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Atoms pp.32-37

The Rutherford model of the atom (1911)

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Atoms Matter – Anything that has mass,

takes up space (volume) and has some sort of atomic structure.

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Atoms Atoms – are the smallest, simplest

fundamental units of matter.– The building blocks of matter.

Atoms are composed of 3 subatomic particles:– Protons, Neutrons, Electrons

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Atoms

Elements – are matter that is composed (made up of) only one type of atom.– A pure substance (like Au, Ag, Pt, Cu or

Al)– Your bling is NOT an element

Insert periodic table here

Periodic Table of the Elements

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PERIODIC TABLE P. 712 The periodic table is an organized listing

of all known types of elements.

H

Hydrogen

1

1.008

Name of element

Chemical symbol

Atomic Mass (weight)

AtomicNumber

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PERIODIC TABLE P. 712The first 92 elements are naturally occurring, meaning they are found on earth and are NOT man made. All the rest are made in a lab or nuclear reactor.

Ca

Calcium

20

40.078

Name of element

Chemical symbol

Atomic Mass (weight)

AtomicNumber

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Atomic Mass (Mass Number)

The atomic mass of an atom is equal to the sum of its protons and neutrons.– Atomic mass is also known as mass number or

atomic weight.

Mass is expressed in units called AMU’s (Atomic Mass Units)

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Atomic Number

The atomic number is equal to the number of protons in the atom’s nucleus.

– Remember the number of protons tells you which atom/element you have.

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ATOMIC mass minus the ATOMIC NUMBER equals the number of NEUTRONS in the nucleus

Atomic Mass - Atomic # = # NEUTRONS

HHydrogen

1 1.0079

What does the nucleus ofhydrogen have in it ?

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Periodic Table - Atomic Symbols

Information on an element is noted in different ways in different texts and periodic tables.

C

12

6

Mass Number

Atomic Number

6

C12.01

Atomic Number

Average atomic mass

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3 4 5 6 7

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Transition Metals = almost all have 2 valence e-

PERIODIC TABLE P. 712

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Periodic Table P. 712

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Periodic Table P. 712

Los Alamos National Lab Interactive Periodic Table

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Model of an atom

Atoms are too small to see even with a microscope. So we use models!– A cubic centimeter of air has 45 billion billion

atoms in it. That’s 45 with 18 zeros after it.– Another Example: Take a millimeter, divide into

1000 equal widths (called microns).– Now take one of those microns and divide it into

10,000 equal pieces. (one ten-millionth of a millimeter).

– That is how small an atom is!!!!!!

The Modern Model of the Atom

(Schroedinger 1926)

Dalton’s Model of the Atom (1803)

Rutherford Atomic Model (1911)

The Model of the Atom

(1904)Bohr Model of the Atom (1913)

Parts of the atom P. 35

ElectronsProtons

Neutrons

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Model of an atom

Atoms are mostly EMPTY space.

10-15 m

Neutron

Proton

Nucleus (protons and neutrons)

Space occupied by electrons

10-10 m

Model of an atom• Protons and neutrons are found INSIDE the

nucleus, and electrons are found as a cloud outside the nucleus.

10-15 m

Neutron

Proton

Nucleus (protons and neutrons)

Space occupied by electrons

10-10 m

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PROTONS

PROTONS – are subatomic particles found in the nucleus of the atom.

have a mass of 1.0 Atomic Mass Unit – let’s just call it 1.0 amu.

have a positive electrical charge of +1.

The number of protons determines the atom’s identity.

The nucleus is positively charged.

P

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NEUTRONS

NEUTRONS – are subatomic particles found inside the nucleus.

have a mass of slightly more than 1.0 amu.

Have an electrical charge of zero – thus they are neutral (hence the name).

The atomic mass of an atom is the number of protons + neutrons inside its nucleus.

If an atom has more or less neutrons than it normally should have, we call it an ISOTOPE.– Carbon-14 is an isotope of carbon, is radioactive and is used to date

fossils (like Mr, Mauer). More later.

N

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ELECTRONS

Subatomic particles found in electron shells or orbitals OUTSIDE the nucleus.

