Isotopes & Isotopes & Radioactive Radioactive

DecayDecay

RadiationRadiationHigh energy rays and particles emitted by High energy rays and particles emitted by radioactive sources. radioactive sources. (most invisible to human eyes)(most invisible to human eyes)

Includes: electromagnetic spectrum, alpha & Includes: electromagnetic spectrum, alpha & beta particles.beta particles.

Electromagnetic SpectrumElectromagnetic Spectrum

RadioactivityRadioactivityThe release of high-energy particles and rays The release of high-energy particles and rays from a substance due to changes in the nuclei from a substance due to changes in the nuclei of its atoms.of its atoms.

Naturally occurring radiation found in our Naturally occurring radiation found in our environment is called:environment is called:

““Natural Background RadiationNatural Background Radiation””

Radioactivity can be useful, such as in medical Radioactivity can be useful, such as in medical diagnoses and treatment (X-rays, Chemotherapy, etc.) diagnoses and treatment (X-rays, Chemotherapy, etc.) and in generating electricity (Nuclear power plants)and in generating electricity (Nuclear power plants)

IsotopesIsotopesAtoms of the same element that have the…Atoms of the same element that have the…– SameSame number of number of protonsprotons (same atomic number) (same atomic number)– DifferentDifferent number of number of neutronsneutrons

Since the number of neutrons differs, the Since the number of neutrons differs, the mass mass number number alsoalso differs differs..– Mass number = protons + neutronsMass number = protons + neutrons

Different isotopes of the same element all have:Different isotopes of the same element all have:– The The samesame chemical chemical symbolsymbol– The The same atomic numbersame atomic number (# of protons) (# of protons)– Different mass numbersDifferent mass numbers

Use standard atomic notationUse standard atomic notation– Symbol + Atomic number + Mass numberSymbol + Atomic number + Mass number

– Also called “Also called “Nuclear SymbolNuclear Symbol””

Representing IsotopesRepresenting Isotopes

XMass #

Atomic #

K 41

19

e.g.:e.g.: Potassium has 3 naturally occurring Potassium has 3 naturally occurring isotopes.isotopes.

K 40

19K 39

19

Potassium-39Potassium-39 Potassium-40Potassium-40 Potassium-41Potassium-41

ProtonsProtons

NeutronNeutronssElectronElectronss

1919

2020

1919

1919

2121

1919

1919

2222

1919

In nature, most elements are found as a mixture of isotopes.In nature, most elements are found as a mixture of isotopes.

Atomic MassAtomic Mass

Potassium-39Potassium-39 Potassium-40Potassium-40 Potassium-41Potassium-41

93.26% 93.26% 0.01% 0.01% 6.73% 6.73%

Each banana has the same relative abundance of potassium isotopesEach banana has the same relative abundance of potassium isotopes

The atomic mass of an element is the average of all The atomic mass of an element is the average of all the naturally occurring isotopes.the naturally occurring isotopes.

Atomic mass = Atomic mass = (.9326 x 39) + (.0001 x 40) + (.0673 x 41)(.9326 x 39) + (.0001 x 40) + (.0673 x 41)= 39.1= 39.1

Classwork:Classwork: Practice Problems Q. 1-4Practice Problems Q. 1-4Page 291Page 291

““Isotopes” WorksheetIsotopes” Worksheet

HomeworHomework:k:

““Isotopes and Ions” Isotopes and Ions” WorksheetWorksheet