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What Would You See if you Were On a Nucleus?. Topics for Today. Elements and Atoms and Molecules, oh boy Inside the Atom Mass Number and Isotopes More on Radon. Readings in Text. 1.7 Atoms & Molecules 2.2 Atomic Structure and Periodicity. Topics for Friday.

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What Would You See if you Were On a Nucleus?


Topics for Today

  • Elements and Atoms and Molecules, oh boy

  • Inside the Atom

  • Mass Number and Isotopes

  • More on Radon


Readings in Text

1.7 Atoms & Molecules

2.2 Atomic Structure and Periodicity


Topics for Friday

  • Quiz #1 at the end of the period.

  • You can find the practice questions on the course website (News of the Week on the Monthly Calender).


  • What is radiation? How do radioactive substances behave?


Topics for Friday

  • Radiation

  • History and discovery of radioactivity

  • Alpha, beta, and gamma decay

  • Quiz #1


Readings

  • Chapter 2 on the electromagnetic spectrum (page 75)

  • Chapter 7.7 - What is radioactivity?

How are gamma rays different than visible light? How are they similar?


Announcements

  • Assignment #1 is due in your TA’s email Inbox Monday before lecture!

  • Please send to your TA and myself!

  • See the course website for the full details!


PRELAB QUIZ for Week #2

Due before your lab

next week

Unlimited number of tries allowed this week only.


Topics for Today

  • Elements and Atoms and Molecules, oh boy

  • Inside the Atom

  • Mass Number and Isotopes

  • More on Radon


Handout


ELEMENT:

Eleven elements make up over 99% of your body.

Which ones?


Chapter 11 (page 488)

  • Elements in the human body

    Figure 11.3 and Table 11.2

Which compound

is most abundant in

your body?


Rn

86

Review - Elements

  • One of the hundred or so symbols on the periodic table.

  • Which ones do you need to know?


Interlude


An atom is the smallest particle of an element that we can identify as the element.

Can we SEE atoms?


Microscopes


Copper Surface

Scanning Tunneling Microscope


  • What is wrong with this picture?


  • What is wrong with this picture?

  • How big are these atoms?


Short Answer

The diameter is around 1 to 5 x 10-10 meters

Or 0.0000000001 meters!

How small is this?


Powers of 10 Website

  • http://molecular.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html


  • A pinhead is about 1 x 10-3 meters (1 mm) in diameter

  • Therefore, more than 1,000,000 atoms can fit across a pinhead!


~3 x 10-10 meters

in diameter

(~300 x 10-12 meter)


~3 x 10-10 meter

  • The nucleus is about 1/100,000 of the diameter.


Back to the Pinheads

  • What if the nucleus had a diameter of a pinhead (1 mm)?


Back to the Pinheads

  • What if the nucleus had a diameter of a pinhead (1 mm)?

How big would the atom be?


Back to the Pinheads

  • What if the nucleus had a diameter of a pinhead (1 mm)?

How big would the atom be?

10 meters!


If the nucleus were 10 cm in diameter, then…

the edge of the atom would be 1,000,000 cm or

10,000 meters or

6 miles away!

10 cm


If the nucleus were 10 cm in diameter, then…

the edge of the atom would be 1,000,000 cm or

10,000 meters or

6 miles away!

10 cm

SO, what would you see if you were on the nucleus?


  • A whole lot of empty space…


What is in an atom?


Charge Location Mass


Where is the mass located?

Charge Location Mass


Charge Location Mass

What gives an atom its volume?


Back to Radon…

Atomic Number (protons), Z


X

A

Z

How else can we write this?

X = Element Symbol from periodic table

A = Mass number (protons + neutrons)

Z = Number of Protons


X

A

Z

How else can we write this?

Try this for radon-222!

X = Element Symbol from periodic table

A = Mass number (protons + neutrons)

Z = Number of Protons


222

86

Rn

radon-222


For the quiz…

  • Calculators are OK. Cannot use any calculators with memory!


Quiz Cont…

  • Please sit ONLY in the ‘dark’ colored seats!


Back to the Atom…


222

86

Rn

radon-222

Is this needed?


222

86

Rn

222Rn

radon-222

How about this?


224

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223

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222

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221

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Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

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These are the _______ of radon.

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

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These are the isotopes of radon.

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

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What do these isotopes have in common?

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

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How do they differ?

