Atoms in a Nutshell

All matter is made up of tiny particles called atoms.

• There are about 92 naturally occurring elements. (The elements with numbers over 92 are man made.)

• Atoms are made up of three main sub-atomic particles.– Protons– Neutrons– Electrons

Protons and neutrons are found in the center of the atom. (Nucleus)

Electrons are tiny particles that zoom around the space OUTSIDE the nucleus.

Particle Mass

(AMU)

Charge

Protons 1 +

Neutrons 1 Neutral

Electrons Insignificant

1/1800th-

Reading the Periodic Table

19 K 39

Atomic Number

Atomic Mass

Atomic number

Tells the number of protons and electrons

Atomic Mass

Tells the number of protons and neutrons added together.

Atom Models

Protons and Neutrons are found in the center of the atom. We call the area with the protons and neutrons the nucleus.

Electrons are found zooming around the outside. They are in different energy levels.-Inner level has space for 2 electrons.-2nd level has space for 8 electrons.-3rd level has space for 18 electrons

**More on electrons later. This is just the bare bones for smaller elements with 18 electrons or less.

Which Element is this?

• Atomic #

• Atomic Mass

• Valence

Electrons

Which Element?

Which Element?

Lewis ModelShows only the electrons in the outermost level. – Called “Valence Electrons”

– Valence Electrons determine how elements react.

– Write the symbol with 1 – 8 dots around it.

Lewis ModelShows only the electrons in the outermost level. – Called “Valence Electrons”

– Valence Electrons determine how elements react.

– Write the symbol with 1 – 8 dots around it.

Rutherford LabPurpose: to mimic Rutherford's famous gold foil experiment.

Materials: marble (alpha particle), cardboard models, plain paper, ruler.

Procedure: [Summarize procedure in 2 – 3 sentences]

1. Pick up a piece of plain paper from the supply area.

2. Center the paper on top of a cardboard model and tape it down to keep it in place. Don’t look under the box!

3. Roll the marble under one side of the box. Observe where the marble comes out and trace the approximate path on the white paper.

4. Working from all four sides of the black box, continue to roll the marble under the board, making observations and tracing the rebound path for each marble roll. Roll the marble at least 20 times from each side of the box. Vary the angles at which the marble is rolled into the box.

5. After sketching the apparent path of the marble from all sides and angles, the general size and shape of the unknown target should emerge in negative form from the area where there are no lines.

6. Form a working hypothesis of the unknown target by sketching the shape on your plain paper. Based on your hypothesis, repeat as many marble rolls as necessary to either confirm or revise your structure.

Data:

Make a 10 X 10 cm square to record your data.

Rutherford Lab ConclusionAnalysis:

1. Skim pages 111 to 112 in the textbook. In what ways does this activity simulate Rutherford’s experiment?

2. Briefly describe Rutherford’s experiment and what he observed.

3. As a result of his observations, what did Rutherford conclude about the structure of the atom?

Isotopes• Isotopes are atoms with the same

number of protons but different number of neutrons

• Most elements have several different isotopes.

– Different isotopes have different masses because they have different numbers of neutrons

– Isotopes that are unstable will give off radiation.

Hydrogen has 3 isotopes

Using Symbols to show isotopes

A = mass number

(the total number of protons + neutrons)

Z = atomic number

(the total number of protons)

X = element symbol

A

ZX

Isotopes

Definition

Examples of 2 or more

Steps showing how average

atomic mass was calculated.

Venn Diagram comparing

contrasting 2 isotopes

36

17 Cl

Grades and AveragesCategory Points Percent Weighted Average

Homework 390/400 =.975 =97.5%

A

Homework = 15% of grade.15 X 97.5 = 14.62

Labs 200/235 =.85 = 85%

B

Labs = 25% of grade.25 X 85 = 21.25

Test/Quiz 210/300 =.70 = 70%

C-

Tests/Quizzes = 60% of grade.6 X 70 = 42

14.6221.2542.00

Chocolate-chipium LabIsotope Number Percent Relative Mass

% X Chip Mass

Mini 100 100/122 = .82 .82 X .1 = .082

Mid-size 20 20/122 = .16 .16 X .5 = .08

Kisses 2 2/122 = .02 .02 X 4.7 =.09

122 100% .082+.08+.09=.252

Atomic Mass

Magnesium has three isotopes.

• 78.99% magnesium 24 with a mass of 23.9850 amu,

• 10.00% magnesium 25 with a mass of 24.9858 amu,

• 11.01 magnesium 26 with a mass of 25.9826 amu.

• What is the atomic mass of magnesium?

IsotopePercent

AbundanceMass

Mg-24 78.99 23.9850 18.94575

Mg-25 10.00 24.9585 2.49585

Mg-26 11.01 25.9826 2.86068

24.304 amu

Atomic Mass

Calculate the atomic mass of copper if copper has two isotopes. 69.1% has a mass of 62.93 amu and the rest has

a mass of 64.93 amu.

Copper for amu 63.548 A.A.M.

amu 20.06337 amu 43.48463 A.A.M.

amu) .93(0.309)(64 amu) .93(0.691)(62 A.A.M.

=

+=

+=

Cu29

63.548

IsotopePercent

AbundanceMass

Cu-63 69.1 62.93 43.48463

Cu-65 30.9 64.93 20.06337

63.548

Warm-Up1. Magnesium consists of three

naturally occurring isotopes. The percent abundance of

these isotopes is as follows:

24-Mg (78.70%)

25-Mg (10.13%)

26-Mg (11.7%).

-Bohr and Lewis dot models due end of class.

Homework- Due Tuesdaypages 123 – 126

1. Describe how the periodic table was developed.

2. What criteria did Mendeleev use to arrange it?

3. Which elements are the “representative” elements?

-Read “Ask an Artifact for a Date”

1. Radiometric dating is based on two important facts. What are they?

2. Write the symbols for 3 common isotopes of carbon.

3. What is half-life?

4. The half-life of carbon – 14?

5. How is the half-life of carbon 14 used to determine the age of objects?

6. Why can’t they use carbon dating on objects older than 40, 000 years

-Isotope Posters -Quiz Friday

•Isotopes

•Using percent abundance to determine average atomic mass

•Bohr and Lewis Dot models

10/ /2012 1. Make a Bohr and Lewis Dot model for this element.

-Isotope Posters due Wednesday

-Wednesday

Practice Test

-Quiz Friday•Isotopes

•Protons, Neutrons and Electrons

•Using percent abundance to determine average atomic mass

•Bohr and Lewis Dot models

HW Quiz Chap 5

1. The charge on a proton is ________, while the charge on neutrons is ______

2. Thomson is associated with _______, while Rutherford is associated with ________. (Fill in subatomic particle.)

3. How are isotopes of the same element alike? _________________

4. How can the atomic number and atomic mass be used to find the numbers of protons, neutrons and electrons?