Alchemy Unit Investigation III: A Particulate World · 1/17/2012 · to 10 naturally occurring...

Alchemy Unit

Investigation III:

A Particulate World

Lesson 1: Pudding and Clouds

Lesson 2: Building Atoms

Lesson 3: Subatomic Heavyweights

Lesson 4: Life on the Edge

Alchemy Unit – Investigation III

Lesson 1:

Pudding and Clouds

© 2004 Key Curriculum Press.

Unit 1 • Investigation III

ChemCatalyst

In the 5th century BCE a Greek

philosopher named Leucippus and his

student, Democritis, stated, “All matter is

made up of particles that can be divided

called atoms.”

• What do you think atoms are?



The Big Question

• How have chemists thought about the

atom through history?



You will be able to:

• Describe some models of an atom and

explain how they differ.



• Atoms are extremely small particles,

which cannot be seen, even with

microscopes.

• All matter is made up of atoms.

• Scientists have created models to

describe atoms. Models are similar to

theories, but often include a picture or

physical representation.

Notes

(cont.)



• When a model is supported by

scientific evidence it is often

accepted by the scientific community.

• Scientific evidence is a collection of

observations that many people have

made. Everyone agrees on the same

collection of observations.

• As new evidence is gathered, models

are refined and changed.

(cont.)



Activity

Purpose: This lesson will introduce you to various models for the atom that have appeared over the past two hundred years. The descriptions of five models of the atom are on a separate handout.

(cont.)



Five Models of the Atom

(cont.)



Making Sense

• Examine the date of the atomic

evidence and then put the five models

in the correct order of their introduction

to the world of science.


Correct Order is…




• An atom is mostly empty space.

• The rest consists of a nucleus, which

is located in the very center of the

atom, and electrons, which are

located around the nucleus.

• The nucleus is very small (it would be

nothing more than a tiny speck in our

drawings, if we were to draw it to

scale).

Notes

(cont.)



• The nucleus is also very dense and

consists of two types of particles—

neutrons and protons.

• A neutron is a neutral particle with no

charge on it.

• A proton is a positively charged particle.

• Tightly bound together, neutrons and

protons make a positively charged

nucleus. (cont.)

Notes (cont.)



Notes (cont.)



Check-In

Here is a Bohr model of a carbon atom.

• List two things this model tells you

about atoms.

• List something this model does not tell

you about atoms.



Wrap-Up

• All matter is made up of extremely

small particles called atoms. These

particles are too small to be seen even

with a microscope.

• Science is theoretical and dynamic.

Models and theories are continually

being revised, refined, or replaced with

new models and theories.


Lesson 2:

Building Atoms



ChemCatalyst

A Bohr model of a helium atom and a

beryllium atom are given below.

Helium, He Berylium, Be

(cont.)



• List three similarities and three

differences.

• How do you think a gold atom is

different from a copper atom?

(cont.)



The Big Question

• What does the periodic table tells us

about the structures of different

atoms?




• Use the periodic table to identify the

properties of an elements atom.



• Atomic number is the number of

protons in the nucleus of an atom.

• Mass number is the mass of an

individual atom.

Notes



Activity

Purpose: This lesson will formally

introduce you to atomic structure.

Beryllium Atom Fluorine Atom Carbon Atom

(cont.)



element chemical symbol

atomic number

# of protons

# of electrons

# of neutrons

mass number

atomic weight

beryllium 5

fluorine 10

6 12

chlorine 18 35.45

lead 126

potassium 19 39

tin 70

tungsten 184 183.85

29 36

gold 118

(cont.)



Making Sense

• If you know the atomic number of an

element, what other information can

you figure out about the atoms of that

element?

• If you know the atomic number of an

element, can you figure out how many

neutrons an atom of that element has?

Can you come up with a close guess?

Explain.



• Mass number is the number of

protons plus the number of neutrons.

• Atomic mass is the “weight” or mass

of a single atom.

• Atomic weight is the decimal number

on the periodic table.

Notes



Check-In

Use your periodic table to identify the

following elements:

a) Atomic number 18

b) Has three electrons

c) Atomic mass of 16.0



Wrap-Up

• Each successive element has one

more proton than the element

preceding it.

• The atomic number is equal to the

number of protons.

(cont.)



• The number of electrons is equal to the

number of protons (as long as the

atom is neutral).

• The mass number is equal to the

number of protons plus the number of

neutrons (most of the mass is found in

the nucleus).

