Chemistry: Atoms and Limestone

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  • Created by: brunette
  • Created on: 16-03-14 18:43
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  • Chemistry
    • Atoms
      • Protons, Neutrons and Electrons.
        • Protons are positively charged particles found within atomic nuclei.
        • Electrons are the negatively charged particles of atom.
        • Neutrons are the particles in an atom that have a neutral charge.
      • Nucleus
        • The nucleus is the very dense region consisting of protons and neutrons at the center of an atom.
      • The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons.
      • All substances are made from tiny particles called atoms. An atom has a small central nucleus made up of smaller sub-atomic particles called protons and neutrons. The nucleus is surrounded by even smaller sub-atomic particles called electrons.
      • Atomic Number
        • The atomic number of an atom is the number of protons it contains.
      • Mass Number
        • The mass number of an atom is the total number of protons and neutrons it contains. The mass number of an atom is never smaller than the atomic number. It can be the same, but is usually bigger.
      • Electronic structure
        • The electrons in an atom occupy energy levels. These are also called shells. Each electron in an atom is found in a particular energy level. The lowest energy level (innermost shell) fills with electrons first.
        • Each energy level can only hold a certain number of electrons before it becomes full. The first energy level can hold a maximum of two electrons, the second energy level a maximum of eight, and so on.
    • Limestone
      • Limestone is mainly calcium carbonate, CaCO3, which when heated breaks down to form calcium oxide and carbon dioxide.
      • Calcium oxide reacts with water to produce calcium hydroxide. Limestone and its products have many uses, including being used to make cement, mortar and concrete.
      • Thermal deomposition
        • Calcium carbonate breaks down when heated strongly. This reaction is called thermal decomposition.
        • Metals high up in the reactivity series (such as sodium, calcium and magnesium) have carbonates that need a lot of energy to dec ompose them. Indeed, not all the carbonates of group 1 metals decompose at the temperatures reached by a Bunsen burner.
        • Metals low down in the reactivity series, such as copper, have carbonates that are easily decomposed.
      • Uses of limestone
        • Carbonates react with acids to produce carbon dioxide, a salt and water.
        • Since limestone is mostly calcium carbonate, it is damaged by acid rain
        • When limestone is heated strongly, the calcium carbonate it contains decomposes to form calcium oxide.

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