Interactive Periodic Table!!

http://www.scientificamerican.com/article/chemistry-the-elements-revealed-interactive-periodic-table/

Balancing Chemical Equation

1.   Visit the website http://funbasedlearning.com/chemistry/chemBalancer/default.htm

     This website focuses on Balancing Equation.

2.    Before playing the game, click on “Directions” for instructions.

3.    Please click on “Start Game” to begin. Fill in the blanks with appropriate numbers. The number “1” needs to be typed into the blank for you to proceed to another question.

Chemical Bonding Answers

Section B: Structured Questions

1(a)

Note: - Electrons shared must be drawn in the empty space and NOT on the lines.
         - Remember to count the number of electrons that each atom originally have. (Nitrogen should               have 5 cross)

(b)
There are three single bonds and one double bond between the phosporus and oxygen atoms in phosporic acid.
Each bond is formed by the sharing of two electrons.
Thus, the total number of electrons shared between the phosporus and oxygen atoms is 5x2=10.


2(a)(i) BeCl2
     (ii) SiCl4

  (b) They have a stable octet electronic configuration and thus do not form compounds.
  (c)(i) A lithium atom loses an electron to as chlorine atom. The lithium and chloride ions formed are            held together by ionic bonds.

     (ii) A chlorine atom shares a pair of electrons with a fluorine atom to form a single covalent bond.

  (d) In NaCl, the Na⁺ and Cl^- ions are arranged in a giant lattice structure and the oppositely charged        ions are held together by strong forces of attraction.

       A large amount of energy is needed to break the strong ionic bonds in NaCl.

       In CCl₄, the CCl₄ molecules are held together loosely by weak intermolecular forces.

       These intermolecular forces can be easily overcome.

      Thus, NaCl has a much higher boiling point than CCl₄.

Section C: Free-Response Questions

1(a)(i) Each Mg2+ ion is surrounded by six O^2- ions and vice versa. The overall ratio of Mg²⁺ ions to           O^2- ions is 1:1. Thus, the chemical formula of magnesium oxide is MgO.

      (ii) 

  (b) The bulb lights up, showing that aqueous sodium chloride conducts electricity. This is because            the sodium and chloride ions are free to move about in aqueous solution.

2(a)

 (b) Silicon dioxide has a giant molecular structure. The silicon and oxygen atoms are held together by       strong covalent bonds. A large amount of energy is required to break these strong bonds.

      Hence, silicon dioxide exists as simple molecules, which are held together by weak intermolecular       forces. These forces are easily overcome. Hence carbon dioxide has low melting and boiling 

      points and exists as a gas at room temperature.

 (c) All the outer electrons of the silicon and oxygen atoms in silicon dioxide are used for bonding.           There are therefore no free electrons that move through the structure. Hence, silicon dioxide does       not conduct electricity.

3(a) Diamond forms a three-dimensional structure in which each carbon atom is covalently bonded to          four other carbon atoms, which are in turn bonded to four more carbon atoms.
      These covalent bonds are very strong and difficult to break. Thus, diamond is hard.
      Graphite is made up of layers of carbon atoms which are held loosely by weak intermolecular             forces of attraction. These layers of carbon atoms slide over each other easily when a force is  
      applied. Thus, graphite is soft and slippery.

 (b) Graphite is made up of layers of carbon atoms. Each carbon atom has one outer electron that is           not used for bonding. These electrons move freely along the layers from one carbon atom to the         next (delocalised electrons), allowing graphite to conduct electricity.
      In diamond, all the outer electrons of the carbon atoms are used to form covalent bonds. There are       no free electrons that move through its structure. Thus, a diamond does not conduct electricity.