monday october 4, 2010

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.

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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.


Together, protons, neutrons and electrons

are referred to as subatomic particles.


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.


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.


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!


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.


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.


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.


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


Sample Problems

Determine the amount in moles of

the following:12.15 g Ca

1.50 × 1023 atoms Br


Sample Problems

Determine the number of atoms in

the following:2.50 mol Fe

1.50 g P


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?


List three things that the number

6.022 x 1023 represents.


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.


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.


monday october 4, 2010

Documents

physical change

independent change

independent variable

chemical identity

liquid phaseparticles

chemical changeswhen

atoms of different elements

lowest density