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Pwpt chemistrycin

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Transcript

  • 1. CHEMISTRY
  • 2. Composition of Matter
    • Matter - Everything in universe is composed of matter
      • Matter is anything that occupies space or has mass
        • Mass – quantity of matter an object has
        • Weight – pull of gravity on an object
  • 3. Elements
    • Pure substances that cannot be broken down chemically into simpler kinds of matter
    • More than 100 elements (92 naturally occurring)
  • 4.
    • 90% of the mass of an organism is composed of 4 elements (oxygen, carbon, hydrogen and nitrogen)
    • Each element unique chemical symbol
      • Consists of 1-2 letters
      • First letter is always capitalized
  • 5. Atoms
    • The simplest particle of an element that retains all the properties of that element
    • Properties of atoms determine the structure and properties of the matter they compose
    • Our understanding of the structure of atoms based on scientific models, not observation
  • 6. The Nucleus
    • Central core
    • Consists of positive charged protons and neutral neutrons
    • Positively charged
    • Contains most of the mass of the atom
  • 7. The Protons
    • All atoms of a given element have the same number of protons
    • Number of protons called the atomic number
    • Number of protons balanced by an equal number of negatively charged electrons
  • 8. The Neutrons
    • The number varies slightly among atoms of the same element
    • Different number of neutrons produces isotopes of the same element
  • 9. Atomic Mass
    • Protons & neutrons are found in the nucleus of an atom
    • Protons and neutrons each have a mass of 1 amu (atomic mass unit)
    • The atomic mass of an atom is found by adding the number of protons & neutrons in an atom
  • 10. The Electrons
    • Negatively charged high energy particles with little or no mass
    • Travel at very high speeds at various distances (energy levels) from the nucleus
  • 11.
      • Electrons in the same energy level are approximately the same distance from the nucleus
      • Outer energy levels have more energy than inner levels
      • Each level holds only a certain number of electrons
  • 12. Energy Levels
    • Atoms have 7 energy levels
    • The levels are K (closest to the nucleus), L, M, N, O, P, Q (furthest from the nucleus)
    • The K level can only hold 2 electrons
    • Levels L – Q can hold 8 electrons
  • 13. Atomic Bohr Model
    • Draw a model of the element lithium.
    • Draw a model of the element carbon.
  • 14. Periodic Table
    • Elements are arranged by their atomic number on the Periodic Table
    • The horizontal rows are called Periods & tell the number of energy levels
    • Vertical groups are called Families & tell the outermost number of electrons
  • 15.  
  • 16. Compounds
    • Most elements do not exist by themselves
    • Readily combine with other elements in a predictable fashion
  • 17.
    • A compound is a pure substance made up of atoms of two or more elements
      • The proportion of atoms are always fixed
    • Chemical formula shows the kind and proportion of atoms of each element that occurs in a particular compound
  • 18.
    • Molecules are the simplest part of a substance that retains all of the properties of the substance and exists in a free state
    • Some molecules are large and complex
  • 19. Chemical Formulas
    • Subscript after a symbol tell the number of atoms of each element
    • H 2 0 has 2 atoms of hydrogen & 1 atom of oxygen
    • Coefficients before a formula tell the number of molecules
    • 3O 2 represents 3 molecules of oxygen or (3x2) or 6 atoms of oxygen
  • 20.
    • The physical and chemical properties of a compound differ from the physical and chemical properties of the individual elements that compose it
  • 21.
    • The tendency of elements to combine and form compounds depends on the number and arrangement of electrons in their outermost energy level
    • Atoms are most stable when their outer most energy level is filled
  • 22.
    • Most atoms are not stable in their natural state
    • Tend to react (combine) with other atoms in order to become more stable (undergo chemical reactions)
    • In chemical reactions bonds are broken; atoms rearranged and new chemical bonds are formed that store energy
  • 23. Covalent Bonds
    • Formed when two atoms share one or more pairs of electrons
  • 24. Ionic Bonds
    • Some atoms become stable by losing or gaining electrons
    • Atoms that lose electrons are called positive ions
  • 25.
    • Atoms that gain electrons are called negative ions
    • Because positive and negative electrical charges attract each other ionic bonds form