Mrs. Jackson Third Block

Standard PS.2 The student will demonstrate an understanding of the structure and properties of atoms.

Structure of the Atom An element is matter that is composed of one type of atom, which is the smallest piece of matter that still retains the property of that element. Atoms are composed of three subatomic properties: Protons Electrons neutrons

Cont… Protons have a positive charge and are found in the nucleus of the atom. Neutrons have no charge and are also found in the nucleus of the atom. Electrons have a negative charge and are moving in space outside the nucleus. The positively charged center of the atom Is called the nucleus.

Cont… Protons and neutrons are composed of smaller particles called quarks. Scientist theorize that an arrangement of three quarks held together by a strong nuclear force produces a proton. The electron cloud is the area around the nucleus where its electrons are most likely found. (100,000 times larger than the diameter of the nucleus)

Isotopes Atoms of the same element that have different numbers of neutrons are called isotopes. Example Carbon-12, carbon- 13, and carbon- 14 Living organisms on Earth contain carbon. Carbon -12 makes up 99% of this carbon. Carbon-13 & carbon-14 make up the other 1%. Which isotopes are archaeologists most interested in?

Answer Archaeologists are most interested in carbon-13 and carbon-14 because these isotopes are radioactive. The longer a once living organism has been dead, the less radioactive it will be per gram of carbon. This gives archaeologists a way to determine the approximate age of once living organisms.

Periodic Table In the late 1800’s, Dmitri Mendeleev searched for a way to organize elements. Mendeleev arranged the elements by increasing atomic masses. Henry Mosley revised Mendeleev’s table and arranged the elements by increasing atomic number. Today the periodic table is arranged by increasing atomic number and by physical and chemical properties.

Mendeleev’s periodic table

Electron Cloud Structure Electrons within an electron cloud have different amounts of energy. The energy levels nearer the nucleus have lower energy than those levels far away. An electron dot diagram uses the symbol of the element and dots to represent the electron in the outer energy level.

Radioactivity Strong force- causes protons and neutrons to be attracted to each other. The process of nuclear decay is called radioactivity. All nuclei that contain 83 protons or more are radioactive. Almost all elements with 92 or more protons do not exist naturally on Earth.

Nuclear Decay Three types of nuclear decay Alpha particles Beta particles Gamma radiation Alpha particle Made of two protons and two neutrons Same as the nucleus of helium

Cont… Beta particles A neutron decays into a proton and emits an electron Gamma radiation Most penetrating form of nuclear radiation Electromagnetic rays with highest frequency and shortest wave length Have no mass or charge and travel at the speed of light.

Cont…. Half life- a measure of the time required by the nuclei of an isotope to decay. Carbon dating- Carbon-14 is often used to estimate the age of plant and animal remains. Half life of 5,730 years Uranium dating Used to estimate the age of rocks

Nuclear Fission The process of splitting a nucleus into several smaller nuclei is called nuclear fission. The series of repeated fission reactions caused by the release of neutrons in each reaction is a chain reaction. The critical mass is the amount of material required so that each fission reaction produces approximately one more fission reaction.

Nuclear Fission

Nuclear Fusion When two nuclei with low masses are combined to form one nucleus of larger mass it is called nuclear fusion. Ex) Sun

Fusion

Nuclear Medicine Tracer When a radioisotope is used to find or keep track of molecules in an organism. Cobalt-60 used in treating cancerous tumors Drawbacks Healthy tissues are damaged in the treatment of cancer. Storage of nuclear materials

Nuclear Weapons Some fission and fusion nuclear reactions can be used in weapons. Benefits Some people believe that nuclear weapons are a deterrent to war. Possible drawbacks Specialized technology is required to refine the fuel and to produce the weapons.

Drawbacks cont… Tremendous amounts of energy available from small amounts of fuel so smuggling is possible. The potential for a tremendous amount of destruction, both material and biological.

Nuclear Power Reactors Energy from controlled nuclear fission is used to heat water into steam, The steam expands turning a turbine which spins a huge magnet within a coil of metal wire. The moving magnetic field forces electrons to flow in the metal wire. The primary difference between a coal-powered electric generating plant and a nuclear-powered electric generating plant is the method of heating water;

Cont… Benefits Tremendous amounts of energy available from small amounts of fuel No greenhouse gas or other air pollution from the burning of fossil fuels Can be used anywhere Abundance of fuel Non-reliance on fossil fuel

Drawbacks Requires specialized technology to refine the fuel. Can cause thermal pollution to water systems Exposure of workers in nuclear facilities to radiation.