Science Module 8th Grade
TAKS Objective 3 The student will demonstrate an understanding of the structure and properties of matter.
TEKS 8.8 A and B The student knows that matter is composed of atoms. The student is expected to: • describe the structure and parts of an atom; and • identify the properties of an atom including mass and electrical charge.
Objectives • The learner will be able to describe the parts of an atom. • The learner will be able to compare mass and charges of the electron, proton, and neutron.
Lesson Objectives “Continued” • The learner will use appropriate models and analogies to describe the size of an atom and its particles. • The learner will explain the development of the atomic theory.
Misconceptions True or False Electrons are little spheres that orbit the nucleus of an atom
Electrons have no known shape and almost no mass. They do not orbit; they move randomly in an electron cloud.
True or False Atoms are like miniature solar systems
The only thing an atom and the solar system have in common, is both are mostly empty space.
True or False The electron is the same size as a proton or neutron
The electron has no size and practically no mass compared to a proton or a neutron.
Development of Atomic Theory 440 BC - Democritus first suggested the existence of atoms
1803 - John Dalton suggested a 3-part atomic theory (1) everything is made of atoms (2) atoms combine to make new substances (3) atoms of the same element are alike
1897 – J.J. Thomson proposed the plum pudding model of the atom. Atoms are mostly positive with negative particles.
1909 – Rutherford conducted his famous gold foil experiment discovering that atoms were mostly empty space with a dense positive center.
1913 – Bohr describes the orbit of atoms as traveling around the nucleus in definite orbits (planetary model).
1914 – Moseley used the cathode rays to determine the number of positive charges in the nucleus (first concept of atomic number).
1926 – Schrodinger developed quantum theory to describe the behavior of subatomic particles.
TEGS: The Atom Quantum Atom
1 2 3 4 Engage Cut a piece of paper in half as many times as you can. Paper Cutting Link
Explore The “Black” box activity is important on several levels: • Students explore studying things they cannot see or directly touch. • Students share information with others to expand and check results. • Students learn that scientists cannot check for the right answer (Keep the box closed and never reveal what is inside!)
Explore Who knew? is an activity designed to help students understand how science is built upon the investigations of previous scientists and determined in large part by the technology available.
Explain The atom is composed of mostly empty space. Atom Field video http://www.tcet.unt.edu/tegs/chapter3/Atomic%20field_Medium.mov
This animation shows the Scanning Tunneling Microscope (STM) mapping atomic clouds in the silicon material. The STM uses a needle with a single atom on the tip to “see” the silicon atoms by their charged electron clouds. STM Animation http://www.tcet.unt.edu/tegs/chapter3/STM%20Animation.ppt
Electrons are very small compared to a proton. If the proton were the mass of an automobile, the electron would have the mass of a bag of potato chips.
Elaborate • Particle Play • Stripping Electrons • On the Shoulders of Giants
Evaluate Allow students to choose a particle and write an illustrated “biography.” Include the particle’s discovery, charge, and location in the atom.