Radiation can be separated into different types by passing neared charged plates. Negatively charged particles are deflected towards the positive plate, and positive particles towards the negative plate.

Alpha () particles have the most charge and mass. They interact most with matter by ionizing it. This slows them, and they are the most easily stopped. Beta () particles can be stopped by a sheet ofaluminum. Gamma () radiation has the most penetrating power.High density materials like lead are required to stop it.

III. When nuclei decay, they emit ____ basic types of radiation (or particles).

Name symbol notation

1. alpha particle or

2a. beta particle (electron) - or

2b. positron + or

3. gamma radiation

He4

24

2

e0

-10

-1

3

e01

01

00

1. Alpha Decay is the emission of an alpha () particle:a/ It is a He nucleus.b/ It contains 2 p and 2 n. charge: +2 mass: 4 amu

Ex. The decay of Ra-226 into Rn-222 occurs naturally because Ra-226 is radioactive.

decaysinto

All nuclear equations, like the one given above,must be balanced (the same on the left and right).

Ra88

226 Rn86

222 + He2

4

Conservation of mass: No mass is lost.Total mass before decay = Total mass after decay Mass numbers (superscripts) must add up:

= +

Conservation of charge: No charge is lost.Total charge before decay = Total charge after decay Atomic numbers (subscripts) must add up:

= +

226 222 4

88 86 2

The Radium Girls (1917):They painted watches with “glow in the dark” radium. The women, who had been told the paint was harmless, ingested deadly amounts of radium by licking their paintbrushes to sharpen them; some also painted their fingernails with the glowing substance.

2a. Beta Decay is the emission of a beta () particle:a/ It is exactly the same as an electron

charge: -1 mass: 1/1800 amu ≈ 0b/ The electron is emitted from the nucleus when a neutron decays into a proton and an electron:.

n0

1 p1

1 + e-1

0

Ex. Pb-214 decays into Bi-214

Pb82

214 Bi83

214 + e-1

0

Conservation of mass:The mass of the electron is ignored because it is so small compared to the n and p masses.mass numbers add up:

= +

Conservation of charge:atomic numbers (subscripts) must add up:

= +

214 214 0

82 83 -1

Google imagesof depleted uranium:

Normal uranium:99.3 % U-238.7 % U-235is separated so thatonly about .4%U-235 remains.

2b. Positron emission from the nucleus occurs when a proton decays into a neutron and a positron (+):

A + is a positive electron. It is an example of antimatter. It has

a/ the same mass as an electron, but b/ opposite charge (same charge as a proton)

charge: +1 mass: 1/1800 amu ≈ 0

Ex. Potassium K-37 decays into argon Ar-37

p1

1 n0

1 + e+1

0

K1937 Ar

18

37 + e+1

0

Conservation of mass:Like the electron, mass of the positron is ignored .The mass numbers add up:

= +

Conservation of charge:atomic numbers (subscripts) must add up:

= +

Positrons and electrons annihilate each other (their matter is transformed into energy) if they collide.

K1937 Ar

18

37 + e+1

0

37 37 0

19 18 +1

0

0

3. _________ () radiation is also called rays. a/ They are high-energy particles of _______.

visible light: gamma ray:

b/ They have no __________ and no _________ .symbol:

c/ rays are not always shown in nuclear reactions.

Gammalight

charge mass

III. When nuclei decay, they emit ____ basic types of radiation (or particles).

Name symbol notation

1. alpha particle or

2a. beta particle (electron) - or

2b. positron + or

3. gamma radiation

He4

24

2

e0

-10

-1

3

e01

01

00