CHEMISTRY CATALYSTSFall 2011 – Week 6 (Atomic Structure & Nuclear)

Catalyst (5 min) 9/17/12 Atomic Models EQ: How can I model the parts of an

atom?1. Calculate the numbers of protons,

neutrons, and electrons in these three isotopes.Helium – 4 Neon - 21

2. Draw Bohr models of these three isotopes.

Review

Question 1

1. How many protons, neutrons, and electrons does Neon have?

Question 2

Draw a Bohr model of an oxygen atom?

Question 3

Who discovered electrons?

Question 4

How many protons, neutrons, and electrons does Oxygen-15 have?

Catalyst (5 min) 9/14/11 Nuclear Decay EQ: How does the nucleus of an atom

change during decay?

What do you think when you hear the word nuclear?

Is it a positive word or a negative word?

Write 4-6 detailed sentences describing your reaction.

NUCLEAR DECAY

When it all just falls apart…

What is Nuclear Decay?

Nuclear decay occurs when the nucleus of an atom is unstable.

Particles and/or energy are emitted (given off) from the nucleus to help stabilize it.

Nuclear Foldable (Front)

alpha

beta

gamma

Nuclear Foldable (Inside)

Composition:Charge:Mass:Penetration:Shielding:Symbols:

Alpha Particles ()

Made of 2 protons & 2 neutrons

Charge = +2 Mass = 4 amu (Heavy and slow particles) Low penetrating power Can be blocked by a single

sheet of paper Symbols used:

He

42

42

Alpha Decay

Alpha decay occurs when a large nucleus ejects two protons and two neutrons (an alpha particle).

The results are a mass change of 4 amu and a more stable nucleus.

Beta Particles ()

Made of 1 electron Charge = -1 Mass = 1/1840 amu (Fast and light particles) Medium penetrating power Can be blocked by thin metal

like aluminum foil or thin wood

Symbols used: e

0101

Beta Decay

Beta decay occurs when a neutron splits into a proton and an electron.

This results in no change in mass, but the isotope does become a different element.

Gamma Rays ()

Made of waves, not particles

Charge = 0 Mass = 0 High penetrating power Can be mostly blocked by

using 10cm or more of solid lead, but never completely

Symbol used: 00

Gamma Ray Radiation

Gamma radiation is produced by a nucleus in the “excited state.” When a nucleus has too much energy, it can release some of it as gamma radiation.

The result of this is no change in mass, charge, or composition – just a more stable nucleus with less energy.

1

2

3

1

2

3

1 1

2 2

3 3

Determining Charge of Radiation

Shielding Radiation

Alpha ()

shielding

Beta ()

shielding

Gamma ()

shielding

Warm Up 9/15/11 Nuclear Decay EQ: What is the half-life of a radioactive

isotope?You have three radioactive cookies:

One emits particles. One emits particles. One emits particles.

You must eat one, hold one in your hand, & hold one in your pocket.

Which cookie goes where? Explain.

Nuclear Cookies

Math Equations

4 + ___ = 12

10 = ___ + 4

12 + 9 = ___ + -1

8

6

22

Chemistry Equations

Math uses an = sign.Chemistry uses an .

Example: H2 + O2 H2O

reads “Hydrogen plus oxygen yields water.”

- decay

U Th + He23892

23490

42

Add this equation to your foldable.

Note that the left side and right side are equal for the top number and bottom numbers.

- decay

C N + e146

147

01

Add this equation to your foldable.

Note that the left side and right side are equal for the top number and bottom numbers.

- decay

Al Al + 2713

2713

00

Add this equation to your foldable.

Note that the left side and right side are equal for the top number and bottom numbers.

Review Nuclear Equations

Alpha decay of Uranium-235.

Beta decay of Uranium-235.

Gamma decay of Uranium-235.

U23592 H

e

42 T

h

23190

U23592 e0

-1 Np23593

U23592 0

0 U23592

Examples of Nuclear Equations

Xe12954

Po21284

Es24399

Ti5222

How to Play Nuclear Decay

Decide who goes first. This person rolls both dice. Starting with Am-241, all players write an

equation for , , or decay that matches the roll on the die.

Players earn points for correct answers The roller earns the # of points from the numbered

die. Everyone else earns 1 point for any correct answer. No points for incorrect answers.

Keep going until you run out of protons or neutrons.

Highest score wins!

Example

Suppose I rolled these dice. I write this equation.

Group member A writes:

Group member B writes:

3

CmeAm 24196

01

24195

CmeAm 24196

01

24195

PueAm 24194

01

24195

Correct!

Correct!

Incorrect!

3 points

0 points

1 point

How to Play Nuclear Decay

Decide who goes first. This person rolls both dice. Starting with Am-241, all players write an

equation for , , or decay that matches the roll on the die.

Players earn points for correct answers The roller earns the # of points from the numbered

die. Everyone else earns 1 point for any correct answer. No points for incorrect answers.

Keep going until you run out of protons or neutrons.

Highest score wins!

Catalyst (5 min) 9/16/11 Half Lives EQ: What is the half-life of a radioactive

isotope?Write equations for:

Alpha decay of Np-237Beta decay of Np-237Gamma decay of Np-237

Use your foldable for help!

What is a half-life?

A half-life is the amount of time it takes for half of the amount of a substance to decay. For example: 241Pu has a half-life of 14 years. Suppose

we start with 100 grams of 241Pu 14 years later, we have 50 grams 28 years later, we have 25 grams 42 years later, we have 12.5 grams…

Band of Nuclear Stability & Half-Lives