1.

Nucleons Protons and neutrons 2. Nuclide A atom in nuclear chemistry. Identified by the number of protons and neutrons -mass number.

3. Ways to identify nuclides: a. 228 88 Ra b. Radium -228

4. Mass Defect and Nuclear Stability The difference between the mass of an atom and the sum of the masses of its protons, neutrons and electrons.

5. Example: Helium-4 2 protons (2 x 1.007276) = 2.014552amu

2 neutrons(2x1.008665) = 2.017330amu

2 electrons(2x.0005486) = .001097amu

total mass = 4.032979amu

The measured mass = 4.00260amu

Mass defect = 4.032979-4.00260=.03038amu

6. Nuclear Binding Energy Convert mass to Kg to match units for energy Kg X meters(squared) / seconds(squared) 1amu = 1.660540 X 10 -27 Kg .03038amu = 5.0446 x 10 -29 Kg E = mc 2 E=(5.0446 x 10 -29 Kg) (3.00 X 10 8 m/s) 2 E = 4.54 x 10 -12 Kg x m 2 /s 2 = 4.54 x 10 -12 J Nuclear Binding Energy = 4.54 x 10 -12 J

Nuclear binding Energy The energy released when a nucleus is formed from nucleons. Can also be thought of as the amount of energy needed to break apart a nucleus. Therefore, the nuclear binding energy is a measure of the stability of a nucleus.

7. Binding Energy per Nucleon The binding energy of the nucleus divided by the number of nucleons it contains

Use pages 701-702 1. Calculate the nuclear binding energy of a Sulfur – 32 atom. The measured atomic mass of Sulfur –32 is 31.972070 amu.

2. Calculate the nuclear binding energy of a Oxygen-16 atom. The measured atomic mass of Oxygen-16 is 15.994915 amu.

3. Calculate the binding energy per nucleon of a Manganese-55 atom. Measured atomic mass is 54.938047amu.

8. Nucleons and Nuclear Stability Band of Stability – stable nuclei clusters over a range of neutron-proton ratios

Radioactive Decay Spontaneous disintegration of a nucleus with emission of particles and/or electromagnetic radiation (nuclear radiation) Radioactive Nuclide unstable nucleus

Types of Radioactive Decay 1. Alpha particles a. Helium -4 b. Both number of neutrons and protons must decrease to stabilize.

• Beta emission- instability in elements above the band of stability occurs because the nucleus has too many neutrons. To decrease the number of neutrons, a neutron can be converted into a proton and an electron. The electron emitted is called a

beta particle.

• Positron emission- elements below the band of stability have too many protons. A proton can be turned into a neutron by emitting a

positron

– a particle that has the same mass as an electron, but has a positive charge and is emitted from the nucleus during some types of radioactive decay.

• Nuclides with too many protons undergo a type of radioactive decay called

electron capture

, an inner orbital electron is captured by the nucleus of its own atom.

• Gamma rays- high energy emr waves emitted from a nucleus as it changes from ground state to excited state.