The Atom!Unit 4, Chapter 4

Click to see more pictures of the atom

And the UNITUNIT Essential Question is…

What is the structure of the

atom?

A.A. Democritus1.1. Greek Philosopher

2.2. First predicted the existence of the atom and gave the atom its name

3.3. “Atom” means “indivisible”

4.4. Stated that different atoms have different properties

5.5. He was laughed at and his theory was not accepted

460-370 B.C.

I.I. The development of the atomic model

Essential question: How was the atomic model developed?

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B.B. John Dalton John Dalton1.1. English Chemist

2.2. Through experimentation in 1803 he developed the first official

ATOMIC THEORY

3.3. His theory was accepted by the world and reads as follows…

Essential question: How was the atomic model developed?

1766-1844

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John Daltons’ 1803 Atomic TheoryJohn Daltons’ 1803 Atomic Theorya.a. Elements are composed of indivisible atoms

carbon- oxygen-

b.b. Atoms of the same element have the same mass

and atoms of different elements have different masses

c.c. Compounds contain atoms of more than one element

carbon dioxide-

d.d. Atoms of different elements always combine in the same way

carbon dioxide- carbon dioxide-

C O

C C CO

CO O

CO O CO O

C.C. J. J. Thomson1.1. Discovered negative

subatomic particles in 1897 and named them electrons

2.2. Stated that the atom is a ball of positive material in which electrons are scattered

Essential question: How was the atomic model developed?

Listen to JJ Thomson

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1856-1940

Real plum pudding

Known as the plum pudding model

See video

D.D. Ernest Rutherford1.1. Performed his famous gold

foil experiment in 1909

2.2. Discovered that the atom has a dense positive nucleus

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1871-1937

Essential question: How was the atomic model developed?

E.E. Niels Bohr1.1. In 1913 predicted that electrons move in fixed energy levels (orbits) around the nucleus

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1885-1962

Essential question: How was the atomic model developed?

2.2. Electrons can change orbits as they absorb or release energy

Essential question: How was the atomic model developed?

Here is how it works…

lowest energy

higher energy

highest energy

Energy passes through the atomAn electron absorbs some of that energy and moves to a higher energy level

Immediately, the electron will return to the ground state releasing that absorbed energy as light

This atom is in the ground state

repeat

F.F. Erwin Schrödinger1.1. Predicted the electron

cloud model in 1926

2.2. Energy levels are 3D areas not orbits

Essential question: How was the atomic model developed?

a.a. Based on complicated math

b.b. Shows electrons in an electron cloud (area of probability)

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1887-1961

II.II. The Structure of the Atom

Essential question: What are the parts of the atom?

1.1. Are located in the nucleus of the atom

A.A. Protons (p+)

2.2. Have a charge of +1

3.3. Have a mass of one atomic mass unit

(AMU)

4.4. Identify the element

Images from education.jlab.org

A proton is believed to be made of 3 quarks

Bonus info:

Essential question: What are the parts of the atom?

1.1. Are located in the electron cloud

B.B. Electrons (e-)

2.2. Have a charge of -1

Images from education.jlab.org

3.3. Have a mass of

1 1836 AMU

0.0005 amu

Essential question: What are the parts of the atom?

1.1. Are located in the nucleus of the atom

C.C. Neutrons (n)

2.2. Have no charge

Images from education.jlab.org

3.3. Have a mass of one AMU

A neutron is believed to be made of 3 quarks

Bonus info:

Here are some more facts about subatomic particles:

Essential question: What are the parts of the atom?

Bonus Info

Bonus Info

III.III. Gathering Information on an Element

Essential question: What are the number of subatomic particles in a given element?

Cl17

35.453

Chlorineatomic number

atomic mass

atomic number- the number of protons in the nucleus

atomic mass- average mass of the element as it occurs in nature (includes all isotopes)

A.A. Using the periodic table

mass number- the sum of the protons and neutrons in a given atom

Here are a few things to think about:

Where is most of the mass found inside the atom? The nucleus• Remember that an electron is 1836 times smaller than a proton

• The mass of the electrons in an atom is insignificant. The largest natural element is uranium which has 92 electrons. The total mass of 92 electrons is still only 5% of the mass of one proton.

• The mass of the electrons is miniscule compared to the mass of the nucleus

• The mass of an atom is basically equal to the mass of the nucleus which contains the protons and neutrons

•The mass of an atom is called the mass number

Essential question: What are the number of subatomic particles in a given element?

B.B. Processing the information

Cl17

35.453

Chlorine

Protons: The number of protons in an element is equal to the atomic number

Chlorine has 17 protons

Electrons: The number of electrons in a neutral atomneutral atom is equal to the number of protons

Chlorine has 17 electrons

Neutrons: The number of neutrons in an atom is equal to the mass number minus the atomic number

35 – 17 = 18 Chlorine has 18 neutrons

Essential question: What are the number of subatomic particles in a given element?

Lets practice!

Os76

190.23

Osmium

Protons: The number of protons in an element is equal to the atomic number

Osmium has 76 protons

Electrons: The number of electrons in a neutral atomneutral atom is equal to the number of protons

Osmium has 76 electrons

Neutrons: The number of neutrons in an atom is equal to the mass number minus atomic number

190 – 76 = 114 Osmium has 114 neutrons

Essential question: What are the number of subatomic particles in a given element?

91 – 40 = 51

Zr40

91.224

Zirconium

40

40

Protons:

Electrons:

Neutrons:

Essential question: What are the number of subatomic particles in a given element?

IV.IV. Isotopes of Atoms

Essential question: What are the different forms an atom can take?

A.A. All atoms of the same element have the same number of protons

B.B. The number of protons never change, they give the atom its identity

C.C. Isotopes are atoms of the same element that have a different number of neutrons

The Isotopes of Hydrogen

H1

1H

1

2H

1

3

protium deuterium tritium

p+ =

e- =

n =

mass =

p+ =

e- =

n =

mass =

p+ =

e- =

n =

mass =

1

1

0

1 amu

1 1

1 1

1 2

2 amu 3 amu

H1

1.0079

This is how hydrogen looks on the periodic table:

Which isotope is the most common hydrogen atom in the universe?

protium

Why? The atomic mass is closest to the mass of protium

Essential question: What are the different forms an atom can take?

Here is why…What is the average of the following numbers?

3

3

3

3

4

4+

20

20 6

= 3.3

Are there more 3’s or 4’s in the problem? 3’sIs the average closer to 3 or 4? 3

Lets practice!

V.V. Ions of Atoms

Essential question: What are the different forms an atom can take?

A.A. An ion is formed when electrons are lost or gained by an atom

B.B. An ion can be negative or positive

A negative ion has gained electrons

A positive ion has lost electrons

oxygen atom, O oxygen ion, O-2 calcium atom, Ca calcium ion, Ca+2

p+ = 8

e- = 8

p+ = 8

e- = 10

p+ = 20

e- = 20

p+ = 20

e- = 18

No net charge(neutral)

-2 charge No net charge(neutral)

+2 charge