Chapter 1Chapter 1Activity 4: Are Atoms Divisible?Activity 4: Are Atoms Divisible?

(1st Verse)They’re tiny and they’re teeny,Much smaller than a beany,They never can be seeny,The Atoms Family. (Chorus)(2nd Verse)Together they make gases,And liquids like molasses,And all the solid masses,The Atoms Family (Chorus)

(Chorus)They are so small.(snap, snap)They’re round like a ball.(snap, snap)They make up the air.They’re everywhere.Can’t see them at all.(snap, snap) 

(3rd Verse)Neutrons can be found,Where protons hang around;Electrons, they surroundThe Atoms Family. (Chorus)

(4th verse)The periodic table,It isn’t just a fable;You’ll read it when your able;The Atoms Family (Chorus) (Chorus) 

DemocritusDemocritus1.Greek philosopher

2.He thought atoms were uncuttable

3. Therefore: Atoms are indivisible particles

Atomos—Greek meaning ‘indivisible

Ancient Greece

470-380 B.C.

John Dalton—late 18John Dalton—late 18thth century century

1. What are atoms? 1. What are atoms?

2. Do Carbon atoms differ from 2. Do Carbon atoms differ from Oxygen atoms?Oxygen atoms?1766-

1834

Dalton’s Atomic Model:

Hard, indivisible sphere

Yes

https://www.youtube.com/watch?v=iVk0yf6MqL4

HAS THIS EVER HAPPENED TO YOU?

Are there things inside the atom?Are there things inside the atom?

YES!YES!Subatomic particles- Subatomic particles-

particles that are smaller particles that are smaller than the atomthan the atom

ee-- p p++ n n00

Discovery of electron (e-)Discovery of electron (e-)

J.J. Thomson

1856-1940

Cathode ray tube

Discovered the electron in 1897.

• Identified a glowing beam of particles that traveled through a chamber of gas when exposed to an electrical current.

-This beam (cathode ray) was attracted to positive charges and repelled by negative charges.-Thomson concluded the beam must be composed of negatively charged particles. These came to be known as electrons.

Thomson’s Atomic ModelThomson’s Atomic Model

““Plum Pudding” ModelPlum Pudding” Model

Negative electron plums are floating around in a sphere of positive pudding.

ELECTRONSEMBEDDED WITHIN

POSITIVE CHARGE

Discovery of the NucleusDiscovery of the Nucleus

Ernest Rutherford

1871-1937

Rutherford’s Au foil ExperimentRutherford’s Au foil Experiment

“+” charge

Rutherford’s Rutherford’s experimentexperiment

-Discovered the Nucleus (through the Gold Foil Experiment)

-Discovered that the atom is mostly empty space

-Alpha particle: a positively charged particle, consisting of two protons and two neutrons (helium nucleus).

Rutherford’s Nuclear AtomRutherford’s Nuclear Atom

PositiveNucleus

Negative electrons

surround nucleus amidst lots of empty space.

Discovery of the protonDiscovery of the proton

Eugen GoldsteinEugen Goldstein

In 1886, Goldstein observed rays in a cathode ray tube that traveled oppositely than the electrons previously discovered.

James ChadwickJames Chadwick

1. Discovered the neutron in 19321. Discovered the neutron in 1932

2. This subatomic particle is heavy enough to 2. This subatomic particle is heavy enough to split a nucleussplit a nucleus

3. Led the way to the creation of the atomic 3. Led the way to the creation of the atomic bombbomb

ProtonsProtonsLocated in nucleusLocated in nucleus

Determine which element (DNA)Determine which element (DNA)

# of protons = # of protons = atomic numberatomic number equal to # of electrons in a neutral atomequal to # of electrons in a neutral atom

Ch 1: Ch 1: Activity 4Activity 4

LETS HAVE SOME PRACTICELETS HAVE SOME PRACTICE

6

CCarbon

12

Atomic Number (Protons)

Mass Number(Proton+Neutrons)

Element Symbol

Element Name

126

Mass Number(Protons+Neutrons)

Atomic Number(Protons)

