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Unit 7, Chapter 19
Integrated Science
Chapter 19 Learning Goals Relate the chemical behavior of an element, including bonding, to
its placement on the periodic table.
Identify how elements form chemical bonds and the role of electrons in bonding.
Predict the chemical formulas of compounds made up of two different elements.
Write chemical formulas for compounds made up of many different types of elements.
Calculate the formula mass of a compound and compare different compounds based on their formula masses.
Identify the environmental and economic impact of recycling plastics.
Chapter 19 Vocabulary Terms ionic bond
monoatomic ion
octet subscript
polymer
polyatomic ion
react
valence electron
Avogadro number
chemical bond
chemical formula
covalent bond
diatomic molecule
energy level
formula mass
ion
19.1 Bonding and Molecules
Key Question:
Why do atoms form chemical bonds?
*Read text section 19.1 AFTER Investigation
19.1
19.1 Bonding and Molecules The outer electrons are
involved in bonding. These are called
valence electrons. Most stable atoms have
eight valence electrons. (Some have two)
When an atom has 8 valence electrons, it is said to have an octet of electrons.
8
7
6
5
1
2
3
4
19.1 The Octet Rule
19.1 Bonding and Molecules
A sodium atom is chemically unstable because it has only one valence electron.
With the exception of the transition metals, the column of the table tells you how many valence electrons each element has. Columns are called groups.
For example, the atoms of the elements in Group 1A have only one valence electron.
1
If it helps put the valence e- in ()
Group 1 the alkali metals or lithium family
Group 2 the alkaline earth metals or beryllium family
Group 3 scandium family (consisting of the rare earth elements plus the actinides)
Group 4 the titanium family
Group 5 the vanadium family
Group 6 the chromium family
Group 7 the manganese family
Group 8 the iron family
Group 9 the cobalt family
Group 10 the nickel family
Group 11 the coinage metals (not an IUPAC-recommended name) or copper family
Group 12 the zinc family
Group 13 the boron group or boron family
Group 14 the carbon group or carbon family
Group 15 the pnictogens or nitrogen family
Group 16 the chalcogens or oxygen family
Group 17 the halogens or fluorine family
Group 18 the noble gases or helium family or neon family
Lewis Dot StructuresCount the total valence electrons for the
molecule
Figure out how many octet electrons the molecule should have, using the octet rule:— All atoms want 8 except for H and He = 2
If the number is 3 or less atom gives up those negative e-!
If the number is 4 or more atom will gain enough e- to make 8.
19.1 Ionic Bonds Ionic bonds are formed when atoms gain or lose electrons.
Sodium and chlorine form an ionic bond to make sodium chloride (table salt).
19.1 Covalent BondsWhen electrons are shared between two
atoms, a covalent bond is formed.
19.1 Ionic or Covalent Bond? Elements can be
classified as metals, metalloids, and nonmetals.
Generally, bonds between a metal and a nonmetal tend to be ionic in character.
Bonds between two nonmetals can be classified as covalent.
19.2 Chemical Formulas
Key Question:
Why do atoms combine in certain ratios?
*Read text section 19.2 AFTER Investigation 19.2
19.2 Chemical Formulas All compounds
have an electrical charge of zero; that is, they are neutral.
19.2 Oxidation Number
An oxidation number indicates how many electrons are lost, gained, or shared when bonding occurs.
Common Polyatomic Ions
19.3 Comparing MoleculesKey Question:
What is the meaning of a chemical formula?
*Read text section 19.3 AFTER Investigation 19.3
19.3 Comparing Molecules
One atom of hydrogen is 1/12 the mass of a carbon atom.
19.3 Comparing Molecules
19.3 Comparing Compounds The Avogadro number is the
number of atoms in the atomic mass of an element or the number of molecules in the formula mass of a compound when these masses are expressed in grams.
One set of 6.02 x 1023 atoms or molecules is also referred to as a mole of that substance.