(cont.)


Lesson 3:

Subatomic Heavyweights



ChemCatalyst

A chemist investigating a sample of

lithium found that some atoms have a

lower mass than other atoms. The

chemist determined that the structures of

the two types of atoms would be similar

to the two drawings below.

(cont.)



• What is different about the two atoms?

• What is the atomic number of each atom?

• What is the mass number of each atom?

• Do you think they are both lithium atoms?

Why or why not?

(cont.)



The Big Question

• How do isotopes of an atom account

for the atomic weight of an element?




• Predict the isotopes of an element.



• Atoms of the same element that have

different numbers of neutrons are

called isotopes.

• Atomic mass units (amu) are

“invented” measurement units of the

atomic mass.

Notes



Activity

Purpose: In this lesson you will

investigate isotopes and how they affect

atomic weight.

(cont.)



boron atom 1 2 3 4 5 6 7 8 9 10

# protons

# neutrons

# electrons

(cont.)

(cont.)



Element Chemical

Symbol

Atomic

Number

Atomic

Weight

# of

protons

# of

electrons

# of

neutrons

Boron B 5 or 6

Chlorine 17

Lithium 6.94

Vanadium V 23

Nitrogen 7

Magnesium

Argon Ar 39.9 18. 20.

or 22

(cont.)



Making Sense

• Explain why the atomic weights listed

in the periodic table are not usually

whole numbers.



• While the element iron is defined as

being made up of neutral atoms with

26 protons and 26 electrons, not every

iron atom has the same number of

neutrons.

• Atoms that have the same number of

protons but different numbers of

neutrons are called isotopes.

Notes

(cont.)



• What we call the atomic weight on the

periodic table is actually the average

atomic mass of that element’s naturally

occurring isotopes.

• Isotopes have similar chemical

properties in that they combine with

other elements to form similar

compounds.

Notes (cont.)

(cont.)



• Atomic Weight is the weighted

average of the atomic masses of

different isotopes taking into account

their abundance.

(cont.)

(cont.)



(cont.)



Check-In

• Predict the isotopes of carbon, C.

Which isotope is more abundant? How

do you know?



Wrap-Up

• Elements may have anywhere from 2

to 10 naturally occurring isotopes.

• The atomic weight of an element listed

on the periodic table is actually the

average mass of the naturally

occurring isotopes of that element.

• Isotopes have the same number of

protons and electrons, but different

numbers of neutrons. (cont.)



• Isotopes of a single element exhibit

similar properties in that they form

similar compounds.

• Isotopes are referred to by their mass

numbers.

(cont.)


Lesson 4:

Life on the Edge



ChemCatalyst

The three atoms below have similar

reactivity and chemical behavior.

• Where are these elements located on

the periodic table?

• What do you think might be responsible

for their similar properties?

(cont.)



(cont.)



The Big Question

• What accounts for the similar

chemistry of elements in the same

group?




• Give the number of valence electrons

for an element.



Activity

Purpose: The various physical and

chemical properties of the elements can

be traced to the electrons. By studying

electrons further we may be able to

unlock the key to creating substances

similar to gold. This lesson will reveal the

arrangement of electrons within atoms.



Making Sense

• Explain how you can determine the

arrangement of an element’s electrons,

from the element’s position on the

periodic table.



• Bohr proposed that electrons could be

found in different shells around the

nucleus.

• The letter “n” is referred to as the

quantum number.

Notes



(cont.)

(cont.)



• The outermost shell of each drawing is

called the valence shell.

• The valence shell contains the

valence electrons.

• All other electrons are considered core

electrons.

(cont.)



Check-In

Provide the following information for

element number 34.

a) The element’s name and symbol.

b) The number of protons in the nucleus.

c) The total number of electrons for this

element.

d) The number of core electrons for this

element. (cont.)



e) The number of valence electrons.

f) The group number for this element.

g) The names of other elements with

similar chemistry.

(cont.)



Wrap-Up

• Electrons occupy different shells

around the nucleus of an atom.

• Each electron shell can hold a specific

maximum number of electrons.

• The valence electrons are in the

outermost electron shell of an atom.

Electrons that are not valence

electrons are called core electrons.

(cont.)



• Elements with the same number of

valence electrons have similar

chemistry and are in the same group.

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Alchemy Unit Investigation III: A Particulate World · 1/17/2012 · to 10 naturally occurring...

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