Ch. 7: Ionic Compounds &
Metals
Sec. 7.1: Ion Formation
Forming Chemical Bonds
• Objectives
– Define chemical bond.
– Relate ionic bond formation to electron
configuration.
– Describe the formation of positive and negative
ions.
Forming Chemical Bonds
• How do thousands of compounds form from
the relatively few elements known to exist?
Forming Chemical Bonds
• Valence electrons are the electrons involved
in the formation of chemical bonds between
two atoms.
Forming Chemical Bonds
• A chemical bond is the force that holds two
atoms together.
• Chemical bonds are due to:
– the attraction between a positive nucleus of one
atom and the negative electrons of another
(covalent), OR
– The attraction between a positive ion and a
negative ion (ionic)
Forming Positive Ions
• Recall the octet rule ….
• Recall: metals have low ionization energy
& electronegativity (meaning…?)
• Recall: metals form positive ions
• A positive ion forms when an atom loses
one or more valence electrons in order to
attain a noble gas configuration.
Example
• Neon
1s22s22p6
• Sodium atom
• Sodium ion
1s22s22p63s1
1s22s22p6
• A positively charged ion is called a
cation.
Forming cations
• Sodium atom (Na)
– 11 protons
– 12 neutrons
– 11 electrons
• Sodium ion (Na+)
– 11 protons
– 12 neutrons
– 10 electrons
SAME electron configuration as neon but
it is NOT neon.
Reactivity of metals
• Depends on how easily they lose their
valence electrons
– Group 1A (1+ ions): very easily ---> highly
reactive
– Group 2A (2+ ions): relatively easy ---> very
reactive
– Group 3A (3+ ions): easily ---> reactive
Transition Metals
• When forming positive ions, transition metals
commonly lose their two “s” electrons, forming
2+ ions.
• It is also possible for the d electrons to be lost,
forming other relatively stable electron
arrangements. These are referred to as pseudonoble gas configurations.
• Therefore, most transition elements can form
more than one kind of ion
– For example, Fe can form a 2+ OR 3+ ion.
Forming Negative ions
• Recall octet rule; Recall the high ionization
energy and electronegativity of nonmetals
• Nonmetals form a stable outer electron
configuration by gaining 1 or more
electrons.
Forming Anions
Argon
1s22s22p63s23p6
Chlorine 1s22s22p63s23p5
Cl1s22s22p63s23p6
• By gaining a single electron, a chlorine atom
attains the electron configuration of argon.
• With the addition of one electron, chlorine
becomes a negatively charged ion called an
anion.
Forming Anions
• To name an anion, the ending –ide is added
to the root name of the element.
• The anion of chlorine is called chloride.
• What is the anion of nitrogen called?
arsenic?
Let’s look at nitrogen . . .
• Nitrogen atom (N)
– 7 protons
– 7 neutrons
– 7 electrons
• Nitride ion (N3-)
– 7 protons
– 7 neutrons
– 10 electrons
SAME electron configuration as neon but
it is NOT neon
General Trends
• Group 5A/15: gain 3 e-’s and become 3ions
• Group 6A/16: gain 2 e-’s and become 2ions
• Group 7A/17: gain 1 e- and become 1- ions