BELL RINGER

BELL RINGER

What subatomic particle is not located in the

nucleus?

Atomic History Research

Atomic History Research

Chapter 3

Chapter 1

Chapter 5

Task: • Design a timeline to show the events which

contributed to the development of the atomic model.• Your timeline must be drawn to scale.

1. Democritus2. Dalton3. JJ Thomson 4. Robert Millikan5. Rutherford6. Chadwick7. Bohr8. Schrödinger

9. Planck10. Goldstein

Timeline Activity

BELL RINGER

What are the nucleons (things in

the nucleus)?

1. Who did the gold foil experiment?2. Who first named an atom?3. According to Bohr, where are

electrons located?4. Draw an atom according to

Democritus.5. Who discovered the electron?

A. Ancient Greece (2000+ years ago)

Democritus - believed that matter could not be continuously divided- Matter consists of small indivisible particles“Atomos” = Atom indivisible

Particles are in continuous motionFour elements make up all matter and energy

Earth, Wind, Water, Fire!No scientific evidence to show this.

- Aristotle did not agree his teacher

B. Dalton’s Atomic Theory - 1803

1. All matter is composed of small particles which cannot be broken down (atoms) same as Democritus

2. All atoms of the same element are identical in size, mass and properties. Atoms of different elements are different in size, mass and properties

3.Atoms of different element combine in simple ratios to make compounds 4. In chemical reactions, atoms are combined, separated, or rearranged (No atoms are created or destroyed)

So at this point, we believe that an atom is like a small solid ball of matter that cannot be split up

H2S PbO2

Hydrogen Sulfur

But there are different ones

Some parts of Dalton’s theory were wrong: AMENDMENTS atoms are divisible into smaller particles

(subatomic particles) atoms of the same element can have

different masses (isotopes) Matter can be lost - Nuclear

C. J.J. Thomson - 1897

Experimented with cathode raysUsed electric field to show that cathode rays are negatively charged particles

DISCOVORED THE ELECTRONAfter discovery of the proton, Thomson assumed an atom was a mixture of + and – charged particles, all mixed up

Plum-Pudding Model+ - + -- + -

- + - +

D. Rutherford Ernest Rutherford wanted to determine what an atom looked like.Fired (+) charged alpha particles at a very thin piece of gold (Gold foil)Put a screen behind the foil to determine what happens to the rays

Gold foil

Screen

Most of the rays went straight through the foilSome rays deflectedA very few rays came straight back

Radioactive source

Click on me!!!

Rutherford explained this by stating thata. Atoms have mostly empty space

This is why most rays went straight throughb. There must be a dense positive center to an atom

This is why the positive rays deflected. (Positive rays are repelled by positive charged objects)

Later experiments showed that electrons exist in the space between nuclei

- - - - - -

+

Rutherford model

includes all particles inside atom proton electron neutron

charge on protons and electrons are equal but opposite

to make an atom neutral, need equal numbers of protons and electrons

number of protons identifies the atom as a certain element

protons and neutrons are about same mass

electrons are much smaller

# protons = atomic number# electrons = # of protons (for now)# neutrons =

mass number– atomic number

26

4

11

3

p n e4 3

1112

5 4

30 26

Li37

Na1123

Be49

Fe2656

BELL RINGER

Give the p, n, and e in a neutral atom of

Silver.

22

54

80

17

p n e

18 17

121 80

77 54

26 22

Cl17

Hg201

Xe

X22

Nucleus: contains protons

and neutrons takes up very little

space Electron Cloud:

contains electrons takes up most of

space

e- e-

E. Bohr - looked at the arrangement of electronsElectrons exist in definite areas around the nucleus

Further from the nucleus, an electron has more energy

Electrons can gain energy and “jump” to higher levels

They can then give off the energy as they jump back down

Energy levels are numbered 1,2,3,4,5,6,7 • With 1 being closest to the nucleus and

having the least amount of energy

All atoms have the same types of energy levels

nucleus

e-Energy levelse-

3 2 1

Planetary model

+ - - -

- - -

F. Wave Mechanical ModelAka – ‘Electron Cloud’

Electrons are not in circular orbits, but exist in specific spaces around the nucleus

Pattern is random, unpredictable• most dense near nucleus

levellevel

Energy levels contain sublevels

nucleus

Dr. Wave Mechanical

Modified Bohr’s model

Review of Atoms

Democritus

Dalton

Thompson

Rutherford

Bohr

Wave Mechanical

Electron Location• Located in energy levels outside of the nucleus• The closer to the nucleus = less energy • The farther away from the nucleus = more energy

Electrons are located in energy levels or shells. There are a bunch of energy levels and each level can “fit” only a limited number of electrons.

