Chapter 4

Chapter 4 Terms 1.Atom 2.Electron 3.Nucleus 4.Proton 5.Neutron 6.Atomic number 7.Isotope 8.Mass number 9.Atomic mass 10.Radioactivity 11.Alpha radiation 12.Alpha particle 13.Beta radiation 14.Beta particle 15.Gamma ray

Chapter 4.2 Subatomic Particles and the Nuclear Atom

The Atom Nucleus Electron cloud The Atom is the smallest particle of an element that retains the properties of that element.

 Protons (p + )  + 1 electrical charge  Mass ~1  Electrons (e - )  -1 electrical charge  Mass ~ 1/2000  Neutrons (n 0 )  no electrical charge  Mass ~ 1A The Atom

protons and neutrons are in the nucleus. the number of electrons is equal to the number of protons. electrons in space around the nucleus. The atom is mostly empty space The Atom

Chapter 4.3 How Atoms Differ

Atomic Number, Z All atoms of the same element have the atomic number, Z 13 Atomic number

protons determine the identity of an element, and its chemical and physical properties. The atomic number = number of protons Atomic Number, Z

Z = # protons = # electrons Atomic Number, Z

Mass Number, A  A carbon atom with 6 protons and 6 neutrons = 12 atomic mass units # p + + # n 0 = Mass Number (A)

Neutrons & Isotopes # n 0 = A – Z

STOP Obtain paper, markers or color pencils, and draw the information for an element, of your choice. Try to be creative! # protons # neutrons # electrons and valance electrons Mass Phase Symbol Name Group number Period number

Isotopes  Atoms of the same element but different mass number.  Boron-10 ( 10 B) has 5 p and 5 n  Boron-11 ( 11 B) has 5 p and 6 n 10 B 11 B

Two isotopes of sodium.

AVERAGE ATOMIC MASS  Boron is 20% 10 B and 80% 11 B. That is, 11 B is 80 percent abundant on earth.  For boron amu: = [0.20 (10 amu)] + [0.80 (11 amu)] = 10.8 amu 10 B 11 B

Relating to the Periodic Table 13 Al Atomic number Atom symbol AVERAGE Atomic Mass

STOP Isotope Practice Problems

Chapter 4.4 Radioactive Decay

Radioactivity  Atoms decay into other atoms  The rays/particles emitted are called radiation  Three common types of radiation:  Alpha Particles (α)  Beta Particles (β)  Gamma Rays (γ)

Alpha Particles PropertyAlpha CompositionAlpha Particles DescriptionHelium He 4 2 Charge2 Mass6.64 E -24 Penetrating PowerBlocked by paper An alpha particle (α) has the same composition as a helium nucleus—two protons and two neutrons—and is therefore given the symbol

Beta Particles PropertyBeta CompositionBeta Particles DescriptionElectrons 0 -1 β Charge Mass9.11 E -29 kg Penetrating PowerBlocked by foil Very-fast moving electron that has been emitted from an unstable nucleus. Beta particles are represented by the symbol The zero indicates the insignificant mass of an electron

Gamma Rays PropertyGamma CompositionGamma Ray Description Photons 0 0 ϒ Charge0 Mass0 kg Penetrating PowerBlocked by lead Gamma rays are high-energy electromagnetic radiation. They are denoted by the symbol. GR emission doesn’t change atomic mass or atomic number.

Half-Life  Amount of time it takes for one half of a sample of radioactive atoms to decay Amount remaining = (Initial amount)(1/2) n

Half-Life Calculation #1  You have 400 mg of a radioisotope with a half- life of 5 minutes. How much will be left after 30 minutes?

Half-Life Calculation #2  Suppose you have a 100 mg sample of Au-191, which has a half-life of 3.4 hours. How much will remain after 10.2 hours?

Half-Life Calculation # 3  Cobalt-60 is a radioactive isotope used in cancer treatment. Co-60 has a half- life of 5 years. If a hospital starts with a 1000 mg supply, how many mg will need to be purchased after 10 years to replenish the original supply?

Answers to Half-Life Calculations  Half-Life Calculation #1  6.25 mg  Half-Life Calculation #2  12.5 mg  Half-Life Calculation #3  750 mg

THE END TEST THURSDAY Sept. 22