Chapter 6
Chemical Bonds
6.1 Ionic Bonding
• Stable Electron Configurations
▫ When the highest occupied energy level of an atom is
filled with electrons, the atom is stable and will NOT
react.
 Ex: Noble Gases (8 valence electrons) and Helium (2 v.e.)
Electron Dot Diagrams
• Electron Dot Diagrams (Lewis Structures) is a
model of an atom in which each dot represents a
valence electron
Ionic Bonds
• Elements that do not have complete sets of
valence electrons will be reactive. By reacting,
they can achieve complete sets.
• Some elements achieve stable electron
configurations through the transfer of electrons
between atoms.
Formation of Ions
• When an atom gains or loses an electron, the
protons do not equal the electrons. The atom is
no longer neutral.
• Ion- Atom that has a net positive or negative
charge.
▫ Anion- Ion with a negative charge.
 To name an anion, you change the suffix to –ide and
add ion.
 Ex: Chloride ion
▫ Cation- Ion with a positive charge.
 To name a cation, you add ion to the end.
 Ex: Sodium ion
Formation of Ionic Bonds
• Chemical Bond- force that holds atoms or ions together.
• Ionic Bond- force that holds anions and cations together.
▫ An ionic bond forms when electrons are transferred from
one atom to another
• Ionization Energy- the amount of energy needed to
remove an electron.
▫ The lower the ionization energy, the easier it is to remove
an electron.
 It’s easier to
remove an
electron from
a metal than
from a
nonmetal
Ionic Compounds
• A chemical formula is a notation that shows
what elements a compound contains and the
ratio of the atoms or ions of these elements in
the compound.
▫ Ex: MgCl2
Ionic Compound Diagrams to try:
• K and Cl
Li and S
• Sr and Cl
Al and N
• *Ga and S
Crystal Lattices
• Remember that orderly, 3-D structure of solids?
▫ In NaCl, each chloride ion is surrounded by 6 sodium ions
and each sodium ion is surrounded by 6 chloride ions.
▫ The opposite charges keep ions in their fixed positions in a
rigid framework, or lattice.
• Crystals- Solids whose particles are arranged in a lattice
structure.
Properties of Ionic Compounds
• The properties of an ionic compound can be explained by
the strong attractions among ions.
▫ high melting point
▫ poor conductor of electricity when solid, good conductor
when melted.
▫ shatter when struck by a hammer
6.2 Covalent Bonds
• Sharing Electrons
▫ H has 1 electron. If it had two electrons, it would be happy.
(It would have a full outer energy level.)
▫ Two H atoms can share their electrons
• Covalent Bond- chemical bond in which 2 atoms share a
pair of valence electrons.
▫ When two atoms share 1 pair of electrons, the bond is a
single bond.
Molecules of Elements
• Two hydrogen atoms bonded together form a
unit called a molecule
• Molecule- neutral group of atoms that are joined
together by one or more covalent bonds
• The attractions between the shared electrons
and the protons in each nucleus hold the atoms
together in a covalent bond.
Diatomic Molecules & Multiple
Covalent Bonds
• Diatomic Molecules- occurs
in many nonmetals. It’s two
atoms of the same element.
▫ Ex: Halogen Group
▫ HONClBrIF
• Multiple Covalent Bonds
• Nitrogen has 5 valence
electrons. It needs to share
3 pairs of electrons in order
to be happy.
Unequal Sharing of Electrons
• In general, elements on the right of the periodic
table have a greater attraction for electrons.
▫ Fluorine has the strongest attraction.
• Polar Covalent Bonds
▫ Electrons are not shared equally. Ex: H-Cl
▫ Electrons will hang out by Cl, giving it a slight
negative charge. The other atom will have a slight
positive charge.
Shared electrons in a
hydrogen chloride molecule
spend less time near the
hydrogen atom than near
the chlorine atom.
• Nonpolar Covalent Bonds
▫ Electrons are shared equally.
 Polar molecules have stronger attractions to each
other.
6.3 Naming Compounds and Writing Formulas
• Naming Ionic
Compounds
▫ Binary Ionic
Compounds – Made
from only 2 elements
– 1 metal and 1
nonmetal
 Cation first followed
by anion.
 Change the ending of
the anion to -ide
6.3 Naming Compounds and Writing Formulas
• Writing Formulas for Ionic Compounds
▫ Place the symbol of the cation first, followed by
the symbol for the anion.
▫ Use subscripts to show the ratio of the ions in the
compound (all compounds must be neutral)
 Use criss-cross method
6.3 Naming Compounds and Writing Formulas
• Naming Molecular Compounds
▫ The more metallic element appears
first.
▫ The name of the second element
changes its ending to –ide.
 Ex: carbon dioxide
▫ Use the Greek prefixes to reflect the
number of atoms of each element.
 Ex: dinitrogen tetraoxide N2O4
▫ If mono appears in the first
element, the prefix is dropped.
 Ex: NO2 mononitrogen dioxide
becomes nitrogen dioxide.
6.3 Naming Compounds and Writing Formulas
• Writing Molecular Formulas
▫ Write the symbols for the elements in the order
the elements appear in the name
▫ Prefixes indicate the number of atoms of each
element – they become subscripts
 If there is no prefix, there is only 1 atom
 Ex: Diphosphorus tetrafluoride
P2F4
6.4 The Structure of Metals
• Remember, metals like to lose electrons.
• What happens if no nonmetals are present to accept
the extra electrons?
▫ In a metal, valence electrons are free to move along the
atoms.
▫ Metal atoms become cations surrounded by a “sea of
electrons”
• Metallic Bond- the attraction between a metal cation
and the shared electrons that surround it.
▫ The cations in a metal form a lattice that is held in
place by the strong metallic bonds between cations
and the surrounding valence electrons.
▫ Overall, a metal is neutral because the total number of
electrons does not change.
The sea of valence electrons can explain
the various properties of metals
• 1. Alkali metals are very soft. The bonds between the cations
and the electrons are very weak because each metal only
contributes 1 valence electron.
• 2. An electric current is a flow of charged particles. Metals
have a built-in flow of charged particles.
• 3. Metals are malleable. When metal is struck with a hammer,
the metal ions shift their position and the shape changes
In a metal, cations are
surrounded by shared
valence electrons. If a
metal is struck, the
ions move to new
positions, but the ions
are still surrounded by
electrons.
Alloys
• Gold is a soft metal. It becomes harder when
mixed with Ag, Cu, Ni, or Zn
• Alloy – A mixture of two or more elements, at
least one of which is a metal.
▫ Alloys have the characteristic properties of metals.
▫ EX:
 Gold that is 100 percent pure is labeled 24-karat
gold.
 Gold jewelry that has a 12-karat label is only 50
percent gold.
 Jewelry that has an 18-karat label is 75 percent gold.