CHAPTER 4: THE ATOM PHYSICAL SCIENCE

By C. Goodman, Doral Academy Preparatory High School, 2011-2013 Based on a PowerPoint presentation by Mrs. S. Temple, Doral Academy Preparatory High School

Essential Question Section 4.1 The Atomic Model

What is the atomic model according to Rutherford, and how was it developed? (Explain the contributions of Democritus, Dalton, Rutherford and Thomson.)

Section 4.1 Vocabulary

• Democritus

• Atom

• Dalton

• Thomson

• Electron

• Rutherford

• Nucleus

Democritus – atomic idea

Democritus coined the term “atom”

atomos = Greek word “indivisible”

All substances are formed

of atoms.

Atoms are the smallest

particles of matter

John Dalton

(1766-1844)

English born

Introduced his Atomic Theory

in 1808

Based theories on

Democritus’ work

Dalton used experimental evidence.

Dalton’s Atomic Theory 〉What did Dalton add

to the atomic theory?

〉According to Dalton, all atoms of a given element were exactly alike, and atoms of different elements could join to form compounds.

Thomson – the electron

• Thomson: discovered the electron

• Cathode ray tube experiment 〉He concluded that… 〉 all atoms have sub-atomic particles called electrons. 〉The electrons are much smaller than the other parts of the

atom 〉They are negatively charged.

Rutherford – the Nucleus Gold foil experiment

• Rutherford proposed that most of the mass of the atom was concentrated at the atom’s center

He was right.

• Rutherford conducted the gold-foil experiment.

• Rutherford discovered the nucleus.

• nucleus: an atom’s central

region, which is made up of

protons and neutrons

Flowchart: atomic theory

Democritus Atoms Can’t be divided

Dalton: Compounds Combinations of elements

Thomson: Electron

Also inferred proton

Rutherford : Nucleus Inferred that the electrons orbit the nucleus

Essential Question Section 4.2 The structure of atoms

1. Compare and contrast the parts of the atom.

2. How are atoms and isotopes related?

3. What is a mole, and how is it related to average atomic mass?

4. Given an amount of a substance, how can one convert between the number of grams in the substance and number of moles, and vice versa?

Section 4.2 Vocabulary

•Proton

•Neutron

•Atomic number

•Mass number

•Isotope

•Unified atomic mass unit (AMU)

•Mole

•Molar mass

How small is small?

The Building Blocks of Matter

Prions

Quarks (6 Flavors)

Protons Neutrons Electrons

Atoms/ Elements

Compounds

Atomic Number (Z) # of protons of each atom of that

element

Placed in increasing order on the Periodic Table

This # IDENTIFIES the element

How?

Look on the periodic table!

Particles Symbol

Charge Location Mass (amu)

Protons p+ Positive charge

Nucleus 1

Neutrons n0 Neutral (no) charge

Nucleus 1

Electrons e- Negative charge

In area surrounding nucleus

--

Nucleus and Electron Cloud Nucleus

Positive charge because protons are positive and neutrons have

no charge (neutral)

Makes up most of atom’s mass

Electron cloud

Region of space around nucleus; negative charge because of

electrons

Make up most of atom’s volume

Mass Number (A) Total number of protons and neutrons

Helps identify isotopes

Mass #

- Atomic #

----------------

# of Neutrons

Isotopes

Atoms of the same element that

have different masses

The Isotopes of an element have

Same chemical properties

Same atomic #’s and # p+

Different mass #s

Different # no

Calculating the number of neutrons

Hyphen-notation Nuclear Notation Atomic mass Atomic # # Neutrons

Example.

Carbon-11 611C 11 6 5

Mass #

- Atomic #

----------------

# of Neutrons

Calculating the number of neutrons

Hyphen-notation Nuclear Notation Atomic mass Atomic # # Neutrons

Example.

Carbon-11 611C 11 6 5

Mass #

- Atomic #

----------------

# of Neutrons

Classwork - Isotopes

Hyphen-notation Nuclear Notation Atomic mass Atomic # # Neutrons

1. Oxygen-15

2. Silicon-30

3. Phosphorus-30

4. Nitrogen-30

5. Neon-22

6. Sodium-22

And now it’s time for….. Mole calculations!!!

Don’t be

afraid…yet.

The Mole

The mole is the SI unit

for a large amount of something.

1. We have other units for amount…

e.g. pair, dozen, baker’s dozen, etc.

2. How many items are in a mole?

Introducing… Avogadro’s number

3. 6.022 × 1023 atoms per mol

4. This number is so large it is pretty much

only used for counting atoms and

molecules

e.g. 1 mol H2O has 6.022 × 1023 atom, i.e.

602,200,000,000,000,000,000,000 atoms

Be

honest:

Does this

lab coat

make me

look fat?

Each element has a unique “molar mass”

• Molar mass =

mass of one mole of an

element or compound.

• Units of measure: g/mol

• To find the molar mass of

an element, look at its

average atomic mass in

the Periodic Table.

• Average atomic mass of

Li = 6.941 amu (per atom)

• Molar mass of lithium =

6.941 g/mol (of atoms)

This means that

one atom of Li

weighs 6.941 amu

And 6.022 x 1023

atoms of

Li weigh 6.941 g!

1. Moles to Grams

Equation

#moles (mol) x molar mass (g/mol)

1. Moles to Grams - Example

What is the mass in grams of 3.50 mol Cu?

grams Cumoles Cu × = grams Cu

moles Cu

63.55 g Cu3.50 mol Cu × =

1 222

mol Cu g Cu

Moles to Grams: Practice Problems Book: p. 126

Practice problems on the bottom of the page, #1a-d

1. Write questions and answers

2. Show work

3. Write neatly; it’s for a classwork grade!

2. Grams to Moles

Equation

aka

Equation

Mass (g) ÷ molar mass (g/mol)

2. Grams to Moles •Sample Problem C

•A chemist produced 11.9 g of aluminum, Al. How many moles of aluminum were produced?

moles Al

grams Al = moles Algrams Al

1 mol Al11.9 g Al =

26.0.441

98 g Al mol Al

Grams to Moles: Practice Problems Add the following questions to your paper on moles to grams…

How many moles are in…

e. 650 g of Nitrogen

f. 38 grams of Sulfur

g. 12 grams of Carbon

h. 890 g Oxygen

1. Write questions and answers

2. Show work

3. Write neatly; it’s for a classwork grade!

Essential Questions - Section 4.3 Modern Atomic Theory

1. What is the modern model of the atom?

2. How does the modern atomic model differ from Rutherford’s model of the atom?

3. How are the energy levels of an atom filled?

Section 4.3 Vocabulary

•Energy level

•Orbital

•S-orbital

•P-orbital

Modern Model of the Atom 1. Think as an atom as surrounded by concentric sphere.

Each sphere is called an “energy level”.

Modern Model of the Atom

2. Electrons can be found only in certain energy levels, not between levels.

Modern Model of the Atom

3. Location of electrons cannot be predicted precisely (they are not in orbits, they are in clouds, which are called “orbitals”).

Modern Model of the Atom

4. Electrons must gain energy to move to a higher energy level or lose energy to move to a lower energy level.

How do electrons gain energy? By getting zapped with light, electricity, heat, or any other kind of energy.

How many electrons does an element have? As many as the number of protons.

…which is the same as the atomic number. So if the atomic number is 4, then you have 4 protons and 4 electrons But you don’t know how many neutrons you have!

Energy Levels

1. An area around the nucleus where electrons are located.

2. Each energy level may contain only a certain number of electrons.

How are the energy levels of an atom filled?

1. Depends on the number of electrons 2. Filled “bottom up”