Covalent Bonding

• What is the main characteristic of covalent bonding?


  Atoms share electrons to achieve full outer shells
• What do non-metal atoms do when they bond together?


  They share pairs of electrons
• How are covalent bonds formed between atoms?


  The positively charged nuclei are attracted to the shared pair of electrons
• In which energy levels do atoms share electrons during covalent bonding?


  In their outer shells
• What does each single covalent bond provide for each atom?


  One extra shared electron
• Why do atoms generally make enough covalent bonds to fill their outer shell?


  To achieve the electronic structure of a noble gas
• In what types of compounds does covalent bonding occur?


  Compounds of non-metals
• Give an example of a compound that exhibits covalent bonding.


  Water (H₂O)
• What is a dot and cross diagram used for?

  To show the bonding in covalent compounds
• How many outer electrons does nitrogen have?


  Five outer electrons
• What do the electrons drawn in the circles between the outer orbitals represent in dot and cross diagrams?


  Electrons shared between the atoms
• What are the limitations of dot and cross diagrams?


  They do not show the relative sizes of atoms or their spatial arrangement
• What does the displayed formula of ammonia (NH₃) show?


  The covalent bonds as single lines between atoms
• What is a limitation of the displayed formula in showing molecular structure?

  It does not show the 3D structure of the molecule
• What does a 3D model of ammonia illustrate?


  The atoms, covalent bonds, and their arrangement in space
• What is a drawback of using 3D models for large molecules?


  They can become confusing with many atoms
• How can you find the molecular formula of a simple molecular compound?


  By counting the number of atoms of each element in the diagrams
• What is the molecular formula of ethane if it has two carbon atoms and six hydrogen atoms?


  C₂H₆
• What are the different ways to represent covalent bonds?


  • Dot and cross diagrams
  • Displayed formulas
  • 3D models
• What are the strengths and weaknesses of different representations of covalent bonds?

  Strengths:

  • Dot and cross diagrams show electron origin
  • Displayed formulas show connections between atoms
  • 3D models show spatial arrangement

  
  

  Weaknesses:

  • Dot and cross diagrams do not show size or arrangement
  • Displayed formulas do not show 3D structure
  • 3D models can be confusing for large molecules
• What does a molecular formula represent in a substance?


  It shows the number of atoms of each element present in a compound or molecule.
• What is an example of a molecular formula?


  An example is $C_2H_4O_2$.
• What is an empirical formula?


  It is the simplest, whole number ratio of atoms of each element in a compound.
• What is an example of an empirical formula?


  An example is $CH_2O$.
• What is the ratio of carbon to hydrogen to oxygen in the empirical formula $CH_2O$?


  The ratio is 1:2:1.
• What is a covalent bond?


  A covalent bond is a shared pair of electrons between atoms.
• What are some uses of covalent bonding?


  It is used to make polymers and giant covalent structures.
• What do dot structures represent in covalent bonding?


  They show the arrangement of electrons in bonds but not the relative sizes of atoms.
• What is a limitation of displayed formulas in representing molecules?

  They do not show the 3D shape of the molecule.
• What is the molecular formula for water?


  The molecular formula for water is $H_2O$.
• What is the molecular formula for methane?


  The molecular formula for methane is $CH_4$.
• What is the molecular formula for ammonia?


  The molecular formula for ammonia is $NH_3$.
• What are the types of substances that have covalent bonds?


  • Simple molecular substances (e.g., chlorine, ammonia)
  • Strong covalent bonds within molecules
  • Weak intermolecular forces between individual molecules
• What is the nature of the forces between individual molecules in covalent compounds?


  There are weak intermolecular forces that are easily broken.
• What type of bonds are covalent bonds?


  Very strong bonds
• Why is a lot of energy required to break covalent bonds?


  Because covalent bonds are very strong
• What should not be broken in covalent structures?

  Covalent bonds
• What type of forces are broken when substances melt or boil?

  Intermolecular forces
• What is the state of substances with low melting and boiling points at room temperature?


  They are mostly gases or liquids
• At what temperature does chlorine boil?


  • 34°C