Drawing dot and cross diagrams

• What is a covalent bond?

  A covalent bond is a shared pair of electrons.
• What do covalent bonding forms?

  Covalent bonding forms molecules.
• What are the properties of substances with small molecules?

  They have low melting and boiling points, and do not conduct electricity.
• What is the relationship between the number of covalent bonds an atom can form and its outer shell of electrons?

  • The number of covalent bonds an atom can form is equal to the number of electrons needed to achieve a full outer shell.
  • For most elements, a full outer shell is eight electrons.
• How many covalent bonds can Carbon (C) form?

  Carbon can form 4 covalent bonds.
• How many covalent bonds can Nitrogen (N) form?

  Nitrogen can form 3 covalent bonds.
• How many covalent bonds can Oxygen (O) form?

  Oxygen can form 2 covalent bonds.
• How many covalent bonds can Chlorine (Cl) form?

  Chlorine can form 1 covalent bond.
• How many covalent bonds do hydrogen atoms form?

  Hydrogen atoms form one covalent bond.
• How do you draw a dot and cross diagram for a molecular substance?

  1. Identify the formula of the substance.
  2. Draw circles for each atom.
  3. Label the circles with the respective atom symbols.
  4. Overlap circles to represent shared electrons.
  5. Add non-bonding outer electrons.
• What is the formula for ammonia?

  The formula for ammonia is NH₃.
• How many circles should you draw for the ammonia molecule?

  You should draw four circles for ammonia (1 N and 3 H).
• How should the circles in a dot and cross diagram be arranged?

  It is often easiest to draw circles at 90° or 180° to each other.
• What does a complete dot and cross diagram for ammonia show?

  A complete dot and cross diagram for ammonia shows bonding pairs and non-bonding outer electrons.
• How do you draw a dot and cross diagram for methane, CH₄?

  Draw one C circle and four H circles overlapping with shared spaces.
• What are the key components of a dot and cross diagram?

  • Atoms represented by circles
  • Shared electrons shown as overlapping circles
  • Non-bonding electrons shown outside the overlapping area
• What is the definition of a molecular substance?

  A molecular substance is made up of small groups of atoms held together by covalent bonds.
• What is the definition of an element?

  An element is a substance made of one type of atom only.
• What is the definition of a formula in chemistry?

  A formula is a combination of symbols that indicates the chemical composition of a substance.
• What are the groups in the periodic table?

  • Groups are vertical columns in the periodic table.
  • They contain elements with similar chemical properties.