alchemy unit

Alchemy Unit

Investigation III: A Particulate WorldLesson 1: Pudding and Clouds Lesson 2: Building Atoms

Lesson 3: Subatomic HeavyweightsLesson 4: Life on the EdgeLesson 5: Shell GameLesson 6: Go FigureLesson 7: Technicolor Atoms

Alchemy Unit – Investigation III

Lesson 1:

Pudding and Clouds

Unit 1 • Investigation III

© 2004 Key Curriculum Press.

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.



• 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-InHere 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.


Lesson 5:

Shell Game



ChemCatalyst

The two drawings show two ways of representing the electron arrangement of the element calcium, Ca.

• Name at least two differences.

• Name at least two similarities.

1s2s

2pp

3sp3pp3d

4sp

4pp12

34



The Big Question

• How do electron subshells relate to the periodic table?




• Identify an element based on its electron configuration.



• Electron shells are divided into electron subshells.

Notes



Activity

Purpose: This lesson introduces you to electron subshells. You will explore how they are related to the periodic table.

(cont.)



1s2s

2pp

3sp3pp3d

4sp

4pp

(cont.)



Electron configuration Element

1s22s1

1s22s22p3 nitrogen, N

1s22s22p63s23p5

1s22s22p63s23p64s23d6

1s22s22p63s23p64s23d104p2

1s22s22p63s23p64s23d104p65s24d105p4 tellurium,Te

(cont.)



Making Sense

• How is the organization and structure of the periodic table related to electron subshells?

(cont.)



(cont.)



• An electron configuration is a list of all the subshells that have electrons for a given element. The number of electrons in a subshell is specified as a superscripted number.

Notes



Check-In

• Identify the element with the following electron configuration.

1s22s22p63s23p64s23d104p3



Wrap-Up

• Electron shells can be divided further into subshells, referred to as; s, p, d, f.

• Each subshell can hold a specific maximum number of electrons. The s subshell can hold 2 electrons, the p subshell can hold 6, the d subshell can hold 10 electrons, and the f subshell can hold 14.

(cont.)



• The periodic table can assist us in figuring out the sequence of filling the subshells with electrons.

• Chemists keep track of electrons and the subshells they are in by writing electron configurations.

(cont.)


Lesson 6:

Go Figure



ChemCatalyst

Consider the following electron configuration:

1s22s22p63s23p64s23d104p4

• What element do you think is represented by this electron configuration?

• How many valence electrons do you think this element has? Explain your reasoning.



The Big Question

• Where are the valence electrons in electron configurations?




• Write electron configurations and name valence electrons for an element.



Activity

Purpose: This activity teaches you a shorthand way to keep track of electron arrangements and how to identify valence electrons.

(cont.)



Element Electron configuration No. of valence

electrons

Identity of valence

electrons

1s22s22p3 5 2s22p3

1s22s22p63s23p1

1s22s22p63s23p64s23d2 2 or 4 4s23d2

1s22s22p4

Chlorine

1s22s22p63s23p64s23d104p65s1

Barium

(cont.)

(cont.)



Element Electron configuration No. of valence

electrons

Identity of valence

electrons

1s22s22p63s23p64s23d104p65s24d105p6

Silver 1 or 2 5s2

Potassium

Mercury 2 6s2

Terbium 2 6s2

Chromium 2,3,4,5,6 4s23d4

(cont.)

(cont.)



Element Electron configuration Valence electrons

Lithium, Li [He] 2s1 2s1

Potassium, K [Ar] 4s1 4s1

Scandium, Sc [Ar] 4s23d1 4s2 3d1

Zinc, Zn [Ar] 4s23d10 4s2

(cont.)



Making Sense

• If you know the electron configuration of an element, what other information can you figure out? List at least six things.

(cont.)



Check-In

• Write the electron configuration for bromine, Br.

• Write the noble gas electron configuration for Br.

• How many valence electrons does Br have? Explain.



Wrap-Up

• The noble gases can be used as placeholders in the periodic table when writing electron configurations.

• In the d-block or transition elements we find some exceptions to the rules when determining valence electrons.


Lesson 7:

Technicolor Atoms



ChemCatalyst

The ancient alchemists heated atoms to try to change them into gold. Knowledge of atomic structure assists us in figuring out what parts of an atom can be changed.

• Let’s say we started with a lithium atom and changed different parts of the atom. Look at the lithium atom below and four possible changes to it. What would we end up with in each case? (cont.)



The Big Question

• What part of the atom is changed by heating?




• Predict the color of the flame produced when heating a substance.



Activity

Purpose: In this activity you will observe evidence that atomic structure is changed when atoms are heated.

(cont.)



Safety Note:

• Tie back long hair.

• Keep long sleeves and clothing away from the flames.

(cont.)

(cont.)



Note: Do not exchange wires. For each solution, only use the wire that is already in that solution. After you use the wire, be sure to put it back in the solution from which it came.

(cont.)

(cont.)



Substance Name Color of Flame

sodium carbonate

potassium nitrate

copper nitrate

strontium nitrate

potassium chloride

sodium chloride

copper sulfate

strontium chloride

sodium nitrate

potassium sulfate

copper wire

copper penny



Making Sense

• The yellow color of the flame for sodium indicates that the sodium atoms changed in some way when they were heated. Consider the following possibility that the electron configuration of sodium changed from [Ne]3s1 to [Ne]4p1. What is the difference between [Ne]3s1 and [Ne]4p1? (Are the total number of electrons the same? Are the electrons in the same locations?) (cont.)



• Do you think gold can be made by changing the arrangement of electrons in atoms? Explain.

(cont.)



Blue/Greencopper nitratecopper sulfatecopper solidcopper penny

Redstrontium nitrate

strontium chloride

Yellow/Orangesodium carbonate

sodium chloride

sodium nitrate

Pink/Lilacpotassium nitrate

potassium chloride

potassium sulfate

Notes

(cont.)



Notes (cont.)



Check-In

• Predict the colors of the flames produced when heating the following substances. Explain your thinking.

Copper carbonate

Magnesium sulfate



Wrap-Up

• Electrons can move between subshells within an atom.

• An energy exchange occurs when electrons move farther away from the nucleus, or when they return to their original subshell.

• Moving electrons within an atom does not change the identity of the atom.

alchemy unit

Documents

key curriculum press

various models

carbon atom

small particles

notes cont

scientific evidence

bohr model

new evidence