Physical science 4.2 : The Atom

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  • 1. The Atom
    Physical Science
    Chapter 4.2
  • 2. Objectives:
    Describe the size of an atom
    Namethe parts of an atom
    Describe the relationship between numbers of protons and neutrons and atomic number
    State how isotopes differ
    Calculate atomic masses
    Describe the forces within an atom
    Bellringer
    An atom is the smallest particle into which an element can be divided and still be that element. Now that scientists have learned that an atom is made up of even smaller particles, is this definition still accurate?
  • 3. How small is an atom?
    Three One-Hundred-Millionths of a Centimeter!
    Scientists know that aluminum is made of average-sized atoms. An aluminum atom has a diameter of about 0.00000003 cm
  • 4. What is an atom made of?
    The Nucleus
    Protons
    Positively charged particles in the nucleus
    Neutrons
    Particles of the nucleus that have no electrical charge
    Outside the Nucleus
    Electrons
    Negatively charged particles in atoms
    Found around the nucleus within electron clouds
  • 5.
  • 6. How do atoms of different elements differ?
    Starting Simply
    The hydrogen atom has one proton and one electron
    Now for Some Neutrons
    The helium atom has two protons, two neutrons, and two electrons
  • 7. Building Bigger Atoms
    For bigger atoms
    simply add protons, neutrons, and electrons
    Protons and Atomic Number
    Atomic number
    The number of protons in the nucleus of an atom
    All atoms of an element have the same atomic number
  • 8. Isotope
    Atoms that have the same number of protons but have different numbers of neutrons
  • 9. Properties of Isotopes
    An unstable atom is an atom with a nucleus that will change over time
    Radioactive isotope
    Telling Isotopes Apart
    You can identify each isotope of an element by its mass number
    Mass number
    Sum of the protons and neutrons in an atom
  • 10.
  • 11. Naming Isotopes
    To identify a specific isotope of an element
    write the name of the element followed by a hyphen and the mass number of the isotope
    Carbon-12
    6 protons, 6 neutrons
    Chlorine isotope has 17 protons and 18 neutrons
    SOchlorine-35,
    Mass number = protons + neutrons
    = 17 + 18 = 35
    Calculating the Mass of an Element
    Atomic massof an element
    weighted average of the masses of all the naturally occurring isotopes of that element
  • 12.
  • 13. Forces in the atom
    Four Basic Forces
    Four basic forces are at work everywhere
    even within the atom
    These forces are:
    gravitational force
    electromagnetic force
    strong force
    weak force
    These forces work together to give an atom its structure and properties