Lec: Isotopes and Ions

An Isotope is an element that has the same number of protons but a different number of neutrons.

Example: C12,C13, and C14 have 6 protons but 6, 7, and 8 neutrons. The combination of the # of protons and neutrons equals the isotope #.

The nuclei of C12,C13, and C14

C12 = 6 protons 6 neutrons

C13 = 6 protons 7 neutrons C14 = 6 protons 8 neutrons

Protons= Neutrons=

C12 C1

3

C14

Determine what isotope is the atom below. Express you answer as an isotope number.

F19

9 Protons and 10 neutrons

Ion: An atom that has an electrical charge due to the increase or decrease of electrons.

All protons have a +1 electrical charge.All electrons have a -1 electrical charge.If an atoms protons and electrons are the same the atom is neutral.

An ion with a negative (-) electrical charge is an anion.

Examples of anions are expressed like this:

F- or C-2

Fluorine (F) has gained an electron thus changing F to a (-1) electrical charge. Carbon (C) has gained two electrons thus changing the electrical charge to -2.

Example of an ion for F-

Fluorine according to your PTE should have 9 electrons and protons however F- has 10 electrons and 9 protons.

An ion with a positive (+) electrical charge is an cation.

Examples of cations are expressed like this:

Li+ or C+2

Lithium (Li) has lost an electron thus changing Li to a (+1) electrical charge. Carbon (C) has lost two electrons thus changing the electrical charge to +2.

Example of cation for Li+

Lithium according to your PTE should have 3 electrons and protons however Li+ has 2 electrons and 3 protons.

Lec: Types of Radioactive Decay and Half-Life

Alpha Particle DecayBeta Particle DecayGamma ray

Alpha Particle Decay

A positively charged helium (He+2) nuclei traveling at a high speed.

Beta Particle Decay

A negatively charged electron particle that travels at a high speed.

The mass of an alpha particle is almost 8000 times more than a beta particle.

Gamma RayAn electromagnetic wave similar to X-rays. It can not be detected by your eyes. Gamma rays move at the speed of light.

Half-Life: The time it takes for a radioactive isotope total mass to decay by one half. A half-life can be anywhere from fractions of a second to millions of years. Example: U238 has a half-life over 4.5 billion years and Po214 is 0.0000016 second.

The half-life of Ra222 at the end of 0 half life. 100% still radioactive radon.

0102030405060708090

100

%

0 1 2 3 4

Half-Life

Polonium 214Radon 222

The half-life of Ra222 at the end of 1st half life. 50% still radioactive radon.

0102030405060708090

100

%

0 1 2 3 4

Half-Life

Polonium 214Radon 222

The half-life of Ra222 at the end of 2nd half life. 25% still radioactive radon.

0102030405060708090

100

%

0 1 2 3 4

Half-Life

Polonium 214Radon 222

The half-life of Ra222 at the end of 3rd half life. 12.5% still radioactive radon.

0102030405060708090

100

%

0 1 2 3 4

Half-Life

Polonium 214Radon 222

The half-life of Ra222 at the end of 4th half life. 6.25% is still radioactive radon.

0102030405060708090

100

%

0 1 2 3 4

Half-Life

Polonium 214Radon 222

Calculating the half-life of Ra222. Ra222 has a half-life of 4 days and starting mass of 800g.

# of half lives

Time %Radioactiv

e

Mass radioacti

ve

0

1

2

3

4

0 half life

# of half lives

Time %Radioactiv

e

Mass radioacti

ve

0 0 days 100 800 g

1

2

3

4

1st half life

# of half lives

Time %Radioactiv

e

Mass radioacti

ve

0 0 days 100 800 g

1 4 days 50 400 g

2

3

4

2nd half-life

# of half lives

Time %Radioactiv

e

Mass radioacti

ve

0 0 days 100 800 g

1 4 days 50 400 g

2 8 days 25 200 g

3

4

3rd half-life

# of half lives

Time %Radioactiv

e

Mass radioacti

ve

0 0 days 100 800 g

1 4 days 50 400 g

2 8 days 25 200 g

3 12 days 12.5 100 g

4

4th half-life

# of half lives

Time %Radioactiv

e

Mass radioacti

ve

0 0 days 100 800 g

1 4 days 50 400 g

2 8 days 25 200 g

3 12 days 12.5 100 g

4 16 days 6.25 50 g

Bismuth, Bi214 has a half-life of 20 minutes, how much will still be radioactive when it reaches its 4th half-life and when will this occur? The starting radioactive mass is 200g.

4th half-life# of half

livesTime %

Radioactive

Mass radioacti

ve

0 0 minutes

100 200 g

1 20 minutes

50 100 g

2 40 minutes

25 50 g

3 60 minutes

12.5 25 g

4 80 minutes

6.25 12.5 g

The Last Lecture For This Unit.

Bismuth-210

# of half lives

Time %Radioactiv

e

Mass radioacti

ve

0 0 days 100 64 g

1 5 days 50 32 g

2 10 days 25 16 g

3 15 days 12.5 8 g

4 20 days 6.25 4 g