fundamental ideas of chemistry

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  • Fundamental Ideas in Chemistry
    • All substances are made of atoms
      • A substance that is made of only one sort of atom is called an element
        • there are about 100 different elements
          • elements are shown in the periodic table
            • the groups contain elements w similar properties
    • atoms of each element are represented by a chemical symbol
    • atoms ahve a small central nucleus, which is made up of protons & neutrons, w electrons around it
    • protons, neutrons & electrons have different electrical charges; proton has +1, neutron has; 0 and electron; -1
    • In an atom, the number of electrons is equal to the number of protons in the nucleus.
      • atoms have no overall electrical charge
    • all atoms of a particular element have the same number of protons
      • atoms of different elements have different numbers of protons
    • the number of protons in an atom of an element is its atomic number
      • the sum of the protons & neutrons in an atom is its mass number
    • electrons occupy particular energy levers
      • each electron in an atom is at a particular energy level.
        • the electrons in an atom occupy the lowest available energy levels
    • elements in the same group in the periodic table have the same number of electrons in their highest energy level & this gives them similar chemical properties
      • the elements in group 0 are called the noble gases
        • noble gases are unreactive because their atoms have stable arrangements of electrons
    • when elements react, their atoms join with other atoms to form compounds.
      • this involves giving, taking or sharing electrons to form ions or molecules
        • compounds formed from metals & non - metals consists of ions
          • compounds formed from non-metals consist of molecules. in molecules atoms are held together by covalent bonds


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