C

Mass NumberMass Number

Almost all the mass of an atom comes Almost all the mass of an atom comes from protons & neutronsfrom protons & neutrons

# Protons + # Neutrons = mass # Protons + # Neutrons = mass numbernumber

Atomic # Atomic # = # of protons (P)= # of protons (P)

# protons = # electrons in an atom# protons = # electrons in an atom

Mass # Mass # = number of protons and neutrons = number of protons and neutrons (P + N) (P + N)

So,to get the # of neutrons we must Subtract So,to get the # of neutrons we must Subtract

Atomic # Atomic # from the from the Mass # Mass # = # Neutrons= # Neutrons

REVIEW TIMEREVIEW TIME

126 C

6 neutrons

PracticePracticeDetermine the # of protons,neutrons, & electronsDetermine the # of protons,neutrons, & electrons

ProtonsProtons NeutronsNeutrons ElectronsElectrons

HeHe

BB

MgMg

ZnZn

ProtonsProtons NeutronsNeutrons ElectronsElectrons

HeHe 22 22 22

BB

MgMg

ZnZn

ProtonsProtons NeutronsNeutrons ElectronsElectrons

HeHe

BB 55 66 55

MgMg

ZnZn

ProtonsProtons NeutronsNeutrons ElectronsElectrons

HeHe

BB

MgMg 1212 1212 1212

ZnZn

ProtonsProtons NeutronsNeutrons ElectronsElectrons

HeHe

BB

MgMg 1212 1212 1212

ZnZn 3030 3535 3030

Subatomic ParticlesSubatomic Particles

ElectronElectron: e: e--

negative chargenegative charge 9.11 x 109.11 x 10-31-31 kg kg

ProtonProton: p: p++

positive chargepositive charge 1.67 x 101.67 x 10-27-27 kg kg

NeutronNeutron: n: n00

no chargeno charge 1.67 x 101.67 x 10-27-27 kg kg

What did Battleship teach us?What did Battleship teach us?

Battleship simulated Rutherford’s Gold Foil Experiment.Battleship simulated Rutherford’s Gold Foil Experiment.

RutherfordRutherford BattleshipBattleship

Alpha ParticlesAlpha Particles Your missilesYour missiles

NucleusNucleus Pattern DrawnPattern Drawn

Atom is mostly empty Atom is mostly empty spacespace

All of the empty boxesAll of the empty boxes

Atoms vs IonsAtoms vs Ions

ATOMSATOMS IONSIONS

Protons = ElectronsProtons = Electrons Protons Protons ≠ Electrons≠ Electrons

CationsCations= More Protons= More Protons

Positive ChargePositive Charge

AnionsAnions= More Electrons= More Electrons

Negative ChargeNegative Charge

IONSIONS

cacattion (+)ion (+) anion (-)anion (-)

LiLi+1+1 ClCl-1-1

3 Protons3 Protons2 Electrons2 Electrons

17 Protons17 Protons

18 Electrons18 Electrons

Can’t Change the Number of Protons

IonsIons

An An ionion is an atom with a is an atom with a positive (+) or negative (-) positive (+) or negative (-) chargecharge

Atoms that gain electrons Atoms that gain electrons have - chargeshave - charges

Atoms that lose electrons Atoms that lose electrons have + chargeshave + charges

IsotopesIsotopesAtoms of an element can Atoms of an element can have different numbers of have different numbers of neutrons – these are neutrons – these are isotopesisotopes

The number of protons is The number of protons is always the same, but always the same, but since more neutrons add since more neutrons add more mass, the mass more mass, the mass number can be differentnumber can be different

IsotopesIsotopesProtons = ProtonsProtons = Protons

BUT……#Neutrons are DifferentBUT……#Neutrons are Different

SoSo

Mass # is DifferentMass # is Different

AtomAtom ProtonsProtons NeutronsNeutrons ElectronsElectrons Mass #Mass #

Carbon-12Carbon-12 66 66 66 1212

Carbon-13Carbon-13 66 77 66 1313

Carbon-14Carbon-14 66 88 66 1414

IsotopesIsotopes

Atoms are really smallAtoms are really small

How Big Is An Atom?