2 e-8 e-18 e-32 e-

2n2

Energy level 1 can have -Energy level 2 can have -Energy level 3 can have -Energy level 4 can have -

Electron Location

Where ‘n’ represents the energy level

Bohr DiagramsGives the location and the number of the p, n, and e.

p=n=

Draw the Bohr diagram for Oxygen:

8

8

Valence e- = 6

Answer

p=n=

9

10

Valence e- = 7

BELL RINGER

What did Rutherford contribute to the

development of the atom?

1. Ge2. Manganese3. As4. Phosphorus5. Ti

6. Sodium7. Cr8. Krypton9. Be10.Boron

atoms of the same element with different numbers of neutrons

most elements exist as a mixture of isotopes Disproves Dalton’s theoryWhat do the Carbon isotopes below have in

common? What is different about them?

sum of the particles in nucleus = #p + #n This is a whole number!!!

How many protons do each of the hydrogen atoms below have?

since masses of atoms are so small, it is more convenient to use relative atomic masses instead of real masses

to set up a scale, we have to pick one atom to be the standard

since 1961, the carbon-12 nuclide is the standard and is assigned a mass of exactly 12 amu (=atomic mass unit)

REFERENCE TABLES

atomic mass unit (amu)- one is exactly 1/12th of the mass of a carbon-12 atom

mass of proton= 1.007276 amu = 1 amu mass of neutron= 1.008665 amu = 1amu mass of electron= 0.0005486 amu = 0

amu

weighted relative atomic masses of the isotopes of each element

each isotope has a known natural occurrence (percentage of that elements’ atoms)

An element has three main isotopes with the following percent occurances: #1: 19.99244 amu, 90.51% #2: 20.99395 amu, 0.27% #3: 21.99138 amu, 9.22%

Find the average atomic mass and determine the element.

=20.179 amu

Naturally occurring copper consists of: Cu-63 Cu-65

Actual Mass 62.929amu 64.927amu

Percent Abundance

Relative abundance

Relative Mass

69.71% 30.83% 100.54

.6971 .3083 1.0054

43.87 20.02 63.89

There are two isotopes of Silver, Ag-107 and Ag-109. 52% of the isotopes are Ag-107, what is the average atomic mass of silver?Ag-107Ag-109

52%48%

==

5564523210796

÷100=107.96

BELL RINGER

Calculate the average atomic mass of Sulfur.

Isotope AMU Natural Abundance

32S 31.97 94.93%33S 32.97 0.76%34S 33.97 4.29%36S 35.97 0.02%

32.06 amu

Ions So far we have only talked about electrically

neutral atoms, atoms with no positive or negative charge on them. 

Atoms, however, can have electrical charges – They can gain/lose e-.  Some atoms can either gain or lose electrons

The number of protons never changes in an atom. 

Ions  If an atom gains electrons, the atom becomes

negatively charged.  If the atom loses electrons, the atom becomes

positively charged (because the number of positively charged protons will exceed the number of electrons). 

An atom that carries an electrical charge is called an ion. 

Ions  Listed below are three forms of hydrogen; 2

ions and the electrically neutral form.

H+ : a positively charged hydrogen ion H : the

hydrogen atom

H- : a negatively charged hydrogen ion

Ions Neither the number of protons nor neutrons changes

in any of these ions, therefore both the atomic number and the atomic mass remain the same.

H+ : a positively charged hydrogen ion

H : the hydrogen atom

H- : a negatively charged hydrogen ion

IonsIdentify the number of subatomic

particles in the following ions:

A.) Na+ B.) F- C.) O-2

p

n

e

11

12

10

9

10

10

8

8

10

IonsIdentify the number of subatomic

particles in the following ions:

A.) Mg+2 B.) Br- C.) K+

p

n

e

12

12

10

35

45

36

19

20

18

Ions/IsotopesPRACTICE PROBLEMS

When subjected to a flame, solutions containing certain metals have characteristic colors corresponding to the energy released when excited electrons return to lower energy levels.

