1. Chapter 6.2 – Ionic and Covalent Bonding
Objectives
Why do atoms form bonds?
How do ionic bonds form?
What do atoms joined by covalent bonds share?
What gives metals their distinctive properties?
How are polyatomic ions similar to other ions?

2. Chapter 6.2 – Ionic and Covalent Bonding
atoms bond when their valence electrons interact so that each atom has a full or stable electron configuration
each atom wants to fill its outer s and p sublevels
2 basic kinds of compounds
each type of compound has a different kind of bond

3. Chapter 6.2 – Ionic and Covalent Bonding
ionic compounds
formed from ions
have ionic bonds – an attractive force between oppositely charged ions, which form when electrons are transferred from one to another
one atom loses one or more electrons and another atom or atoms gains them
the oppositely charged ions are then attracted to each other and form an ionic bond

4. Chapter 6.2 – Ionic and Covalent Bonding
ionic compounds form strong networks
because they do not form individual molecules, to write the chemical formulas use the smallest ratio of one ion to another, called the formula unit
NaCl 1:1 Na2O 2:1 AlBr :3
smallest ratio means they will not be divisible by each other and get a whole number
will never have an ionic compound with a 2:2, 6:3, or 2:4 ratio

5. Chapter 6.2 – Ionic and Covalent Bonding
ionic bonds are very strong
therefore ionic compounds are solid at room temperature and have high melting and boiling points
solid ionic compounds do not conduct electricity because their electrons are held tightly by the ions
when melted or dissolved in water, the ions can move and will conduct electricity

6. Chapter 6.2 – Ionic and Covalent Bonding
ionic compounds are neutral
can tell from their formula units
NaCl Na+ Cl :1 ratio
need 1 Na+ for every Cl- to be neutral
MgF2 Mg F :2 ratio
need 2 F- for every Mg2+ to be neutral
Na2S Na+ S :1 ratio
need 2 Na+ for every S2- to be neutral

7. Chapter 6.2 – Ionic and Covalent Bonding
Covalent compounds –
have covalent bonds – bonds formed when atoms share one or more pairs of electrons
- electrons are shared so that both atoms have full outer energy levels
also called molecules
low melting and boiling points
do no conduct electricity
formed between nonmetals

8. Chapter 6.2 – Ionic and Covalent Bonding
the lines in a structural formula show covalent bonds
each line represents 2 electrons that are shared
dots around atoms represent unshared electrons
pairs of electrons stay together in structural formulas

9. Chapter 6.2 – Ionic and Covalent Bonding
atoms can share multiple electrons
when this happens the bonds are stronger
when two pairs of electrons are shared it is called a double bond
when three pairs of electrons are shared it is called a triple bond
when only one pair of electrons are shared it is called a single bond

10. Chapter 6.2 – Ionic and Covalent Bonding
atoms do not always share electrons equally
when electrons are not shared equally the electrons spend more time near one atom than the other
this gives the atoms small charges and the bond is called polar
polar covalent bond –
bond where electrons are shared unequally and the atoms have partial positive and negative charges
ex. H2O, HF, NH3, HCl

11. Chapter 6.2 – Ionic and Covalent Bonding
when atoms share electrons equally the bond is nonpolar nonpolar covalent bond – bond where electrons are shared equally and the atoms are not partially charged ex. H2, Cl2, N2, CH4, CO2

12. Chapter 6.2 – Ionic and Covalent Bonding
Metals form metallic bonds –
bonds between metal cations and the sea of electrons around them
the nuclei form a closest packing structure
the electrons flow around them and do not belong to any one atom
there is a sea of freely moving electrons
this allows metals to flex into sheets or wires without breaking
very strong bonds
high melting and boiling points
conducts electricity well

13. Chapter 6.2 – Ionic and Covalent Bonding
polyatomic ion –
a group of covalently bonded atoms that have a charge
form ionic bonds and ionic compounds with other atoms
acts as a single ion in a compound
polyatomic ions can be positive or negative
polyatomic ions can combine with other ions or other polyatomic ions

14. Chapter 6.2 – Ionic and Covalent Bonding
when more than one of a specific polyatomic ion appears in a compounds name put parentheses around
(NH4)2S Al2(SO4)3 Fe3(PO4)2
the charge of a polyatomic ion applies to the whole ion
many polyatomic ions have oxygen in them
polyatomic ions with many oxygen atoms end with –ate
polyatomic ions with few oxygen atoms end with -ite