Physical Science. Sec 1: What is radioactivity? So what are the names of these particles? Positive...

Physical Science

So what are the names of these particles?

Positive particles?

protons

neutrons

No charge, NEUtral

Bell ringer review: What is this structure made up of protons and neutrons?

protons

neutrons

Atomic nucleus

What element is this? How do you know?1.Count the number of protons. 2.The # of protons = the __________?

2

What element is this? How do you know?1.Count the number of protons. 2.The # of protons = the Atomic Number

2

2

He4

Complete the table to indicate how many protons and neutrons there are.

P3215

Remember, the bottom # is the # of protons (+), or the atomic number. (Verify this on the periodic Chart.


P3215The top number is

the mass number, or the atomic mass.

Mass # = protons + neutronsso

Mass # - protons = neutronsOR

Mass # - atomic # = neutrons


protons neutrons

15 17

Remember in chemical reactions there were always the same number of each type of atoms on each side of the arrow?

2H2 + 02 → 2H2OAtoms were just rearranged.

4 H atoms

Remember in chemical reactions there were always the same number of each type of atoms on each side of the arrow?

2H2 + 02 → 2H2OAtoms were just rearranged.

2 O atoms

Balanced equation

But what would happen if an atom actually lost protons?

P3215 ?1330

The atomic number would change!

Change number of p+ means change in mass number too!

But what would happen if an atom actually lost protons?

P3013 ?

Note the change in atomic number.So the identity of the element will change!!!!

Al3013

This is radioactivity!Radioactivity - the process by which an unstable nucleus emits one or more particles or energy in the form of electromagneticradiation.

- there are different types of radiation- this is only one example.

This is radioactivity!Radioactive Decay – the process by which an atomic nucleus loses nuclear mass• becomes an isotope by losing neutrons • becomes a different element by losing protons

Nuclear radiation the particles that are released from the nucleus during radioactive decay.

Page

4 Types Nuclear

Radiation

You won’t need to memorize these values but you will need to know relative size.

I. Alpha Particle1. Made of 2 protons and 2 neutrons2. Charge of +23. Mass of 4 amu4. Symbolized by - Basically it is a helium nucleus5. Low energy, least penetrating form of radiation, stopped by sheet of paper or skin6. Inside body can cause damage to bio-molecules. (Proteins, DNA)7. Used in smoke detectors: 241Am

(Alpha symbol)

Alpha Particle8. Alpha Decay –atom loses 2 protons & 2 neutrons.•Loss of mass results in new mass number. •Loss of protons results in new element.•An equation can be written:

Pu240

94 U236

92He +42

Writing equations for Alpha DecayStep 1: Write the nuclide notation for your starting material,Step 2: Write the nuclide notation for the particle released.

Pu240

94 He 42


Pu240

94 He 42

Step 3: Subtract the atomic mass units lost. 240 – 4 = 236

+236


Pu240

94 He 42

Step 3: Subtract the atomic mass units lost. 240 – 4 = 236 Step 4: Subtract the protons lost. 94 – 2 = 92

+23692


Pu240

94 He 42

Step 3: Subtract the atomic mass units lost. 240 – 4 = 236 Step 4: Subtract the protons lost. 94 – 2 = 92Step 5: Look up the new identity of the element and write the symbol.

+23692 U

Atomic number

When one element turns into another element by the process of radioactive decay this is called

transmutation

Pu240

94 He 42

+23692 U

Anti-nutrino

II. Beta decay1. A neutron turns into a proton and emits an electron!

e-This electron is called a Beta particle

Symbol -

Anti-nutrino

II. Beta decay1. A neutron turns into a proton and emits an electron!

e-This electron is called a Beta particle

Symbol -

You could draw a picture of the change that looked like this.

II. Beta decay1. A neutron turns into a proton and emits an

electron!2. Beta particle symbol: e or -

3. Charge: negative4. Mass = 0 so the nuclide mass stays the

same.5. Higher energy that alpha particles, can pass

through paper but stopped by aluminum foil.6. Inside the body will damage cells.7. Overall gain of one proton so transmutation

has occurred.

0-1

7. Overall gain of one proton so transmutation has occurred. Example:

C14

6 e 0

-1 +14

7. Overall gain of one proton so transmutation has occurred. Example:

C14

6 e 0

-1 +147 N

Remember you are subtracting so 6 – (-1) = 6 + 1 = 7

Keep in mind that there is another type of Beta decay called Positron emission – you’ll learn about it in chemistry but we won’t worry about it right now.

Free

Informatio

n

III. Gamma Rays1.symbol:2.Electromagnetic rays (not matter)3.The highest energy and shortest wavelength of the entire spectrum.

Rays have enough energy to penetrate skin, paper and even wood. Usually contained by concrete lined with lead.

III. Gamma Rays1.symbol:2.Electromagnetic rays (not matter)3.The highest energy and shortest wavelength of the entire spectrum.4.No mass or charge.5.Travel at the speed of light.6.May not cause as much damage to tissues because they do not carry a charge.7.Useful in treating cancers by directing a beam of radiation at tumors.• 99Tc most widely used radio-isotope in

medicine.

III. Gamma Rays8. Transmutation does not occur by gamma emission.

IV. Neutron emission1. high energy neutrons emitted from a

nucleus.2. Neutron is matter and has mass3. Relatively high energy, between beta and

gamma particles, can penetrate concrete4. occurs in heavy isotopes (He-5) and high

mass radio active elements (Cf-252)

IV. Neutron emission8. Transmutation does NOT occur . . . but change in

mass number does due to loss of neutron.

Physical Science. Sec 1: What is radioactivity? So what are the names of these particles? Positive...

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