hhs-chem-2010/11. chapter 4- page 86 “the structure of the atom” chemistry chemistry humble high...

HHS-CHEM-2010/11

Chapter 4- page 86“The Structure of the Atom”

ChemistryChemistryHumble High SchoolHumble High School

Ms . B Ms . B

Section 4.1 Early Theories of Matters

Read p- 88 from “ The greek philosophers Democritus…to…John Dalton”.

• Describe Which of Dalton’s beliefs about the atom are wrong? Explain why.

• Explain Why were alpha particles deflected in Rutherford’s gold foil experiment?

• Identify

HISTORY OF THE ATOMHISTORY OF THE ATOM

HISTORY OF THE ATOMHISTORY OF THE ATOM

460 BC Democritus develops the idea of atoms

he pounded up materials in his pestle and

mortar until he had reduced them to

smaller and smaller particles which he

calledATOMAATOMA

(greek for indivisible)

HISTORY OF THE ATOMHISTORY OF THE ATOM

1808 John Dalton

suggested that all matter was made up of

tiny spheres that were able to bounce

around with perfect elasticity and called

themATOMSATOMS

HISTORY OF THE ATOMHISTORY OF THE ATOM

1898 Joseph John Thompson

found that atoms could sometimes eject a

far smaller negative particle which he

called an

ELECTRONELECTRON

HISTORY OF THE ATOMHISTORY OF THE ATOM

Thompson develops the idea that an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron's charge

1904

like plums surrounded by pudding.

PLUM PUDDINGMODEL

Joseph John Thompson

HISTORY OF THE ATOMHISTORY OF THE ATOM

1910 Ernest Rutherford

He fired Helium nuclei at a piece of gold foil which was only a few atoms thick.

He found that although most of them passed through. About 1 in 10,000 hit and bounced back.

HISTORY OF THE ATOMHISTORY OF THE ATOM

gold foil

helium nuclei

He found that while most of the helium nuclei passed through the foil, a small number were deflected and, to his surprise, some helium nuclei bounced straight back.

HISTORY OF THE ATOMHISTORY OF THE ATOM

Rutherford’s new evidence allowed him to propose a more detailed model with a central nucleus.

He suggested that the positive charge was all in a central nucleus. With this holding the electrons in place by electrical attraction

However, this was not the end of the story.

Rutherford’s problem:In the following pictures, there is a target hidden by a cloud. To figure out the shape of the target, we shot some beams into the cloud and recorded where the beams came out. Can you figure out the shape of the target?

Target #1

Target #2

The Answers:

Target #1 Target #2

HISTORY OF THE ATOMHISTORY OF THE ATOM

1913 Niels Bohr

studied under Rutherford at the Victoria University in Manchester.

Bohr refined Rutherford's idea by adding that the electrons were in orbits. Rather like planets orbiting the sun. With each orbit only able to contain a set number of electrons.

Bohr’s Atom

electrons in orbits

nucleus

PLANETEREMODEL

I’m an electron!I’m a proton!I’m a neutron!

I was walking along and I saw these two.I was telling jokes to the neutron.The proton and I were having fun.

They looked so happy there together.I was p o s i t i v e l y charged!I couldn’t have amassed more happiness.

The proton looked happy, so I wandered closer.I could see the electron coming near.The who? Huh?

They were HUGE next to me!The electron was so tiny!! so cute!Like a speck of dust, or something…

I didn’t want to seem noisy, so I kept walking.Around and around the electron goes.Hey electron, you’re making the proton dizzy.

The proton seems so happy with the neutron.I’m having fun, but I still notice the electron.It won’t bother me if the electron hangs around.

I guess I’ll just wander around out here.I’m happy hanging out here.The center is cool, but sometimes it can be a “Bohring”.

Electrons circle around the nucleus of an atom.Protons are a main part of the nucleus of an atom.Neutrons also hang out in the nucleus of an atom.

Electrons have a negative charge. Protons have a positive charge. +Neutrons have no charge. 0

Electrons are little and have a mass of almost zero.Protons are big and have a mass of one.Neutrons are also big and have a mass of one.

What is an atom ?

• Definition : p- 90. Read Defining an atom.

Sec4.2 Subatomic Particles and the Nuclear Atom

• Nucleus :center of the atom and Home of Protons and Neutrons.*Proton = atomic number

• Has a positive (+) charge• Has a relative mass of 1• Determines the Element • Found inside the nucleus

What is the structure of an atom?

*Neutron• Has no (0) charge• Has a relative mass of 1• Determines the isotope

–Isotopes are two of the same element with different masses

• Found inside the nucleus

What is the structure of an atom?

• Electron– Has a negative (-) charge– Has a relative mass of 0 (zero)– Determines the ion– Found outside the nucleus

• Bohr model – electrons are in specific energy levels

• Electron cloud model – electrons are in a random cloud

HELIUM ATOM

+N

N

+-

-

proton

electron

neutron

Shell

What do these particles consist of?

ATOMIC STRUCTUREATOMIC STRUCTUREParticle Charge Mass (g) or

amuLocation

Electron (e-) -1

9.11 x 10-28

Or 0 amu Electron cloud

Proton (p+) +1

1.67 x 10-24

Or 1 amu Nucleus

Neutron (no) 0

1.67 x 10-24

Or 1 amu Nucleus

Sect.4.3 How Atoms Differ

Atomic number of an element is the number of protons in the nucleus of each atom of that element : it is what define an element

Element # of protons Atomic #

Carbon 6 6

Nitrogen 7 7

Oxygen 8 8

Mass number is the number of protons and neutrons in the nucleus of an isotope:

Mass # = p+ + n0

Nuclide p+ n0 Mass #

Oxygen - 10

- 8 8

- 31 15

8 1818

Oxygen 16 16

Phosphorus 3116

Sect.4.3 How Atoms Differ

What is a chemical symbol?