BELL RINGER

Which is the electron configuration of an atom in the excited state?

1)2-8-2

2)2-8-1

3)2-7-1

4)2-8-3

The above is an example of a ground state electron configuration

(=the configuration on your R.T.’s)

Each electron in an atom has its own distinct amount of energy. Electrons in the first energy level have the lowest potential energy since they are located closest to the nucleus.

Ground State e- Configuration for Ne

2-8

As an electron gains a specific bunch of energy, the electron “jumps” to a higher energy state (excited state).

p=n=

10

10p=n=

10

10

Excited State e- Configuration for Ne

2-7-1

Gives off Ground State

e- Configuration for Ne2-8

How is light produced?

p=n=

10

10p=n=

10

10

Excited State e- Configuration for Ne

2-7-1

Releases nrg

Absorbs nrg

When an electron returns from a higher

energy state to a lower energy state, a specific amount of

energy is given off --> RELEASED

Each element gives off a certain color or spectrum

of colors.

You can identify unknown elements by the color of light that they give off.

Bohr Animation

BELL RINGER

Draw the Bohr diagram for a F-1 ion.

BELL RINGER

Identify the number of p, n, and e in the following:

13717

Cl

Spectroscopy

The energy emitted is in the form of radiant or light energy which corresponds to a bright-line spectrum. Each element has its own signature or bright-line spectrum.

There are several kinds of spectra, such as: continuous & bright line.A continuous spectrum is, as the name implies, a parade of all the colors from the deepest red to the ultraviolet - of which the rainbow in the sky is a good example. 

In the laboratory, a continuous spectrum can be produced by heating a solid - Light from the

electric lamp filament, for example, produces such a spectrum.

When light emitted by a gas through which an electrical discharge is passing produces a spectrum consisting of a few isolated parallel lines, it is known as a "bright line spectrum"  

The characteristic color of neon signs is due to bright red and orange lines in its spectrum. The typical color of neon signs is due to the great intensity of the red and orange lines.

Element X

Element Y

Elements X and Y combined

3 different electron jumps

A group of elements would create a combination of spectral lines

Notice how the combination of X and Y is just a combination of the individual spectral lines?

Some Atomic Emission Spectra

Hydrogen

Mercury

Argon

Helium

It should be carefully noted that each element always gives the same pattern of lines.  Each element, so to speak, has its own fingerprints, possessed by no other element.  This fact is utilized in chemical analysis and in many other applied fields.

BELL RINGER

Identify the number of electrons and neutrons in the following:

1)Ti +3

2)S-2

Unknown

What element is the unknown?

Atomic Theory

Around the World

Atomic History

DEMOCRITUS named the most basic particle

atom- means “indivisible

Atomic History

1. Atoms of same element have the same size, mass, and properties

2. Atoms can’t be subdivided, created or destroyed

3. Atoms of different element combine in whole number ratios to make compounds

4. In chemical reactions, atoms are combined, separated, and rearranged.

DALTON

Atomic History

Some parts of Dalton’s theory were wrong: atoms are divisible into smaller particles

(subatomic particles) atoms of the same element can have different

masses (isotopes) Most important parts of atomic theory:

all matter is made of atoms atoms of different elements have different

properties

DALTON

Atomic HistoryRUTHERFORD

‘Gold Foil Experiment’ Atom is mostly empty space Small, hard, dense positive part = NUCLEUS

Atomic HistoryJJ THOMSON

discovered the e-

Atomic HistoryNEILS BOHR Electons in ‘orbit’

protons in nucleus

Atomic HistoryMODERN MODEL

protons in nucleusElectrons in an orbital – most probable location

Atomic HistorySUMMARY

What we know about the atom has been the work of many scientists over thousands of years!

BELL RINGER

How much heat energy in joules is released by 25.0 grams of water when it is cooled from

75.2ºC to 31.9 ºC? Get the formula from Reference Tables

q = mcΔT

q = 25.0g (4.18J/g•ºC) 43.3ºC

q = 4525 J