1. Ionic and Metallic Bonding
Chapter 7
Ionic and Metallic Bonding

2. 7.1 Ions Valence Electrons
Mendeleev organized his periodic table based on similarities in the properties of elements. Each column of the periodic table is called a group. Each group has the same number of valence electrons.
Valence Electrons- The electrons in the highest occupied energy level of an atom.
Chemical properties of an element are determined by the number of valence electrons.
Determining the number of valence electrons
The number of valence electrons is related to the element’s group number in the periodic table.
For representative elements, the number of the valence electrons is the same as its group number.
Ex: Group 1A elements have 1 valence electron

3. Electron Dot Structures
Electron Dot Structures – Diagrams that show an atom’s valence electrons as dots.
Only valence electrons are involved in chemical bonds.
Octet Rule – Atoms tend to form compounds in a way that allows them to have 8 electrons in their highest occupied energy level.
Metals tend to lose their valence electrons, leaving an octet in the next lowest energy level.
Nonmetals tend to gain or share electrons to form an octet.

5. Formation of Cations
An atom is neutral because the number of protons equals the number of electrons.
An ion forms when an atom gains or loses electrons
A positively charged ion is called a cation
A cation forms when an atom loses one or more valence electrons
For metals:
Cation name is the same as the element name
Sodium Atom (Na) becomes Sodium Ion (Na+)
Even though the names are the same, the properties between sodium atom and sodium ion are very different.
Sodium Metal (atom) reacts explosively with water
Sodium Ion is nonreactive and present in table salt.

6. Formation of Cations Losing Electrons to Form a Cation
Sodium belongs in Group 1A
It can lose 1 valence electron to form a cation with a charge of 1+.
The sodium ion is positive because 1 electron is lost.
There are now 10 electrons total and 11 protons total.
= +1
Magnesium belongs in Group 2A
It can lose 2 valence electrons and form a 2+ charge.

7. Formation of Anions Anion – atom with a negative charge.
Forms when an atom gains one or more valence electrons.
The atom becomes negatively charged because there are more negatively charged electrons than positively charged protons present.

8. Formation of Anions
Anion names of nonmetallic elements are NOT the same as the element name.
The name of the anion ends in –ide
Chlorine atom becomes chloride ion
Oxygen atom becomes oxide ion

9. 7.2 Ionic Bonds and Ionic Compounds
Formation of Ionic Compounds
Ionic Compound – A compound made up of cations and anions.
Ionic compounds are neutral overall
(total positive charge = total negative charge
Example: Sodium Chloride
Ionic Bonds – the force that holds ions together in an ionic compound.
Chemical Formula – Shows the number of atoms of each type of element present in a compound
NaCl is the chemical formula for Sodium Chloride
Formula Unit – lowest whole-number ratio of ions in an ionic compound

10. Predicting Formulas for Ionic Compounds
Use electron dot structures to predict the formulas of the ionic compounds formed from the following elements.
Potassium and Oxygen Magnesium and Nitrogen
K O K
K2O      

11. Properties of Ionic Compounds
Crystalline Solids at room temperature
Ions are arranged in repeating 3-D patterns
High melting points
Conduct electric current when melted or dissolved in water

12. Ionic Naming Shortcut
If the charge of the cation and anion are the same number, drop them.
Na+1 Cl-1  NaCl
Mg+2 S-2  MgS
If the charge of the cation and anion are different, use the …
Criss-Cross Applesauce Rule
Look at the charges the ions make.
Cross the charges and bring down to the subscript position.
Ignore the + or – sign.
Na+1 S-2  Na2S
Mg+2 Cl-1  MgCl2
Na+1 CO3-2  Na2CO3

13. 7.3 Bonding in Metals Metallic Bonds and Metallic Properties
Metals are made up of closely packed cations surrounded by valence electrons. (They are NOT made up of metal atoms)
Valence electrons are free to move from one part of the metal to another.
Metallic Bonds- The forces of attraction between the free-floating valence electrons and the positively charged metal ions.

14. Properties of Metals
The properties of metals are due to the free-floating valence electrons
Metals are ductile – can be drawn into wires
Metals are malleable – can be hammered into shapes
Metals are good conductors of electric current

15. Alloys
Cast Iron
96% Iron
4% Carbon
Alloys- mixtures of two or more elements, at least one of which is a metal.
Examples: Brass = Copper and Zinc
Bronze = Copper and Tin
Steel = Iron and Carbon (some Chromium and Magnesium also)
Alloys have properties better than their individual elements. Steel is harder, tougher and doesn’t rust when compared to Iron.
Sterling silver (92.5 percent silver and 7.5 percent copper) is harder and more durable than pure silver, yet it is still soft enough to be made into jewelry and tableware.