Physical Science Chapter 4

Atomic Structure

Democritus and Aristotle◦ Democritus thought all matter consisted of

extremely tiny particles that could not be divided. (Cut aluminum foil in half)

◦ Also thought matter in liquids was round and smooth; in solids rough and prickly

◦ Aristotle thought there was no limit to the number of times matter could be divided.

4.1 Studying Atoms

Developed a theory to explain why the elements in a compound always behave in the same way.

Main Points◦ 1) All elements are composed of atoms.◦ 2) All atoms of the same element have the same

mass, and atoms of different elements have different masses.

◦ 3) Compounds contain atoms of more than one element.

◦ 4) In a compound, atoms of different elements always combine in the same way.

Dalton’s Atomic Theory

Used a cathode ray tube to show evidence for subatomic, charged particles.

Thomson’s Model

Plum pudding model (chocolate chip ice cream.

Negatively charged particles evenly spaced throughout a solid mass of positive charge.

Thomson continued

The Gold Foil Experiment – Evidence for a nucleus.

Rutherford’s Atomic Theory

Chapter 4Lesson 2

“Structure of the Atom”

A. An atom1. smallest part of matter2. Ripping paper example

B. Areas of an atom1. Nucleus – center of an atom

-holds protons and neutronsa. Protons (P) – positively charged

particle found in the nucleus.-has a mass of 1-has a charge of 1+

I. Subatomic Particles

b. Neutrons (N) – non-charged particle found in the nucleus.

-has a mass of 1-has no charge “0”

2. Electron Cloud – area around the nucleus which contains electrons

a. Electrons (e) – negatively charged particle found outside of the nucleus

-has a mass of 0-has a charge of 1--moves around the outside of the nucleus

Protons ElectronsNeutrons

Particle Mass Charge Location of particle

Particles in an Atom Review

Proton

Neutron

Electron

1

1

0

1+

0

1-

nucleus

nucleus

Electron cloud

A. Def – the # of protons in an atom’s nucleus. 1. Every carbon atom has 6 protons…2. Every neon atom has 10 protons…

B. On P.T. – located right above the chemical symbol

*Protons dictate the type of element we have**Electrons always equal the # of protons*

II. Atomic Number

A. Def – The sum of protons and neutrons in the nucleus of an atom.1. On P.T. – bottom number

-round up/down2. Ex: What is the mass number of the following elements?

Carbon OxygenIron CalciumSodium Zinc

III. Mass Number

12

56

23

16

40

65

3. Mass # = Protons + Neutrons

4. How many Neutrons on average are found in the following elements?Boron FluorineSilicon CopperSilver Gold118

14

6

61

10

35

A. Def – An atom that has a different number of neutrons.1. Does not affect the element2. Only changes the weight of the element

3. Ex: Boron-10 and Boron-11

IV. Isotope

p p p p p p p p p p

n n n n nn n n n n n

5 protons 5 protons

5 neutrons 6 neutrons

This meansthe mass #

Boron-10 Boron-11

4. How many neutrons do the following isotopes have?

Oxygen-14Titanium-50Magnesium-22Potassium-43Aluminum-23Iodine-130

6

28

10

24

10

77

A. Def – average mass of all isotopes of one element combined.1. Found on P.T. underneath chemical symbol.2. Ex: Carbon = 12.011

“Carbon has 3 known isotopes. Carbon-12, 13, and 14. Carbon-12 makes up

99% of all carbon on earth. Carbon-13 and 14 make up 1%.”

III. Average Atomic Mass

Chapter 4Lesson 3

“Modern Atomic Theory”

Chemistry Timeline…pg. 114-115

A. Def – a specific area where an electron is likely to be.

I. Bohr’s Model / Energy Levels

nucleus

2 electrons

8 electrons

18 electrons

32 electrons

e- e-

e-

e-

e-

e-

e-

e-

e-e-

e- e-e-

e-

e-

e-

e-

e-e-

e-

e-

e-e-e-

e-

e-

e-

e-

e-e-

e-

e- e-e-

e-

e-

e-

e-e-e-

e-e-

e-e-

e-e-e-e-

e-e-

e-e-

e-e-

e-

e-

e-e-

e-e-

Energy Level Maximum # of Electrons

1

2

3

4

2

8

18

32

Electrons in Energy Levels

1. Draw a picture of the following atoms with the correct number of e’s, p’s, and n’s…a. Na d. Heb. Al e. Cc. K f. S

2. Assign: Read pg. 118 and 1193. What is the difference between a ground

state and an excited state?

In Class Assignment