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Chapter 3 - Atoms the building blocks of matter

- Taken from Modern Chemistry written by Davis,

Metcalfe, Williams Castka

Section 3.1 The Atom from philosophical idea

to scientific theory

- Objectives

HW Notes on section 3.1 pgs 65-67

- Students will be able to
- Explain the laws of
- Conservation of mass
- Definite proportion
- Multiple proportion
- Summarize the 5 essential points of Daltons

atomic theory - Explain the relationship between the 5 essential

points and the above mentioned laws

Section 3.1 The Atom from philosophical idea

to scientific theory

- Foundations of Atomic Theory

As early as 400 B.C.E. particle theory of matter

was supported the particle was called an atom

based on the Greek for indivisible. Supported

by Democritus Aristotle did not believe this

theory and his opinion lasted for 2 000 years.

Felt all matter was continuous.

Section 3.1 The Atom from philosophical idea

to scientific theory

- Foundations of Atomic Theory (continued)

By 1700s accepted idea that an element could not

be broken down further. Back

The transformation of substance or substances

into one or more new substances was known as a

chemical reaction.

By the 1790s there was a new emphasis on

quantitative analysis of chemical reactions

Section 3.1 The Atom from philosophical idea

to scientific theory

- Foundations of Atomic Theory (continued)

This work lead to the discovery of several laws.

. .

Law of Conservation of matter which states that

mass is neither destroyed or created during

ordinary chemical or physical reactions.

Back

Section 3.1 The Atom from philosophical idea

to scientific theory

- Foundations of Atomic Theory (continued)

The law of definite proportions, sometimes called

Proust's Law, states that a chemical compound

always contains exactly the same proportion of

elements by mass.

Book example salt is always 39.34 Na (sodium)

and 60.66 Cl (Chlorine) by mass

Section 3.1 The Atom from philosophical idea

to scientific theory

- Foundations of Atomic Theory (continued)

The law of multiple proportions, statement that

when two elements combine with each other to form

more than one compound, the weights of one

element that combine with a fixed weight of the

other are in a ratio of small whole numbers.

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Section 3.1 The Atom from philosophical idea

to scientific theory

- Daltons Atomic Theory

1.All matter is made of extremely small particles

called atoms. Relationship

2.All atoms of the same element are identical in

size, mass other properties. Relationship

3.Atoms cannot be subdivided, created or

destroyed. Relationship

4.Atoms of different elements combine in

WHOLE-number ratios to form compounds.

5.In chemical reactions atoms are combined,

separated or rearranged. Relationship

Section 3.1 The Atom from philosophical idea

to scientific theory

- Modern Atomic Theory

Dalton turned ideas (of ancient Greeks) into

scientific theory

Today we know that atoms can be divided, but the

law of conservation of matter holds true still.

Section 3.1 The Atom from philosophical idea

to scientific theory

- Quiz Break

Section 3.2 The Structure of the Atom

- Objectives

HW Notes on section 3.2 pgs 70-74

- Students will be able to
- Summarize the observed properties of cathode

rays that led to the discovery of the electron. - Summarize the experiment carried out by

Rutherford and his co-workers that led to the

discovery of the nucleus. - List the properties of protons, neutron and

electrons - Define atom.

Section 3.2 The Structure of the Atom

- Discovery of the Electron

1st discovery of a subatomic particle resulted

from investigations into the relationship between

electricity and matter.

Section 3.2 The Structure of the Atom

- Discovery of the Electron - Cathode Rays and

Electrons

Hypothesized that the glow was caused by a stream

of particles which they called a cathode ray.

- Tested and found that
- An object placed between the cathode ray and the

opposite end casts a shadow. - A paddle wheel placed on rails rolled toward the

anode from the cathode.

Dont forget hyperlink

Section 3.2 The Structure of the Atom

- Discovery of the Electron - Cathode Rays and

Electrons (continued)

This supported the idea of a cathode ray. . .

- Further testing found that
- Cathode rays were deflected by a magnetic field.
- Deflected away from negatively charged objects.

Thompson hypothesized that the ray was a

particle, a negative one later named electrons.

Section 3.2 The Structure of the Atom

- Charge and Mass of the electrons

Thompsons work showed that the electron has a

very large charge for its tiny mass

R. A. Millikan (right) showed the mass to be

9.109 x 10-31 kg

Section 3.2 The Structure of the Atom

- Charge and Mass of the electrons (continued)

Based on that information two more inferences

were made about atomic structure.

