Exam Review - Biology

• How many electrons are in a single covalent bond?

  2 electrons
•  WHAT IS A VALENCE ELECTRON?

  An electron in the outermost energy level of an atom.
• WHICH TYPE OF DIAGRAM SHOWS: THE CONTENTS OF THE NUCLEUS OF AN ATOM

  BOHR-RUTHERFORD
• WHICH TYPE OF DIAGRAM SHOWS: THE NUMBER OF VALENCE ELECTRONS ONLY

  ELECTRON DOT
• WHICH TYPE OF DIAGRAM SHOWS: THE SHAPE AND TYPE OF BONDS IN A MOLECULE

  Lewis structure diagram
• WHICH TYPE OF DIAGRAM SHOWS: THE ARRANGEMENT OF ELECTRONS IN AN ATOM

  Electron shell diagram
• WHAT IS THE COMBINING CAPACITY FOR:

  HYDROGEN: 1

  CARBON: 4 

  OXYGEN: 2

  NITROGEN: 3
• HOW MANY BONDS CAN THEY MAKE?

  HYDROGEN: 1

  CARBON: 4

  OXYGEN: 2

  NITROGEN: 3
• Whet is an asymmetrical molecule?

  A molecule that does not have identical atoms or groups on each side.
• What are functional groups?

  Functional groups are specific groups of atoms within a molecule that determine its chemical properties and reactivity.
• Hydroxyl

  • Chemical formula: -OH
  • Structural formula: -OH
  • Found in: alcohols
• Carboxyl

  • Chemical formula: -COOH
  • Found in: acids
  • Structural formula:

  
• Molecular Polarity and Intermolecular Forces are topics in Biochemistry.
• Functional groups are groups of atoms in a compound that determine the chemical behaviour of the compound.
• The same functional group will undergo the same or similar chemical reaction(s) regardless of the size of the molecule it is a part of.
• Polar molecules can dissolve ions of either charge.
• Functional groups are covalent groups of ions that are either strongly polar or ionic.
• Hydrophobic molecules will not dissolve or mix with water.
• Oils, gasoline are examples of non-polar molecules.
• A hydration shell of water molecules keeps ions from re-associating.
• Water orients differently around the cation and anion in a hydration shell.
• Functional groups make hydrocarbons more reactive because they attract other molecules and make them hydrophilic.
• Functional groups are less symmetrical and polar.
• Intermolecular forces are interactions within molecules.
• Unequal sharing of the electrons can occur within molecules.
• Electronegativity is how strongly the atom holds onto electrons.
• The difference between the electronegativity of the atoms in a bond is known as Δ EN.
• A polar bond is one where unequal sharing of the electrons occurs, for example, between O-H, C-O ( Δ EN > 0.4).
• A non-polar bond is one where unequal sharing of the electrons does not occur, for example, C-C ( Δ EN = O) or C-H ( Δ EN < 0.4).
• The polarity and molecular shape of a bond depend on the bond polarity and molecular shape.
• Molecular polarity is determined by the presence of polar bonds and asymmetry.
• Polar molecules have at least one polar bond and are asymmetrical.
• Hydrophobic substances either love water or hate it, hydrophilic molecules dissolve in water, like dissolves like.
• Hydrogen bonds are the strongest of intermolecular forces, especially strong dipole-dipole forces, between H+ and N-, O- or F- atoms of a neighbouring polar molecules, and play a vital role in biological systems.
• Water is a polar molecule that clings to itself (cohesion) and other polar molecules (adhesion) due to water molecules forming hydrogen bonds.
• London dispersion forces are especially important for non-polar molecules as it is the only Van der Waals force applicable for these molecules, caused by temporary unequal distribution of electrons, and are very weak attraction between all molecules, the larger the molecule the stronger the attraction.
• Intermolecular forces (IMF) are the force of attraction between two molecules, also known as Van der Waals forces.
• Non-polar molecules have only non-polar bonds or are symmetrical.
• Dipole-dipole forces are stronger than London dispersion forces and hold polar molecules together.
• Carbon (black) has a molar mass of 2.5, Hydrogen (yellow) has a molar mass of 2.1, Oxygen (red) has a molar mass of 3.5.