S.MORRIS 2006

Study of matter- 2000 years ago!!Aristotle and Democritus were 2 Greek philosophers who gave us some basic ideas. Aristotle- four elements- Earth, air, fire, water!!Democritus- if you keep cutting matter into smaller pieces, you can eventually cut no more- this INDESTRUCTIBLE INDIVISIBLE piece is called ATOMOS (meaning indivisible in Greek)

HISTORY OF THE ATOMHISTORY OF THE ATOM

John “4 Good Ideas” DALTON

Matter is made up of tiny spheres.

Dalton named them:ATOMSATOMS (atomos term

given by Democritus)

Dalton’s 5 ideas about “ATOMS”:

1. Everything is made of atoms

2. All atoms of the same element are identical

3. Atoms of different elements are different

4. Atoms can team up to make compounds

5. Atoms can’t be broken into smaller parts

HISTORY OF THE ATOMHISTORY OF THE ATOM

Joseph “I shall name you ELECTRON!!” Thomson

Found that atoms could

sometimes eject a really

small negative particle

which he called anELECTRONELECTRON

JUST LISTEN: JT’s Experiment• Put + and –

plates near “laser” and it was attracted to the positive.

• What charge was the stream of the laser?

Thought atoms were filled with a positively

charge goo that balanced the electron’s

negative charge (wrong!)

like plums surrounded by pudding

Thomson’s (wrong) “PLUM PUDDING” MODEL IDEA:

Ernest “IT’S A NUCLEUS!” Rutherford

Shot helium atoms at a piece of

gold foil which was a few atoms

thick.

About 1 in 10,000 bounced off

something in the gold foil!

Ernest “It’s a nucleus!” Rutherford

gold foil

helium nuclei

A few of the helium atoms bounced off

something.

helium nuclei

If the “Plum Pudding” model were true.

The actual result: some bounced back like they hit something solid!

Gold foil!

Hel

ium

Nu

clei

Hel

ium

Nu

clei

“Nucleus” Rutherford’s gold foil evidence

showed him atoms have a nucleus in the

center.

He determined that the nucleus had a

positive charge, and that the negative

electrons were attracted to the positive

nucleus.

However, this was not the end of the story…

Niels “Orbits” Bohr

• Bohr figured out that the electrons were

in orbits (like planets orbiting the sun).

• Each orbit holds a set number of

electrons.

•Noticed that elements absorbed and emitted the same colors.

•Concluded electrons absorb energy to “jump” up levels and lose the same energy when they “fall” back down.

Bohr’s thinking

James “I shall call you NEUTRON!” Chadwick • Shot radiation into wax. Saw:

1) Radiation didn’t bend toward + or

– plates, so neutrons must have

no charge (neutral).

2) The radiation made atoms eject a

proton—so this particle must

have mass too!

• He named the particle the

NEUTRON.

Just Listen: Jimmy’s Experiment

• Because the radiation forced

protons out of the atoms, the

radiation was made of heavy

particles! Neutrons have

mass!

Build a MNEMONIC!

• D ogs

• T urn

• R owdy

• B y

• C lapping

The Current Model of the Atom• Electron Cloud Model:

– Nucleus: p+ and no

– Electron cloud: surrounded by e- that move so fast they look like a blur (think fan blades)

•E- are more likely found closer rather than farther away

Guiding questions:

• Who discovered which parts of the atom?

• In what order were the things discovered?

ATOM (Dalton) with ELECTRONS (Thomson)

in ORBITS (Bohr)

+N

N

+-

-

proton

electron

neutron

Orbit/

Shell

Atomic Structure: Where do they live?Protons (p+): In nucleus.

Neutrons (n0): In nucleus with protons.

Electrons (e-): outside nucleus, zooming around

SUBATOMIC PARTICLE CHARGE AND MASS:SUBATOMIC PARTICLE CHARGE AND MASS:

Particle

proton

neutron

electron

Charge

Positive

Negative

No charge

1

1

0

Mass

Mass is measured in Atomic Mass Units (AMUs)

Positive Proton

Neutral Neutron

(negative electron: e- )

Flag Practice: Charges, Masses, Location

Guiding Questions

• What are the three parts of the atom?

• Where are the subatomic particles located?