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All the atoms of an element have the same number of ___________,

… but the isotopes of an element differ in the number of ___________.


Remember This!!

All the atoms of an element have the same number of protons,

… but the isotopes of an element differ in the number of neutrons.


All the atoms of an element have the same number of protons,

… but the isotopes of an element differ in the number of neutrons.

How else are the isotopes similar?


All the isotopes react in the same way.

2 H2 + O2 2 H2O


All the isotopes react in the same way #1.

2 H2 + O2 2 H2O


Hydrogen

Atomic Number (protons)

Atomic Mass


A Word of Caution…


  • The mass number (A) is NOT found on the periodic table

  • The periodic table shows us atomic mass!


  • Atomic Mass = Average of all of the Mass Numbers in found in nature


1

1

H

1H

hydrogen-1


Isotopes of hydrogen

1H or H “hydrogen”

2H or H or D deuterium

3H or H or T tritium

1

1

2

1

3

1


Isotopes

1

1

1H or H “hydrogen”

2H or H or D deuterium

3H or H or T tritium

2

1

3

1

How many neutrons does 3H have?


Which isotope is deuterium?

hydrogen

deuterium

p

p

n

n

n

p

tritium


Which isotope is deuterium?

hydrogen

deuterium

p

p

n

Deuterium

Hydrogen

n

n

p

tritium

Tritium


Since we are on hydrogen….

Does the little 2 after hydrogen have anything to do with isotopes?

2 H2 + O2 2 H2O


H2 = hydrogen molecule

made up of 2 hydrogen atoms


Is H2 an atom or a compound?

H2 = hydrogen molecule

made up of 2 hydrogen atoms


Does the BIG 2 before hydrogen have anything to do with isotopes?

2 H2 + O2 2 H2O


  • 2 H2 means 2 hydrogen (H2) molecules


Isotopes of hydrogen

1H or H “hydrogen”

2H or H or D deuterium

3H or H or T tritium

1

1

2

1

3

1


D2O vs H2O

Does D2O freeze just like water?


Back to protons and neutrons …

Mass number

(A)

Atomic number

(Z)

2

1

H


ONE of the isotopes of _______.


ONE of the isotopes of chlorine.


Try this on your own


Remember!

Mass # = Atomic # + # neutrons


224

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223

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222

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221

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And back to isotopes …

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

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Isotopes

1) EVERY element on the periodic table has different isotopes.


Isotopes of hydrogen

1H or H “hydrogen”

2H or H or D deuterium

3H or H or T tritium

1

1

2

1

3

1


Carbon

12

6

12C or C

13C or C

14C or C

13

6

14

6


Carbon

12

6

98.89%

1.11%

Trace

12C or C

13C or C

14C or C

13

6

14

6

What can people find out from isotopes?


When / How did life start on Earth?

12

6

98.89%

1.11%

Trace

12C or C

13C or C

14C or C

13

6

14

6


When / How did life start on Earth?

12

6

98.89%

1.11%

Trace

12C or C

13C or C

14C or C

13

6

14

6

We’re talking over 4 billion years ago!


Remember…

All the isotopes react in the same way.


Carbon-12 vs Carbon-13

Most living things depend on carbon for their livelihood…

Photosynthesis and respiration, for example


Carbon-12 vs Carbon-13

Most living things depend on carbon for their livelihood…

But do they use all carbon isotopes equally?


Carbon-12 vs Carbon-13

  • Living organisms can use 12C easier than 13C.

  • Remains of early organisms (fossil fuels, coal) tend to be rich in 12C while rocks are rich in 13C.

But do they use each isotope equally?


Isotopes

Some elements have stable isotopes. Some elements have only radioactive isotopes.

Can you tell from the periodic table?


224

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223

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222

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221

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All radioactive!

No stable isotopes

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

Rn Rn Rn Rn

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  • Watch out for the word “stable”.

    Stable vs. radioactive

    Stable vs. chemically reactive


Isotopes

3) Isotopes are naturally abundant in different concentrations


1H “hydrogen” 99.985%

2H deuterium0.015%

3H tritium trace amount


Was there any D2 or T2 in these balloons?

H2 H2 + O2


Isotopes

4) Behave almost IDENTICALLY in chemical reactions


Chemical Reactions

2 H2 + O2  2 H2O

2 D2 + O2  2 D2O

2 T2 + O2  2 T2O


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