• The Periodic Table is divided into 4
blocks:
– s-block– p-block– d-block– f-block
Periods and Blockss-block Elements
• Group 1– ns1
– Metals– Reactive - single electron in outer shell– Alkali metals– Silvery, soft– Not found in nature as free elements,
stored in kerosene
Periods and Blockss-block Elements
• Group 2– ns2
– Alkaline-earth metals– Harder, denser and stronger than
Group 1– Also not found in nature as free
elements.
Periods and BlocksHydrogen and Helium
• Hydrogen– ns1, but doesn’t share properties with
Group 1 ( or any other Group) – it is unique.
• Helium– ns2, part of Group 18 – stable, non-
reactive.
Periods and Blocksd-block Elements
• Filled after 4s• 5 orbitals, 10 electrons• n – 1• Metals - shiny• Transition elements• Less reactive than Groups 1 and 2.
Periods and Blocksp-block Elements
• Groups 13-18, except He.• p filled only after s in a sublevel.• Together with s-block elements are
called main-group elements.• ns2,np1-6
• Electrons in highest energy level = Group number – 10.– Ex. Group 17 -10 = 7 electrons in outer shell.
• Metals, metalloids and nonmetals
Periods and Blocksp-block Elements
• Group 17 – halogens– Most reactive nonmetals (7 e- in outer
shell.– React with metals to form salts.– Solids, liquids and gases.
• Metalloids– Brittle solids– Intermediate properties
The Noble Gases In 1868, Helium was discovered, and
in 1894, Argon. Both displayed a total lack of
chemical reactivity. Ramsey proposed a new group to fit
these elements into, and it became known as Group 18.
The rest of the Noble Gases, Kr, Xe and Rn, were discovered by 1900.
Periods and Blocksf-block Elements
• Lanthanides– 14 elements– Located between Groups 3 and 4 in
the 6th Period.– Involved in filling the 4f sublevel.– 7 f-orbitals with a capacity of 14 e-.– Shiny metals similar in reactivity to
Group 2.
Periods and Blocksf-block Elements
• Actinides– 14 elements– Located between Groups 3 and 4 in
the 7th Period.– Involved in filling the 5f sublevel.– 7 f-orbitals with a capacity of 14 e-.– All radioactive
Section 5-1History of the Periodic Table
History of the Periodic Table1860
More than 60 elements had been discovered – all their properties had to be learned
No method for determining atomic mass or number of atoms of an element in a compound – different masses were being used for the same element!
Mendeleev and Chemical Periodicity
Wanted to organize elements Listed names, atomic masses and
properties of known elements on cards and looked for patterns.
Noticed that when elements were arranged in order of increasing atomic mass, certain similarities in their chemical propertied appeared at regular intervals.
This repeating pattern is referred to as periodic.
Mendeleev and Chemical Periodicity
In 1869, Mendeleev created a table which grouped elements with similar properties together.
Made a few exceptions to the order of increasing atomic mass in order to create groups with similar chemical properties.
Mendeleev and Chemical Periodicity
This procedure left several empty spaces in the table – in 1871, he boldly announced three would be filled.
By 1886, all three elements had, in fact, been discovered – with properties very similar to those that Mendeleev predicted!
Mendeleev and Chemical Periodicity
The success of Mendeleev’s predictions persuaded most chemists to accept his Periodic Table and earned him the credit as the discoverer of the Periodic Law.
Mendeleev and Chemical Periodicity
However, two questions remained: Why could most of the
elements be arranged in order of increasing atomic mass but a few could not?
What was the reason for chemical periodicity?
Moseley and the Periodic Law
In 1911, Moseley announced that the elements in the Table fit into patterns better when they were arranged in increasing order according to the number of protons in the nucleus.
Moseley and the Periodic Law
Led to the modern definition of atomic number and the recognition that atomic number, not atomic mass, is the basis for organization of the Periodic Table.
Moseley and the Periodic Law
Today, Mendeleev’s Principle of Chemical Periodicity is correctly stated in what is known as the Periodic Law.
– The physical and chemical properties of the elements are periodic functions of their atomic numbers.
– In other words, when the elements are arranged in order of increasing atomic number, elements with similar properties appear at regular intervals.
The Modern Periodic Table
New elements have been discovered and many have been synthesized since Mendeleev’s time.
Today, the Periodic Table is an arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group.
Periodicity Can be observed in any group of
elements in the Periodic table. Example – Noble Gases (non-
reactive) of Group 18.– He – atomic number 2– Neon – 10– Ar – 18, Kr – 36, Xe – 54, Rn – 86.– Periodicity: 8, 8, 18, 18, 32
Periodicity Example – Group 1 (solid,
silvery metals).– Li – atomic number 3– Na – 11– K – 19, Rb – 37, Cs – 55, Fr –
87.– Periodicity: 8, 8, 18, 18, 32
Periodicity Example – Starting with
first member of Groups 13-17.– Periodicity: 8, 18, 18, 32
The Aufbau
PrincipleAn electron
occupies the lowest
energy orbital that can receive
it
ExampleThe 4s orbital is
filled before the 3d
The Pauli Exclusion Principle
No two electrons in
the same atom can have the
same set of four
quantum numbers.
• Electrons occur in pairs with opposite spins
Hund’s Rule
Orbitals of equal energy are each occupied by one electron before any orbital is occupied by a
second electron, and all electrons
in singly occupied orbitals
must have the same spin.
_____ _____ _____2px 2py 2pz
Hund’s Rule
Orbitals of equal energy are each occupied by one electron before any orbital is occupied by a
second electron, and all electrons
in singly occupied orbitals
must have the same spin.
All students will try to get their own seat
on a separate row until all rows are
filled with one student. Only then will they begin to
double-up.
