The Fundamental Ideas in Chemistry

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  • Created on: 08-06-14 16:59
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  • The Fundamental Ideas in Chemistry
    • Atoms and Elements
      • All substances are from 100 elements. Elements are made up of one type of atom only. Compounds are made up of two or more different types of atoms chemically bonded together.
      • - All elements are made up of atoms. When two or more atoms join together a molecule is formed. The atoms in elements and compounds are held together by giving, taking or sharing electrons. We say that they are held together by chemical bonds.
      • (aq) aqueous: dissolved in water. Mass doesn't change in a chemical reaction.
      • Inside atoms: Atoms consist of three sub-atomic particles: protons, neutrons and electrons. Protons and neutrons are in the nucleus and electrons are in energy levels/shells.
      • Every element has a chemical symbol, a relative atomic mass (number of protons + number of neutrons) and an atomic proton number (number of protons) E.g. Lithium: Li, relative atomic mass=7, atomic proton number=3.
      • Proton (mass=1, charge= +1), neutron (mass=1, charge= 0) electron (mass= 1/2000, charge= -1). Number of protons=number of electrons
      • Number of electrons in outer shell tells us what group the element is in and the number of energy levels there are in an atom tells us the period (periodic table). Need to know first 20 elements.
      • Electrons-Chemistry. Protons and neutrons-Radioactivity
    • Writing Equations
      • The equations need to be balanced and have the same number of atoms of each side of the equation. Also, the state of the subtance needs to be written next to the substance (e.g. solid (s)). Do not change the small numbers in the chemical formulae.
      • S (g) + O2 (g) ? SO2 (g)
      • 2Mg (s) + O2 (g) ? 2MgO (s)
      • N2 (g) + 2O2 (g) ? 2NO2 (g)
      • Li (s) + Cl2 (g) ? 2LiCl (s)
      • ZnO (s) + H2SO4 (l) ? ZnSO4 (s) + H2O (l)
      • CaCO3 (s) + HCL (aq) ? CaCl2 (aq) + CO2 (g) + H2O (l)
      • Alternative to hydrochloric acid is sulfuric acid Hydrochloric Acid ? Chloride salt Sulfuric Acid ? Sulphate salt. Nitric Acid ? Nitrate salt
    • The Periodic Table
      • There are over 100 different elements in the periodic table. Groups in the periodic table contain elements with similar properties.
      • Atoms of each element are represented by a chemical symbol: Oxygen: O, Sodium: Na, Fluorine: F
      • Elements in the same group have the same number of electrons in the highest energy level (similar chemical properties).
      • Periods show how many energy levels there are
      • Group 8, Noble gases are unreactive because their atoms have a stable arrangement of eletrons (full outer shell)
      • All atoms of a particular element have the same number of protons.
      • Atoms of different elements have different numbers of protons
      • Electron arrangement of: H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca.
    • Electron Configuration
      • H=1 He=2, Li=3, Be=4, B=5
      • C=6, N=7, O=8, F=9, Ne=10
      • Na=11, Mg=12, Al=13, Si=14, P=15
      • S=16, Cl=17, Ar=18,  K=19, Ca=20
    • Chemical Reactions
      • Signs of a chemical reaction: smoke, glow, heat, sublimation (solid-gas), colour change etc
      • Mass of Reactants ? Mass of Products
      • Heating magnesium in air - reactants/magnesium is shiny and silver - Bright, white light, heat - products/white powder.
      • Adding magnesium to dilute hydrochloric acid - reactants/ shiny and silver, colourless liquid - bubbly, fizzy - products/white solution, magnesium disappeared.
      • Heating copper carbonate - reactants, shiny silver solid, green solid - limewater is cloudy/carbon-dioxide produced - Cloudy limewater.
      • Magnesium + Oxygen ? Magnesium Oxide Magnesium + Hydrochloric Acid ? Magnesium Chloride + Hydrogen Copper Carbonate ? Carbon dioxide + Copper Oxide
      • Burning Iron Wool: Iron + Oxygen ?(heat)? Iron oxide. 5.6g + 1.6 ? 7.2g
    • Compounds
      • Sodium and chlorine would combine to create sodium chloride which is less harmful as a compound (ionic bonding). Sodium is a silver coloured element and chlorine is a green gas element.
      • There are three types of chemical bonding: ionic bonding (metals/non-metals), covalent bonding (non-metals/non-metals) and metallic bonding (metals/metals).
      • Inert (unreactive, group 8, noble gases). Noble gases are inert because they have full outer shells and are stable.
      • Ionic Bonding: There is an electrostatic force of attraction between oppositely charged ions (E.g. Na+ and Cl- neutralise each other). Metals always transfer electrons to non-metals. Anion (-). Cation (+)
      • Compounds formed from metals and non-metals consists of ions. These are charged particles formed when electrons transfer from one atom to another. Ions have a stable arrangement of electrons. The forces fo attraction between ions (ionic bonds) act in all directions.
      • Covalent bonds share electrons to form groups of atoms which are held together by covalent bonds are called molecules.
      • When non-metals react, they need to gain electrons to fill their outer shell and become stable. They share electrons with each other and both atoms have a full outer shell. The force of attraction is called a covalent bond. Non-metals joins by a chemical bons and becomes a molecule (can be compound or element, nitrogen, oxygen, hydrogen and the halogens are in pairs).
      • Monoatomic - one atom (Noble gas). Diatomic - two atoms in a molecule
      • Need to be able to show ionic covalent bonds using: displayed formulae, molecular formulae and a dot and cross diagram.(For covalent bonds, outer shells are drawn only)
      • Compounds made from non-metals consists of molecules. The atoms are held together by shared pairs of electrons and are called covalent bonds.


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