• Chemical symbol tells us what atom it is• Always a CAPITAL LETTER, sometimes

followed by a lower case letter• Ex: Oxygen O; Nitrogen N; Sodium Na• Copper Cu; Iron Fe• Cobalt Co; Carbon Monoxide CO• (Co is an element, CO is a compound)

ATOMIC STRUCTUREATOMIC STRUCTURE

the number of protons and neutrons in an atomHeHe44

22 Atomic number (subscript)

Atomic mass (superscript)

number of electrons = number of protonsHint: mass # is always › Atomic #

the number of protons in an atom

SymbolsSymbols BromineBromine

Find each of these: Find each of these: a)a) number of protons:number of protons:b)b) number of neutrons:number of neutrons:c)c) number of electrons:number of electrons:d)d) Atomic number:Atomic number:e)e) Mass Number:Mass Number:

Br

SymbolsSymbols

If an element has an atomic If an element has an atomic number of 34 and a mass number of 34 and a mass number of 78, what is the: number of 78, what is the: a)a) number of protons:number of protons:b)b) number of neutrons:number of neutrons:c)c) number of electrons:number of electrons:d)d) complete symbol:complete symbol:

SymbolsSymbols If an element has 91 If an element has 91

protons and 140 neutrons protons and 140 neutrons what is the what is the a)a) Atomic number:Atomic number:b)b) Mass number:Mass number:c)c) number of electrons:number of electrons:d)d) complete symbol:complete symbol:

SymbolsSymbols If an element has 78 If an element has 78

electrons and 117 neutrons electrons and 117 neutrons what is the what is the a)a) Atomic number:Atomic number:b)b) Mass number:Mass number:c)c) number of protons:number of protons:d)d) complete symbol:complete symbol:

Isotopes

• Dalton was wrong about all elements of the same type being identical

• Atoms of the same element can have different numbers of neutrons.

• Thus, different mass numbers.• These are called isotopes.

Naming Isotopes

• We can also put the mass number after the name of the element:carbon-12carbon-14uranium-235

Isotopes are atoms of the same element having different masses, due to varying numbers of neutrons.

Isotope Protons Electrons Neutrons NucleusHydrogen–1 (protium) 1 1 0

Hydrogen-2(deuterium) 1 1 1

Hydrogen-3(tritium)

1 1 2

IsotopesElements occur in nature as mixtures of isotopes.Isotopes are atoms of the same element that differ in the number of neutrons.

Calculating Atomic Mass

• Problem 4-3 page 103• Practice problems # 15-16 page 104

Atomic number equals the number of or .

Atomic mass equals the number of +

The Atomic Structure - Atomic Math Challenge

Atomic NumberSymbolNameAtomic Mass

protons electronsprotons neutrons

Assignment: Finish the rest of the worksheet and turn it in to your teacher.

The first energy street can hold only two Electron. The second energy street, called the Energy Freeway, can hold 8 electrons. The third energy street, called the Energy Superhighway, can hold 18 of them .

Nucleus ArcadeContains protons & neutrons

Energy Freeway Can hold 8 (2,6)

Energy Superhighway Can hold 18 electrons( 2,6,10)

Energy Street Can hold 2

electrons

ATOMIC STRUCTUREATOMIC STRUCTURE

There are two ways to represent the atomic

structure of an element or compound;

1. Electronic Configuration

2. Dot & Cross Diagrams

ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATION

With electronic configuration elements are represented numerically by the number of electrons in their shells and number of shells. For example: N

Nitrogen

7

14We know2e in 1st shell 5e in 2nd shell

2 + 5 = 7

So,Nitrogen configuration = 2 ,

5

ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATION

Write the electronic configuration for the following elements;

Ca

O

Cl Si

Na

40

20

23

11

16

35

8

17

28

14

B 5

11

a) b) c)

d) e) f)

2,8,8,2

2,8,1

2,8,7 2,8,4

2,32,6

DOT & CROSS DIAGRAMSDOT & CROSS DIAGRAMS

With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example;

Nitrogen N XX X

X

XX

X N 7

14

DOT & CROSS DIAGRAMSDOT & CROSS DIAGRAMS

Draw the Dot & Cross diagrams for the following elements;

O Cl8 17

16 35a) b)

O

XX

X

X

X

X

X

X

Cl

X

X

X

X X

XX

X

X

X

X

X

X

XX

X

X

X

SUMMARYSUMMARY1. The building block of Matters is Atom; Definition of an atom

2. The subatomic particles are: Proton, Neutron, Electron.

3. a) Protons are +ve and defines the Element.

b) Neutrons are neutral and defines the isotopes.

c) Electrons are –ve and defines the chemical properties of the element.

4. Isotopes are atoms of the same element that differ in the number of neutrons.

5. The Atomic Number of an atom = number of protons in the nucleus.6. The Atomic Mass of an atom = number of P + N in the nucleus.7. The number of Protons = Number of Electrons= overall charge = 08. Electrons orbit the nucleus in shells.9. Each shell can only carry a set number of electrons= 2,8,18

ATOMIC STRUCTUREATOMIC STRUCTURE

Electrons are arranged in Energy Levels

or Shells around the nucleus of an atom.

• first shell a maximum of 2 electrons

• second shell a maximum of 8 (2,6) electrons

• third shell a maximum of 18 (2,6,10)

electrons

Chapter 5 p-116Electrons in Atoms

• Read p-118