1. Isotopes and Radioactivity

2. OUTCOME QUESTION(S): C12-2-04 ENERGY AND ATOMIC MODELS
Explain average atomic mass using isotopes and their relative abundance.
Include: radioisotopes
Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy.
Include: Plank’s Equation, quantum, photon
Understand the historical development of the Quantum Mechanical Model of the atom.
Describe how unique line spectra are created for each element.
Include: Bohr model
Vocabulary & Concepts
Radioisotope Radioactive decay
Half-life

3. BUT atoms can gain or lose electrons forming IONS+1 +3 -3 -2 -1 +2
+4/-4
We use the proton number (atomic number) to identify elements since protons are not gained or lost

4. The atomic number (Z) is the number of protons in the nucleus of an atom - identifies an element.
The atomic mass (A) is the number of protons plus the number of neutrons.
There are many element notations – just remember the mass is always the bigger number

5. Isotopes: Atoms with the but a different number of neutrons.
same number of protons
Hydrogen
Atomic Mass = 1
Atomic Number = 1
RA: %
Deuterium
Atomic Mass = 2
Atomic Number = 1
RA: 0.015%
Relative Abundance (RA): Percentage of that isotope that would appear in an average sample.
Atomic mass on the Periodic Table is actually an average of isotopes of an element based on relative abundance in nature

6. Isotopes are VERY common

7. Mass spectrometer determines the mass of individual atoms or isotopes.
Sends atoms through a magnetic field which bends their paths.
The heavier the atom – the less it bends

8. 1. 19 protons and 20 neutrons - mass number of 39
Potassium isotopes:
protons and 20 neutrons - mass number of 39
(potassium K RA: 93.26%)
protons and 21 neutrons - mass number of 40
(potassium K RA: 0.012%)
protons and 22 neutrons - mass number of 41
(potassium K RA: 6.730%)
Notice how the atomic mass (A) is used in the notation to show which isotope is being referred too

9. Convert the RA percent to a decimal
Magnesium exists as three isotopes in the world:
78.99% is 24Mg ( μ)
10.00% is 25Mg ( μ)
11.01% is 26Mg ( μ)
Convert the RA percent to a decimal
Calculate the average atomic mass of magnesium:
(0.7899)( μ) = μ +
(0.1000)( μ) = μ
= μ
(0.1101)( μ) = μ
Sum the results

10. Rubidium has two common isotopes, 85Rb and 87Rb
Rubidium has two common isotopes, 85Rb and 87Rb. If the abundance of 85Rb is 72.2% and the abundance of 87Rb is 27.8%, what is the average
atomic mass?
72.2% is 85Rb (85 μ)
27.8% is 87Rb (87 μ) +
(0.722)(85 μ) = μ
= μ
(0.278)(87 μ) = μ

11. helium He 6He
The nucleus of many isotopes are unstable and break apart over time - radioactivity.

12. Radioisotopes - unstable nuclei releasing energy and/or particles.
Release of energy is called radioactive decay.
Half-life - amount of time it takes for half the radioisotope to be converted into another particle.
Atoms may be converted into another isotope of the same element or a completely different element

13. Many different types of decay exist: alpha decay, beta decay, gamma decay…

14. Notice many different types of decay take place.
This is called a decay chain – it shows the products of the radioactive decay of an element.
Notice many different types of decay take place.
This is like real alchemy…

15. C12-2-04 ENERGY AND ATOMIC MODELS
CAN YOU / HAVE YOU?
C ENERGY AND ATOMIC MODELS
Explain average atomic mass using isotopes and their relative abundance.
Include: radioisotopes
Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy.
Include: Plank’s Equation, quantum, photon
Understand the historical development of the Quantum Mechanical Model of the atom.
Describe how unique line spectra are created for each element.
Include: Bohr model
Vocabulary & Concepts
Radioisotope Radioactive decay
Half-life