- Atoms are electrically neutral so there must be

positively charged particles to balance out the

negative electron. - Because electrons have so much less mass than

atoms, atoms must contain other particles which

account for most of their mass.

Section 3.2 The Structure of the Atom

- Discovery of the Atomic Nucleus

Ernest Rutherford associates bombarded a thin

gold foil with alpha particles ( charge 4 x

mass of H atom) Expected most particles to pass

through with slight deflection shocked to find

that 1 in 8 000 were redirected back toward

source.

Section 3.2 The Structure of the Atom

- Discovery of the Atomic Nucleus (continued)

Rutherford reasoned that the bounce back was from

a densely packed bundle with a positively bundle

he called the nucleus.

If the nucleus were the size of a marble the atom

would be the size of a football field

Section 3.2 The Structure of the Atom

- Composition of the Atomic Nucleus

Except for the simplest type of hydrogen all

atomic nuclei are made of two types of particles,

protons and neutrons.

Protons have a () charge which balances out the

charge of the electrons. Mass 1.673 x 10-27 kg

Neutrons have a no charge and a mass 1.675 x

10-27 kg

Section 3.2 The Structure of the Atom

- Composition of the Atomic Nucleus (continued)

Nuclei of atoms of different elements differ in

the of protons they contain and therefore in

the amount of positive charge.

Section 3.2 The Structure of the Atom

- Properties Summarized

Particle Symbols Relative electric charge Mass number Relative Mass (amu) Actual mass (kg)

Electron e-, -1 0 0.000 5486 9.109 x 10-31

Proton p, 1 1 1.007 276 1.673 x 10-27

Neutron no, 0 1 1.008 665 1.675 x 10-27

1 amu (atomic mass unit) 1.660 540 x 10-27 kg

Section 3.2 The Structure of the Atom

- Composition of the Atomic Nucleus - Forces in the

Nucleus

Like forces generally repel one another however

when two protons are extremely close there is a

strong attractions

These short-range proton-neutron, proton-proton,

and neutron-neutron forces hold the particles

together and a referred to as nuclear forces.

Section 3.2 The Structure of the Atom

- The sizes of Atoms

Atomic radii range from 40 to 270 pm

(picometers) Where as the nuclei of atoms have a

much smaller radii About 0.001 pm

Section 3.3(A) Counting Atoms

- Objectives

HW Notes on section 3.3 pgs 75-80

- Students will be able to
- Explain what isotopes are.
- Define atomic number and mass number, and

describe how they apply to isotopes. - Given the identity nuclide, determine its number

of protons, neutrons and electrons.

Section 3.3(A) Counting Atoms

- Atomic Number

The atomic number of an element is the number of

protons in the nucleus of each atom of that

element

Section 3.3(A) Counting Atoms

- Isotopes

Isotopes are atoms of the same element that have

different masses. All hydrogen contain the

same number of protons but may contain different

number of neutrons.

Section 3.3(A) Counting Atoms

- Mass Number

The mass number is the total number of protons

and neutrons in the nucleus of an isotope.

Mass Number 1 2 3

Section 3.3(A) Counting Atoms

- Isotopes - pogil

Isotopes Are all atoms of an element alike?

Section 3.3(A) Counting Atoms

- Isotopes Pennium Lab

Isotopes of Pennium

Section 3.3(A) Counting Atoms

- Designating Isotopes

Nuclide is a general term for any isotope of any

element.

S elements symbol

Nuclear Symbol

a protons neutrons

b protons

Protons ______ Neutrons _______ Electrons

________

Bromine has

Practice

Practice Key

Section 3.3(A) Counting Atoms

- Relative Atomic Masses

The standard used by scientist to govern units of

atomic mass is the carbon-12 nuclide. One atomic

mass unit , or amu is exactly 1/12th the mass of

a carbon-12 atom, or 1.660 540 x 10-27 kg

Although isotopes may have different masses,

they do not differ significantly in their

chemical behavior.

Section 3.3(A) Counting Atoms

- Average Atomic Masses of Elements

Average atomic mass is the weighted average of

the atomic masses of the naturally occurring

elements.

Example with marbles (100 total) 25 marbles x

2.00 g 50 g 75 marbles x 3.00 g 225 g Adding

the masses gives 50 g 225 g 275 g Divide

this by the total number of marbles and you get

an average marble mass of 2.75 g

Section 3.3(A) Counting Atoms

- Average Atomic Masses of Elements (continued)

Average atomic mass How are the masses on the

periodic table determined?

