Physical Science – Chapter 22 Study Guide Answers
MAKE SURE YOU HAVE YOUR PERIODIC TABLE
AND YOUR SHEET OF POLYATOMIC IONS
Chapter Objectives
1. Describe how a compound differs from its component elements.
Elements often have extremely different physical and chemical
properties than the compounds they create
Example: NaCl – crystals, edible, white
Na – solid, silvery, shiny, reacts violently with water
Cl2 – poisonous, yellow, gas
2. Explain what a chemical formula represents
Tells which elements are in the bond and how many of each element
H2O – 2 hydrogen atoms, 1 oxygen atom
C2H4O2 – 2 carbons, 4 hydrogen, 2 oxygen
3. Discuss why chemical bonding occurs.
Elements want to be stable (8 valence/outer energy electrons)
Gain, lose, or share electrons to achieve stability
Noble gas = don’t readily make compounds because they are stable
on their own
4. Describe ionic and covalent bonds.
Ionic = when ions attract due to opposite charges
Metal & Non-metal
Good conductors
Elements – gain or lose electrons (ions) NOT SHARING
Covalent = occurs when atoms SHARE electrons
2 nonmetals
5. Identify the particles produced by ionic bonding and by covalent bonding.
Ionic = ions (cation – positive, anion – negative)
Covalent = molecules
6. Distinguish between a nonpolar covalent bond and a polar covalent bond.
Nonpolar = electrons are shared equally, does not have opposite
charged ends, made of identical elements or symmetric (N2, O2)
Polar = electrons are NOT shared equally, slightly positive end and
slightly negative end, (H2O, HCl)
7. Explain how to determine oxidation numbers.
How many electrons an atom must gain, lose, or share to become
stable
Determine from # of electrons, the group, or the charge of the ion
Each group has the same oxidation number, related to the # of
valence/outer energy level electrons
8. Write formulas and names for ionic compounds.
Names = write the name of the cation then the name of the anion
changing the end to “-ide”
NaCl = sodium chloride
Formulas = write the chemical symbol, then criss-cross the oxidation
number/charge
For transition metals their charge is given to us in their name using
roman numerals. If we are given a formula, the charge can be
determined from the anion
9. Write formulas and names for covalent compounds.
Formula = USE GREEK PREFIXES to determine subscripts
Tetranitrogen octachloride = N4Cl8
Name = Greek prefix name of 1st element, greek prefix name of
second element but ending in “-ide”
H2O = dihydrogen monoxide
C6S9 = hexacarbon nonasulfide
C2S = dicarbon monosulfide
Key Concepts
10. Hydrates
Compound with water chemically attached to it
Write the formula as we normally would then add “• _ H2O”
Use Greek prefix to indicate how many water molecules
Ammonium oxide pentahydrate
11. Polyatomic Ions
NAME AND FORMULA NEVER CHANGES
Covalently bonded group of atoms with a negative or positive
charge
Formulas containing polyatomics are ionic and covalent bonds
12. Drawing Lewis Dot diagrams
Visual representation of the electrons
Draw an imaginary box around the chemical symbol then place
electrons on the sides of the box
13. Criss-cross method of balancing ionic compounds
Flip flop the numbers
14. Outer energy level electrons VS. Oxidation numbers
Outer energy level = bonding electrons
Oxidation number = # of outer energy electrons an atom must gain,
lose or share to become stable, same as the charge.