• What are the charges of the subatomic particles?

• What are the masses of the subatomic particles?

• Different amounts of protons change what atom it is.

Purpose of Subatomic Particles

• Different amounts of neutrons make atoms unstable and radioactive (they shoot particles out!)

– Isotopes: atoms with different amounts of neutrons.

• Different amounts of electrons make atoms have different charges.

– Ions: atoms with a charge (+ or -)

Atoms are neutral

ATOMS ARE NEUTRAL

• If atoms are neutral, the number of positive protons must be ___?___ the number of negative electrons

ATOMS ARE NEUTRAL!!!!

The # of P = The # of e-

The # of e- = the # of p

ATOMIC STRUCTUREATOMIC STRUCTURE

The # of protons in an atom

The # of protons + neutrons in an atom

HeHe22

44 Atomic Mass

Atomic Number

number of protons = number of electrons.

Why??

Mr. Addem Proneumass

Get it??? Add them…Addem….

Pro + Neu = Mass

The Atomic Mass• The Atomic Mass must be rounded because

there are different isotopes of every atom.• Every isotope has a different mass and is

present in different amounts on the earth.• To calculate the atomic mass, we consider

how much each isotope weighs and which form is most common on the earth.– Ex: Atomic Mass of Boron = 10.81 AMU. – How many neutrons on average?

Let’s Label our Periodic Table!• Find hydrogen.

• Circle the atomic number.

• Put a rectangle around the atomic mass.

What is hydrogen’s…

atomic number

atomic mass

# of p

# of e

# of n

Symbol Atomic #

Atomic Mass

# of p+ # of e- # of n0

Au

Ca

F

Na

Rn

Pb

K

Make the following table in your notes…

Homework Activity• Spell out a message or phrase to your assigned

partner.

• Create an answer key to give to me (name, A.M., A.N., P, e-, N for each element)

Assigned partner has to find:

• The element name

• Atomic Mass for each element

• Atomic Number for each element

• P, N, and e-

Atomic Mass vs Number Homework

• Worksheet

• Worksheet

• And worksheet some more

• RAFT activity? Or a raft after configuration notes?

QUIZ

GUIDING QUESTIONS

• How is atomic mass calculated?How do you get the atomic number?

• Why must the number of protons and electrons be equal?

ATOMIC STRUCTUREATOMIC STRUCTURE

Electrons are arranged in Energy

Levels (a.k.a Shells/Orbits) around the

nucleus (Bohr’s idea!)

•1st shell max of 2 electrons

•2nd shell max of 8 electrons

•3rd shell max of 8 electrons

(Sneak Preview)

• The electrons in the outermost shell are called “valence electrons” and are super important for determining how atoms bond.

• Way more important than regular electrons.

•WAY MORE.

Bohr DIAGRAMSBohr DIAGRAMS

Elements are represented by Dots or

Crosses to show electrons, and circles to

show the shells (orbits) of electrons

Nitrogen N XX X

X

XX

X

N7

14

Bohr DIAGRAMSBohr DIAGRAMS

Draw the Bohr diagrams for the following elements;

O Cl8 17

16 35a) b)

O

X

XX

X

X

X

X

X

Cl

X

X

X

X X

X

XX

X

X

X

X

X

XX

X

X

X

SUMMARY:SUMMARY:1. The Atomic Number of an atom = number of

protons in the nucleus.

2. The number of Protons = Number of e-

1. The Atomic Mass of an atom = number of

Protons + Neutrons in the nucleus.

1. Electrons orbit the nucleus in shells.

2. Each shell carries a set number of e-’s

Symbols

• Hydrogen H• Helium He• Lithium Li• Mercury Hg• Lead Pb• Carbon C• Nitrogen N• Oxygen O

Symbols

• Fluorine F• Neon Ne• Sodium Na• Magnesium Mg• Gold Au• Tin Sn• Iodine I• Aluminium Al

Symbols

• Sulfur S• Silicon Si• Phosphorus P• Chlorine Cl• Potassium K• Calcium Ca• Iron Fe• Copper Cu

Symbols

• Cobalt Co

• Nickel Ni

• Zinc Zn

• Arsenic As

• Silver Ag

• Radon Rn