(KEY)

Section 3.3(B) Counting Atoms

- Objectives

HW Notes on section 3.3 pgs 80-85

- Students will be able to
- Define mole in terms of Avogadros number, and

define molar mass. - Solve problems involving mass in grams, amount in

moles and number of atoms of an element.

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms - the Mole

A mole (abbreviated mol)is the amount of a

substance that contains as many particles as

there are atoms in exactly 12 g of carbon-12.

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms Avogadros

number

The number of particles in a mole has been

experimentally determined in a number of

ways. Avogadros number 6.011 1367 x 1023 is

the number of particles in exactly one mole of a

pure substance. For ours (and most purposes)

Avogadros number is rounded to 6.022 x 1023

It is a big number!

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms Molar Mass

The alternative definition of mole is the amount

of substance that contains avogadros number of

particles. The mass of one mole of a pure

substance is called the molar mass of that

substance. Usually written in units of g/mol.

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms Gram/Mole

Conversions

There are 3 mole equalities. They are 1 mol

6.02 x 1023 particles 1 mol g-formula-mass

(periodic table) 1 mol 22.4 L for a gas at STP

STP 0 C 1 atm Pressure

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms Conversions

There are 3 mole equalities. They are 1 mol

6.02 x 1023 particles 1 mol g-formula-mass

(periodic table) 1 mol 22.4 L for a gas at STP

These become. . .

Reference Sheet

There are 3 mole equalities. They are 1 mol

6.02 x 1023 particles 1 mol g-formula-mass

(periodic table) 1 mol 22.4 L for a gas at STP

These become. . .

Section 3.3(A) Counting Atoms

- Relating Mass to Numbers of Atoms What does it

mean?

g-formula-mass (periodic table)

For a single element it is simply the atomic mass

found on the periodic chart

Section 3.3(A) Counting Atoms

- Relating Mass to Numbers of Atoms Examples

g-formula-mass (periodic table)

N

Ca

Ag

Ba

Section 3.3(A) Counting Atoms

- Relating Mass to Numbers of Atoms What does it

mean?

g-formula-mass (periodic table)

For a COMPOUND you will need to calculate using

atomic mass found on the periodic chart

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms EXAMPLE

g-formula-mass (periodic table)

COMPOUNDS

Table Salt NaCl

Water H2O

Sugar (glucose) C6H12O6

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms EXAMPLE

g-formula-mass (periodic table)

COMPOUNDS

inorganic salt (soil fertilizer) (NH4)2SO4

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms MOLE

PRACTICES

Practice 1

Practice 2

Practice 2 (Key)

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms FUN WITH

MOLES

Given 2.860 m ? ceiling height 9.630 m ?

room depth 10.620 m ? room width

Atmosphere composition Nitrogen -

78.084 Oxygen - 20.95

1 000 L 1 m3

How many mols of O2 and N2 are present in this

room?

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms FUN WITH

MOLES

Average lung volumes in healthy adults7 Average lung volumes in healthy adults7 Average lung volumes in healthy adults7

Volume Value (litres) Value (litres)

Volume In men In women

Inspiratory reserve volume 3.3 1.9

Tidal volume 0.5 0.5

Expiratory reserve volume 1.0 0.7

Residual volume 1.2 1.1

Atmosphere composition Nitrogen -

78.084 Oxygen - 20.95

How many particles of O2 and N2 are taken in with

each breath?

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms suggestions

- Relax
- Look for things you recognize
- Estimate size of final answer (with this comes

do I remember using any of these before) - Set up and work out
- Double check with estimate and your sig figs

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms MORE MOLE

PRACTICES

Practice 3

Practice 3 (KEY)

TAKE-HOME QUIZ (KEY)

TAKE-HOME QUIZ

Practice 4

Practice 4 (KEY)

Section 3.3(B) Counting Atoms

- Relating Mass to Numbers of Atoms Q - 4

Want to get to Mols...

100 atoms Ar

? 1 x 102 atoms Ar

1 x 102 atoms Ar

1 mol

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

X -------------------------

1

6.02 x 1023 particles

0.166 x 10-21 particles , which is equal to 1.66

x 10-1 x 10-21

Or more properly written as 1.66 x 10-22 mols Ar