Ionic Compounds and Metals

Bonding and PropertiesChapter 7- pages 204-229

Ions & Ionic Bonding

• Section 7.1: Ion Formation; pg 206-209• Learning Goals:

– I understand how positive ions (cations) and negative ions (anions) are formed.

– I understand why ions form and can relate ion formation to the valence electrons of an element.

• Understanding the above is crucial to understanding chemistry- how elements combine to form compounds and chemical reactions.

Ion Formation

Review• What is the octet rule?• Why do elements form ions?• Which electrons are involved when

ions are formed?• What are positive ions called?• What are negative ions called?

Ion Formation

• All elements are trying to become like a noble gas, in other words become more stable.

• Elements achieve this stability by losing or gaining electrons to reach a full octet of valence electrons.

• Some exceptions to the octet rule are:– Elements 1-5: H, He, Li, Be and B. – Transition metals

Ion FormationAtomic Model

Ion Formation

• Lewis Dot Structures: – a simple shorthand way to represent valence

electrons. – Used as an alternative to electron

configurations and drawing atomic models.– Example: •Na → Na

• Other ways to show ion formation: electron configurations & orbital diagrams.

Lewis Dot Structures

Ion Formation• A cation is a positively charged ion.

– Formed when a neutral element loses electrons.– All group #1 (alkaline metals), group #2 (alkaline

earth metals) and group #13 (boron group) form cations.

• An anion is a negatively charged ion.– Formed when a neutral element gains electrons.– All group #15 (nitrogen group), group #16 (oxygen

group) and group #17 (halogen group) form anions.

• Because it has 4 valence electrons, the carbon group can form both cations and anions, although we generally consider them to have a charge of zero.

Ionic Bonds and Ionic Compounds

Section 7.2, pages 210-217

Ionic Bonding

Learning goals: • Ionic bonds are formed when

electrons are transferred from one atom to another.

• Ionic bonds are held together by electrostatic attraction.

Ionic Bonding

• Chemical Bond- is the force that holds 2 atoms together.

• There are 3 general types of bonding– Ionic: ex. NaCl, CaCl2, FeS– Metallic: ex. copper, iron, brass– Covalent: ex. CH4, C6H12O6

Ionic Bonding:The Formation of Sodium Chloride

Sodium has 1 valence electron

Cl 1s22s22p63s23p5

Na 1s22s22p63s1

Chlorine has 7 valence electrons

An electron transferred gives each an octet

Ionic Bonding:The Formation of Sodium Chloride

Cl- 1s22s22p6 3s23p6

Na+ 1s22s22p6

This transfer forms ions, each with an octet:

Ionic Bonding

• Ionic bonds are held together by electrostatic attraction. This is the force of attraction by opposite charges.

• The atom is held together by the electrostatic attraction of electrons

(e-) and protons (p+).• Ionic compounds are held together by

the electrostatic attraction of the cation (+) and anion (-).

Ionic Bonding• In general metals form cations and

nonmetals form anions.• The oxidation state is the charge on a

given ion.– Na+ oxidation state = +1– Ca+2 oxidation state = +2– Cl- oxidation state = -1

• Some metals can form ions with multiple oxidation states.– Fe+2, Fe+3

– Cu+, Cu+2

Naming Ionic Compounds• A cation retains the name from the element it

was formed from.– Na+ sodium cation– Ca+2 Calcium cation– Al+3 aluminum cation

• An anion is named by adding the suffix -IDE at the end of the name of the element it was formed from.– Cl- chloride anion– S-2 sulfide anion– O-2 oxide anion– N-3 nitride anion

Naming Ionic Compounds

• Ionic compounds are named by combining the names of the cations and the anions.– NaCl sodium chloride– NaF sodium fluoride– CaCl2 calcium chloride– MgO magnesium oxide– FeS iron sulfide

Ionic CompoundsProperties

• The packing of these positively charged cations and negatively charged anions must balance the forces of attraction and repulsion between the atoms.

Ionic CompoundsProperties

• The repeating pattern of particle packing in an ionic compound is called an ionic crystal.

Ionic CompoundsProperties

• A crystal lattice is the three-dimensional geometric arrangement of particles, and is responsible for the structure of many minerals.

Quartz, SiO2 Pyrite, FeS2

Ionic CompoundsProperties

• In a solid, ions are locked into position and electrons cannot flow freely—solid ions are poor conductors of electricity.

• Liquid ions or ions in aqueous solution have electrons that are free to move, so they conduct electricity easily.

• An ion in aqueous solution that conducts electricity is an electrolyte.

Physical Properties of Ionic Compounds

• The properties of ionic compounds can be explained by the strong attractive forces between the cations and anions-electrostatic attraction.

• Ionic compounds have very high melting and boiling points compared to most other solid compounds.

• Ionic bonds are very strong compared to metallic and covalent bonds.

Physical Properties of Ionic Compounds

• Ionic compounds are hard, rigid and brittle

Ionic Bonding

• Positive and negative ions exist in a ratio determined by the number of electrons transferred from the metal atom to the non-metal atom.

• Example:– NaCl – CaCl2

Names and Formulas for Ionic Compounds

• Sodium + Chlorine• Sodium + Oxygen• Potassium + Iodine• Calcium + Oxygen• Calcium + Bromine

Ionic Compounds

• https://www.youtube.com/watch?v=c-nMmwfTV-w

• https://www.youtube.com/watch?v=mukCRQ0GzfQ&feature=related

Ionic Bonding

Oxidation or Charge States of Ions

Assessment

1. Explain how an ionic compound made up of charged particles can be electrically neutral.

2. Name 3 properties of ionic compounds.3. Why are ionic compounds so strong?4. How would you write the following

ionic compounds:a. Potassium and fluorideb. Magnesium and chloridec. Sodium and oxygen

Review on Ionic Bonding

• Which elements/groups form cations? Why?

• Which elements/groups form anions? Why?

Metals & Metallic Bonding

• Section 7.4- pages 225-228.Learning Goals:• I can describe a metallic bond and I

understand how a metallic bond differs from an ionic bond.

• I understand the physical properties of metals and can relate these properties to their valence electrons.

• I can define and describe what alloys are.

Metallic Bonding• Metals form crystal lattices in the solid

state and can be modeled as cations surrounded by a “sea”of freely moving valence electrons.

A metallic bond is the attraction of a metallic cation for these delocalized electrons.

Metallic Bonding

• The metal ions are tightly packed in the crystal and their “d” electron orbitals overlap.

• The electron sea model proposes that all metal atoms in a metallic solid contribute their valence electrons to form a "sea" of electrons.

• The electrons are free to move around and are referred to as delocalized electrons.

Review from last week1. What are the 3 types of bonds?2. Why do ions form?3. What interaction holds ionic bonds

together?4. Last week’s BIG IDEA: oppositely

charged ___________ attract each other, forming electrically _________ ___________ ____________.

5. What ion does Ca form? What is its oxidation state?