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Unit 3-1 notes page 2-28 Properties of Atoms and the Periodic Table Notes
Section 1:
Atom = the smallest piece of matter that still retains the properties of an element
Nucleus = the small, positively charged center of an atom
Protons = particles with an electrical charge of +1found in the nucleus.
Neutrons =neutral particles that do not have an electrical charge and is found in the nucleus.
Electrons = particles with an electrical charge of -1 found in the electron cloud.
Quarks = smaller particles that make up protons and neutrons
Electron Cloud = the area around the nucleus of an atom where its electrons are most likely to be found
Atomic Number = The number of protons in an atom
Mass Number =(Atomic Mass)The sum of the number of protons and number of neutrons in the nucleus of an atom
(mass of electrons is negligible; ex. ticks on a dog
Isotopes = Atoms of the same element that have different numbers of neutrons
Average Atomic Mass =The weighted-average mass of the mixture of its isotopes
Periodic Table =The elements are arranged by increasing atomic number and by changes in physical and chemical properties
Groups (Families) =The vertical columns in the periodic table that are numbered 1 through 18
Electron dot diagram=(Lewis Structure)The element symbol surrounded by the valence electrons.
*Valence electrons=Electrons located in the outermost energy level.
Periods =The horizontal rows on the periodic table
*Energy Levels =Shells surrounding the nucleus containing electrons
–(Atomic Mass)- the total number of protons and neutrons in the atomic nucleus of an atom.
History of the atom/Atomic models
A) Democritus and Aristotle:
Both believed that the atom was indivisible-It could not be broken down further.
B) Plum pudding model:
J.J. Thomson or Lord Kelvin: Suggested that the atom was a positive cloud with randomly spaced electrons. (Chocolate chip cookie)
C) Rutherford model:
Earnest Rutherford: The center of the atom is positively charged mass surrounded by electrons randomly spaced.(Mosquitoes around a light.)
D) Bohr Model:
The center of the atom is positively charged mass surrounded by electrons in definite energy levels.(Rungs on a ladder. Or Bullseye.)
E) Modern Atomic Model: The center of the atom is positively charged mass surrounded by electrons found in specific shells. (Think-cars on a highway.)
Three divisions of the periodic table.
Metals – an element that gives up electrons relatively easily and is typically lustrous, malleable, and a good conductor of heat and electricity.
Nonmetals – an element that does not exhibit metallic characteristics. Chemically, a typical nonmetal accepts electrons from a metal.
Metalloids or Semimetals – an element that has both metallic and non- metallic properties.
Metals usually possess the following characteristics:
Malleable: Able to be pounded into various shapes and NOT lose strength.
Ductility: Able to be drawn into a wire.
Luster: Reflect light/ shiny appearance.
Conductor: Able to transmit electricity and heat very readily.
Reactivity: Produce hydrogen gas when mixed with acids
Nonmetals usually poses the following characteristics:
Brittle: Break when hit with a hammer.
Dull: Most do NOT reflect light appear shiny.
No ductility: Can NOT be drawn into a wire.
Nonconductor: Do NOT transmit heat or electricity.
Reactivity: Do NOT react with acid to form Hydrogen.
Three main particles of the atom.
PARTICLE
LOCATION
CHARGE
MASS
PROTON
Nucleus
+1
1 AMU
ELECTRON
e- Cloud
-1
0 AMU
NEUTRON
Nucleus
0
1 AMU
Random motion- movement in all directions and at different speeds.
Diffusion- The movement of particles from an area of higher concentration to an area of lower concentration
Kinetic energy- Added energy increased of the particles increased.
Thermodynamics- the study of heat.
Thermal expansion- The increase in volume of a material when motion increases.
Thermal contraction- when particle motion decreases and causes the particles to occupy less volume.
Temperature- The measure of the average kinetic energy of particles in a material.
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