SBI4U Chemistry Fundamentals: Part 1

IsotopesIsotopes are atoms of the same element but have different numbers of neutrons. Isotopes X A Z Mass number, number of protons AND neutrons Element Symbol (i.e. Au) Atomic Number, number of protons So, how do we calculate the number of neutrons?For a given element, which part never changes?

Bonding There are two types of bonds: Chemical and Physical

Depend on valence of electrons (refer to page 12) Periodic table is grouped according to valence number Types of chemical bonds: ionic or covalent Type of chemical bond depends on character of the elements involved Ionic = positively charged metal + negatively charged non-metalIonic Covalent = neutral non-metal + neutral non-metalCovalent Chemical Bonds

Electronegativity & Polarity Electronegativity is a measure of an atom's attraction for electrons in the covalent bond If an element has a high electronegativity, it will pull electrons closer to its nucleus Since electrons are negatively charged, the atom attains a partial negative charge This results in a polar bond so that the electrons are shared unequally

Covalent bonds can be broken down into two types: Polar bonds Non-polar bonds Polarity depends on the electronegativities of the two atoms involved in the chemical bond (refer to page 14) If there is no difference in electronegativity, the covalent bond is considered nonpolar

If the difference in electronegativity is between 0 and 1.7, the covalent bond is polar Fluorine and Oxygen have very high electronegativities but oxygen is the most Biologically significant since it is much more plentiful than fluorine Electronegativity & Polarity

Physical Bonds Physical bonds form BETWEEN MOLECULES (chemical bonds form between atoms) There are three types of physical bonds: London dispersion forces (weakest) Dipole-Dipole forces Hydrogen bonds (strongest) Please read p17 and make notes on these three types Hydrogen bonds occur amongst polar molecules van der Waals forces

ChemicalPhysical Type of Bonds Inter or Intramolecular Strength Summary Ionic or Covalent London dispersion forces, dipole-dipole forces, and hydrogen bonds IntramolecularIntermolecular StrongestGenerally Weaker

Redox Reactions. Oxidation Reduction

Oxidation Numbers The oxidation number of an atom in an element is zero. E.g. Mg in Mg, O in O 2.

Oxidation Numbers The oxidation numbers of atoms in a compound add up to zero. F O-2 H+1 Cl Oxidation state of Mg in MgCl 2 ? +2

Oxidation Numbers The oxidation numbers of atoms in a compound add up to zero. F O-2 H+1 Cl Oxidation state of N in NH 3 ? -3

LEO GER Oxidation: Gain of oxygen Loss of electrons Reduction: Loss of oxygen Gain of electrons Increase in oxidation number Decrease in oxidation number

Which one is oxidized? Reduced?

But in Biology… Oxidation: Loss of Hydrogen atoms Reduction: Gain of Hydrogen atoms

Homework Do “Are you Ready” p. 4-5 Read p (skip hybridization) What are radioisotopes? How can they be used in the medical field? (use page 8-9) Make notes on types of bonds – intramolecular and intermolecular *polarity & electronegativity – how are they related? Do #15-16 on p. 23