How Big Is An Atom?

The Scale of the UniverseThe Scale of the Universe

http://htwins.net/scale2/http://htwins.net/scale2/

Virtual AtomVirtual Atom

Ted Talk: How Small is an AtomTed Talk: How Small is an Atom

PracticePractice

• The atomic number of an atom is always The atomic number of an atom is always equal to the total number of:equal to the total number of:

a. Neutrons in the nucleusa. Neutrons in the nucleus

b. Protons in the nucleusb. Protons in the nucleus

c. Neutrons plus protons in the nucleusc. Neutrons plus protons in the nucleus

d. Protons plus electrons in the atomd. Protons plus electrons in the atom

PracticePractice

• If the number of electrons and protons are If the number of electrons and protons are not equal:not equal:

a. an atom existsa. an atom exists

b. an isotope existsb. an isotope exists

c. an ion existsc. an ion exists

d. None of the aboved. None of the above

PracticePractice

• An atom that has lost electrons has what An atom that has lost electrons has what type of charge?type of charge?

POSITIVEPOSITIVE

• Once it has lost electrons it is no longer Once it has lost electrons it is no longer an atom. What is it called?an atom. What is it called?

CATIONCATION

PracticePractice

• An atom of An atom of 4242Ca contains:Ca contains:

a. 20 protons and 22 neutronsa. 20 protons and 22 neutrons

b. 20 protons and 42 neutronsb. 20 protons and 42 neutrons

c. 20 electrons and 42 neutronsc. 20 electrons and 42 neutrons

d. 20 electrons and 22 protonsd. 20 electrons and 22 protons

PracticePractice

• Atoms that have the same atomic number Atoms that have the same atomic number but different mass numbers are called?but different mass numbers are called?

isotopesisotopes

PracticePractice• Look at the picture below and then fill in the Look at the picture below and then fill in the

chart:chart:

AtomAtom ProtonsProtons NeutronsNeutrons ElectronsElectrons Mass #Mass #

Lithium-6Lithium-6

Lithium-7Lithium-7

Lithium-8Lithium-8

33 33 33 66

33 44 33 77

33 55 33 88

PracticePractice

• The nucleus of an Fe-56 atom contains:The nucleus of an Fe-56 atom contains:

a. 26 protons, 30 neutrons and 26 electronsa. 26 protons, 30 neutrons and 26 electrons

b. 26 protons, 26 neutrons and 30 electronsb. 26 protons, 26 neutrons and 30 electrons

c. 26 protons and 56 neutronsc. 26 protons and 56 neutrons

d. 26 protons and 30 neutronsd. 26 protons and 30 neutrons

PracticePractice

• What did Rutherford’s Gold Foil experiment What did Rutherford’s Gold Foil experiment discover?discover?

a. electrona. electron

b. neutronb. neutron

c. nucleusc. nucleus

d. protond. proton

PracticePractice

• A A 5252CrCr3+ 3+ ion contains:ion contains:

a. 24 protons, 52 neutrons, 21 electronsa. 24 protons, 52 neutrons, 21 electrons

b. 24 protons, 28 neutrons, 24 electronsb. 24 protons, 28 neutrons, 24 electrons

c. 24 protons, 28 neutrons, 27 electronsc. 24 protons, 28 neutrons, 27 electrons

d. 24 protons, 28 neutrons, 21 electronsd. 24 protons, 28 neutrons, 21 electrons

PracticePractice

• What is the total number of electrons in What is the total number of electrons in an atom with an atomic number of 30 an atom with an atomic number of 30 and a mass number of 65?and a mass number of 65?

a. 30a. 30

b. 65b. 65

c. 35c. 35

d. 95d. 95

PracticePractice

• Who discovered the electron and how?Who discovered the electron and how?

a. Democritus, atomic theoriesa. Democritus, atomic theories

b. Dalton, cathode ray tubeb. Dalton, cathode ray tube

c. Rutherford, gold foil experimentc. Rutherford, gold foil experiment

d. Thomson, cathode ray tubed. Thomson, cathode ray tube