1. Ionic Bonding (6.1)

2. Review
Valence Electron - an electron that is in the highest occupied energy level of an atom
Key role in chemical reactions
The number of the group matches the number of valence electrons
Elements in a group have similar properties because they have the same number of valence electrons

4. Stable Electron Configurations
When the highest occupied energy level of an atom is filled with electrons, the atom is stable and not likely to react
Nobel gases have stable electron configurations with eight valence electrons (helium only has two)
The chemical properties of an element depend on the number of valence electrons

5. Electron Dot Diagram
Model of an atom in which each dot represents a valence electron
The symbol at the center represents the nucleus and all other electrons in the atom

6. Ionic Bonds
Some elements achieve stable electron configurations through the transfer of electrons between atoms

7. Transfer of Electrons
Chlorine is one electron short of having 8 valence electrons
Sodium has one too many electrons to be stable
Sodium transfers its “extra” electron to chlorine to make both atoms more stable

8. Formation of Ions
When an atom gains or loses electrons its charge is no longer neutral
Ion - an atom that has a net positive or negative electric charge
Anion - an ion with a negative charge
Named by using part of the element name plus the suffix -ide
Example: Cl- is called a chloride ion
Cation - an ion with a positive charge
Named by using the element name
Example: Na+ is called a sodium ion

9. When an anion and cation are close together the form chemical bonds because opposite charges attract
Chemical Bond - the force that holds atoms or ions together as a unit
Ionic Bond -the force that holds cations and anions together
Form when electrons are transferred from one atom to another

10. Ionization Energy
Amount of energy used to remove an electron from an atom of an element
The energy allows the electrons to overcome the attraction of the protons in the nucleus
Varies from element to element
The lower the ionization energy, the easier it is to remove an electron from an atom

11. Ionic Compounds Compounds that contain ionic bonds
Chemical Formula - a notation that shows what elements a compound contains and the ratio of atoms or ions of these elements in the compound
Examples:
Sodium chloride is NaCl
Magnesium chloride is MgCl2
Subscript is used to show the relative numbers of atoms of the elements present.
If there is only one atom of an element in the formula no subscript is used

12. Crystal Lattices Repeating pattern of ions in fixed positions
Crystals - solids whose particles are arranged in a lattice structure
Classified into groups based on the shape of their crystals
The arrangement of the ions depends on the ratio of ions and their relative sizes

13. Properties of Ionic Compounds
The properties of an ionic compound can be explained by the strong attractions among ions within a crystal lattice
Properties
High melting point because of strong attractions between particles = more energy needed to separate them
Poor conductor of electricity as solids because of the structure but good conductors as liquids
Crystals shatter when struck because the like charged ions repel each other