aka Electrovalent bonds Ionic Bonding aka Electrovalent bonds

Ionic Bond Chemical bond resulting from electrostatic attraction between positive and negative ions. Goal: achieve stable octet of electrons (noble gas configuration) Illustrate by Orbital notation Lewis Dot diagrams

Three Types of Bonding Ionic Covalent Metallic electrons are transferred. Covalent electrons are shared. Metallic “sea of mobile electrons.”

Identify Bond Type from Formula Ionic Compounds metal + nonmetal Covalent Compounds all nonmetals Metallic all metals Salts

Force of Attraction

Show transfer of VALENCE electrons to achieve octet But WHICH electrons (i.e. what orbitals) are involved?                                                                     Formation of The Octets A quantum mechanical representation of the electron transfer

Na metal  Cations Metals lose e-

Anions Nonmetals gain e- Cl2 (g) 

Ionic Compounds metal + nonmetal Composed of positive and negative ions combined so that compound is NEUTRAL. Most ionic compounds are … crystalline solids. Expressed as Formula Units, not molecules (which are covalent)! Simplest ratio of atoms (empirical formula) metal + nonmetal

Structure of Ionic Compounds Ions are attracted to each other by strong electrostatic interactions. Form a crystal lattice a regular 3-D pattern or array. Ions are held in fixed positions in the solid state. Unit Cell = smallest repetitive unit in lattice

Electron is transferred from Na to Cl Tiger Graphic

Ionic Reactions Exothermic release HEAT

Strength of Ionic Bond Na+(g) + Cl−(g) → NaCl(s) Lattice Energy Energy released when one mole of an ionic crystalline compound is formed from gaseous ions. Na+(g) + Cl−(g) → NaCl(s) The experimental lattice energy of NaCl is −787 kJ/mol. Shown as negative value  Exothermic

Trends in Lattice Energy Interionic Distance Increases as Lattice Energy Decreases LiF LiCl LiI

Trends in Lattice Energy State the trend here…

Factors that Affect Lattice Energy Related to the SIZE of the ions bonded. Smaller ions generally have a more negative (larger) lattice energy. Affected by the CHARGE on the ion. Larger charged atoms generally have a more negative (larger) lattice energy

Oxidation Number Determines how many atoms are needed to form the ionic compound.

means greater stability! Ionic Bond Formation Release ENERGY Decreasing energy means greater stability! NaCl Na + Cl Potential Energy

Properties of Ionic Compounds Memorize! High melting points Low vapor pressures Solids do not conduct electricity Melts (liquids) do conduct electricity Solutions (aq) conduct electricity electrolytes: substances whose water solution conducts an electric current. Tend to be hard and brittle High solubility in water.

Linus Pauling 1954 Nobel Prize Chemistry First to show that chemical bonds could show degrees of both a covalent and ionic nature. Led to the development of electronegativity values.

Electronegativity Difference 1.7

Electronegavitity Difference Bonding between atoms is a continuum from ionic to covalent. The larger the difference in electronegativity between two bonded elements, the more ionic in character the bond has. Which has more ionic character? CaO or KF or LiH

Crystal Coordination Number The coordination number of an atom in a molecule or a crystal is the integer number of its nearest neighbors.

Salt Crystals - Cubic