An electrons Mass is very tiny - let’s just call it zero (0).

Electrical charge is -1 (exactly opposite of the protons).

e

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ELECTRONS

Electrons determine the chemical properties of an atom. (how it reacts/behaves around other atoms).

Have potential energy.

The farther away from nucleus, the more energy they have.

Can change energy levels/shells/orbitals

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ELECTRONS

Atoms normally have a zero net charge overall.

That means the number of protons(+) in an atom equals the number of electrons(-).

Sometimes atoms may lose or gain electrons and become electrically charged atoms called IONS.

Subatomic Particles(parts of the atom)

Charge Mass Location

Proton (p+) +1 1.0073 amu

(about 1 amu)

nucleus

Neutron (n0) 0 1.0087 amu

(about 1 amu)

nucleus

Electron (e-) -1 0.00055 amu

(essentially 0 amu)

Outside nucleus

1 amu (atomic mass unit) is defined as 1/12 the mass of the carbon atom with 6 protons and 6 neutrons.

1 amu = 1.7 X 10-24 g (0.0000000000000000000000017 g)

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ISOTOPES

ISOTOPES are atoms of the same element which have different atomic weights because they have different numbers of neutrons.

For instance– Carbon normally has 6 protons, atomic mass of

12. (C-12)– Carbon can also have atomic mass of 13 (C-

13).– Carbon also exists with atomic mass of 14 (C-

14). Differences due to number of neutrons, not

protons

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Understanding Atoms

This diagram shows how to draw electrons for each energy level of an atom. A scientist named Neils Bohr created this representation.

1st energy level

2nd energy level

3rd energy level

4th energy level

Max. 2

Max. 8

Max. 18

Max. 32

•Atomic Mass•Atomic Number•All atoms are usually neutrally charged

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ELECTRON Energy Levels (Shells/Orbitals)

The first electron shell is full with 2 ELECTRONS

The second shell is full with 8 ELECTRONS

The third shell is full with 18 ELECTRONS.

The fourth shell is full with 32 ELECTRONS.

Electrons in the outermost shell are called VALENCE ELECTRONS.– These electrons are reactive and are involved in bonding to other

atoms (when the shell is not full!)

2, 8 , 18, 32, 32, 18, 8

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32

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ON THE TEST????

Be prepared to answer questions about the first 20 elements

Examples: atomic number, atomic mass, electron configurations, valance electrons, etc.

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WHY LEARN JUST THE FIRST 20?

Living things are composed of simple, common atoms...

NOT the big, rare fancy atoms ....

In fact about 95 percent of your body is composed of just 6 common atoms ....

CHNOPS - Remember these!

CARBON, HYDROGEN, NITROGEN, OXYGEN, PHOSPHORUS AND SULFUR

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WHAT DOES HYDROGEN LOOK LIKE ?

EPe-

+

Atomic Number = 1Atomic Mass Number = 1Electrical Charge = neutral

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HELIUM

HeHelium

2 4.0026

Can you draw this Bohr Model ?

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THE BOHR MODEL FOR HELIUM

PN

N

P

e-

e-

++

0

0

Atomic Number = 2Atomic Mass Number = 4Electrical Charge = neutral

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LITHIUM

LiLithium

3 6.941

39

THE LITHIUM MODEL

N43

THE FIRST SHELL IS FULL WITH TWO ELECTRONS

eP

e -

-

e-

+0

Atomic Number = 3Atomic Mass Number = 7Electrical Charge = neutral

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CARBON

CCarbon

6 12.011

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THE CARBON MODEL

N66 P

e-e-

e-

e-

e- e-+

0

Atomic Number = 6Atomic Mass Number = 12Electrical Charge = neutral

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SODIUM

NaSodium

11 22.989

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THE SODIUM MODEL

N1211

2

8

1 E

E

EP

Atomic Number = 11Atomic Mass Number = 23Electrical Charge = neutral

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POTASSIUM

KPotassium

19 39.102

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THE POTASSIUM MODEL

N2019

2

8

9E

E EP

Atomic Number = 19Atomic Mass Number = 39Electrical Charge = neutral