Entry Task: Oct 5th Friday

Question:

1. What physical characteristics do these two models of an atom have in common?

2. How do the two models differ?

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Agenda:

• Sign off on Ch. 4 sec. 1-3 ws• Notes on protons, neutrons &

electrons and Isotopes• HW: Isotope worksheet

Protons

Electrons

Protons Electrons

I can…

• Explain the relationship between proton, electron and neutrons with atomic number and atomic mass.

• Define an isotope and explain why atomic masses are not whole numbers

Atomic Number

• Is the number of protons in the nucleus.

• Atomic # = # of protons = # of electrons

Mass Number

• Is the sum of the number of protons + neutrons in the nucleus of an atom.

6

C12.001

# of protons

# of protons # neutron

Using a Periodic TableElement # of

protons# of

electrons# of

neutronsAtomic mass

Atomic number

Helium

Sodium

Sulfur

Silver

Plutonium

2 2 2 4 2

11 11 12 23 11

16 16 16 32 16

47 47 61 108 47

94 94 150 244 94

Atom Atomicmass

Atomic Number

# Protons

# Electrons

# Neutrons

92 52

55 75

201 80

33 40

4040 40Zirconium

55 55130Cesium

8080 121Mercury

33 3373Arsenic

You Try…

Isotopes

Lets say that massed and recorded 100 pennies.

And the following is the data that you recorded.

1994 U.S. Pennies

90 of the pennies have a mass of 2.63 grams

5 of the pennies have a mass of 2.60 grams

5 of the pennies have a mass of 2.67 grams

What can you deduce from this information?

The information gained is:

90% of all 1994 pennies will have a mass of 2.63 grams

5% of all 1994 pennies have less mass of 2.60 grams

5% of all 1994 pennies have more mass of 2.67 grams

10% of the pennies have more or less metal in them.

What are isotopes?

• Isotopes are elements with the same number of protons and electrons but the number of neutrons differ from the average amount.

Isotopes are the same as the pennies but with a particular element

It’s an atom that has more or less the average number of neutrons in the nucleus of an atom

OR

How can scientist “weigh” an atom?

Scientist can’t “weigh” an atom. But they can determine the mass of an atom by how it behaves.

So how do they do it… lets look at an analogy.

Imagine a race track that bends at a 90° angle.Take 3 cars- all going the same speed

What can be assumed by the weight/mass of the pink car?

Too heavy to make the turn

What can be assumed by the weight/mass of the blue car?

Too light to make the turn

What can be assumed by the weight/mass of the orange car?

Its mass was enough to make the turn.

Scientist use a mass spectrometer

• It is the “race track” for atoms.

• The atoms are the “cars”

Atomic weight measurements

From the mass spectrometer, clearly there are more neon atoms with a mass of 20.

The next is 22 and lastly is 21.

How do you know if its an isotope

The periodic table records the

AVERAGE atomic mass.

If a given atomic mass for a particular element is NOT on the periodic table- You have an ISOTOPE

Sulfur-34Sulfur is the element

The atomic mass is 34

Look on periodic table- its mass is listed as 32

Is it an isotope?

Yes- it is an isotope

How many protons, electrons and neutrons does this atom have?

16+ 16- 18ø

Name Atomic Mass

Atomic Number

Number ofProton

Number of Electrons

Number ofNeutron

Lithium-8

Gallium-67

Thallium-201

Lead-208

3 3 58 3

67 31 31 3631

81201 81 12081

208 82 82 12682