A school bus after a rainstorm
•The elements of Group 18
•He, Ne, Ar, Kr, Xe, Rn, •Outer main energy level fully occupied, in most cases, by eight electrons
Noble Gas Configuration
Noble Gas Configuration
H: 1s1
He: 1s2
Li: 1s22s1
[He]2s1
Noble Gas NotationNe: 1s22s22p6
[He] 2s22p6
Na: 1s22s22p63s1
[Ne] 3s1
Ar: [Ne]3s23p6
K: [Ar]4s1
• The mole is the SI unit for the amount of substance.
• A mole is the amount of a substance that contains as many particles as there are atoms in exactly 12g of carbon 12.
• 6.022 136 7 x 1023
–Ex.) 12g of C-12 contains 6.022 136 7 x 1023 carbon-12 atoms.
• This is Avogadro’s Number – the number of particles in exactly one mole of a pure substance.
• Rounded to 6.022 x 1023.
The Mole
• The mass of one mole of a pure substance is called the molar mass of that substance.
• A molar mass of an element contains one mole of atoms.–Ex.) 4.00g of He, 6.946 of Li and 200.59g of Hg all contain a mole of atoms.
Molar Mass
To two decimal places, what is the
relative atomic mass and the molar mass
of the element chlorine, Cl?
Moles and Molar Mass
Sample Problems
Determine the mass in grams of the
following:3.00 mol S
3.01 × 1023 atoms F
Moles and Molar Mass
Sample Problems
Determine the amount in moles of
the following:12.15 g Ca
1.50 × 1023 atoms Br
Moles and Molar Mass
Sample Problems
Determine the number of atoms in
the following:2.50 mol Fe
1.50 g P
Moles and Molar Mass
Sample Problems
VideoAtoms
The Building Blocks of Matter
Gizmos LabDensit
y
LabCalculating
Density
LabDensit
y of Solids
Lab The Law of Conservation
of Mass
Lab How Sweet It Is
VideoAtoms
The Building Blocks of Matter
LabCounting Atoms
(page 115)
Classify the following changes as either physical or chemical.
MeltingDigestingBurningFreezingRustingCutting
Condensating
Bell Ringer 9-17-09
How would you determine if an object
will sink or float in water without actually
dropping it into the water?
Bell Ringer 9-21-09
A sample liquid is cooled from 150°C to 30°C, causing the liquid to change into a solid. Which of the following
has occurred?Chemical composition has changed.
A physical change has occurred.A new compound has formed.
Evaporation of a solvent has occurred.
Bell Ringer 9-22-09
A student puts a 45.7 gram sample of a solid into a 100 mL graduated cylinder that contains 50.0 mL of water. The object raises the water level to 82.5 mL. What is the density of the object?
Bell Ringer 9-24-09
No Bell Ringer TodayPick up a calculator and your
Scantron (green side) on your way in.
Take out all of the Reference Sheets that you want to use
on today’s test.You need a pencil.
Bell Ringer 9-25-09
Some students investigate the rusting rate of four metals in saltwater. To best find the rusting rates,
the students should measure the masses of the metals before the investigation and at
A. the same time and day during each week of the investigation
B. different times and days during each week of the investigation
C. any time during the first week of the investigation
D. one randomly selected time during the investigation
Bell Ringer 9-28-09
In addition to a hot plate and beakers, which of these items are needed to test the hypothesis
below?A. Test tube, barometer, thermometerB. Balance, thermometer, hand lensC. Stopwatch, microscope, test tubeD. Thermometer, stopwatch, balance
Bell Ringer 9-29-09
A student uses a hot plate, a thermometer,and a stopwatch to investigate the rate at
which a metal object conducts heat. To ensurethe most reliable results, which of the
following should the student do?A. Perform a second investigation using different
toolsB. Use several thermometers to measure
temperatureC. Develop a hypothesis before starting the
investigationD. Repeat the entire investigation several times
Bell Ringer 10-2-09
Define the terms “mass” and
“conservation.”
Bell Ringer 9-30-09
The table shows some properties of four different substances. The picture shows a solid sphere of one of the four substances in a water-ethanol solution (D = 0.9199
g/mL). The sphere is most likely composed of which substance?
Bell Ringer 9-23-09
Who made the following contributions to the understanding of the atom?Thought matter was continuous
First thought matter was made of tiny particles
First modern atomic theoryDiscovery of the electronDiscovery of the nucleus
Structure of the electron cloud
Bell Ringer 10-5-09
What type of atom is
shown in the picture? How do you know?
Bell Ringer 10-6-09
Draw a simple picture of a
sodium atom.
Bell Ringer 10-7-09
Write the electron configuration notation, isotopic notation, and
hyphen notation for the following elements.
H, C, O, Na, Cl
Bell Ringer 10-8-09
Please answer the following questions concerning the Periodic
Table.What do zinc, iron, and sodium
have in common?What do oxygen, carbon, and hydrogen have in common?
Bell Ringer 10-9-09
1. What do the elements in a group have in common?
2. Briefly describe the following rules:• Aufbau Principle
• Pauli Exclusion Principle• Hund’s Rule
3. Write the Noble Gas notation for the element phosphorus
Bell Ringer 10-13-09
How many moles are there in
135.98 grams of iron?
Bell Ringer 10-14-09
List three things that the number
6.022 x 1023 represents.
Bell Ringer 10-16-09
1. It is Avogadro’s number
2. It is the number of particles in a mole of a substance.
3. It is the number of particles in one molar mass of a substance.
Bell Ringer 10-16-09
No Bell Ringer TodayPick up a calculator and a
Scantron (blue side) on your way in.
Take out your customized Periodic Table (page 109)
You need a pencil.
Bell Ringer 10-19-09