Ionic Bonding

 Students know atoms combine to form molecules by sharing electrons to form covalent or metallic bonds or by exchanging electrons to form ionic bonds.  Students know salt crystals, such as NaCl, are repeating patterns of positive and negative ions held together by electrostatic attraction.  Students know atoms combine to form molecules by sharing electrons to form covalent or metallic bonds or by exchanging electrons to form ionic bonds.  Students know salt crystals, such as NaCl, are repeating patterns of positive and negative ions held together by electrostatic attraction.

Bonds Forces that hold groups of atoms  Forces that hold groups of atoms together and make them function together and make them function as a unit. as a unit.  Ionic bonds – transfer of electrons  Covalent bonds – sharing of electrons

The Octet Rule – Ionic Compounds Ionic compounds form so that each atom, by gaining or losing electrons, has an octet of electrons in its highest occupied energy level. Metals lose electrons to form positively-charged cations Nonmetals gains electrons to form negatively- charged anions

Ionic Bonding: The Formation of Sodium Chloride  Sodium has 1 valence electron Cl: 1s 2 2s 2 2p 6 3s 2 3p 5 Na: 1s 2 2s 2 2p 6 3s 1  Chlorine has 7 valence electrons  An electron transferred gives each an octet

Ionic Bonding: The Formation of Sodium Chloride Cl - 1s 2 2s 2 2p 6 3s 2 3p 6 Na + 1s 2 2s 2 2p 6 This transfer forms ions, each with an octet:

Ionic Bonding: The Formation of Sodium Chloride Cl - Na + The resulting ions come together due to electrostatic attraction (opposites attract): The net charge on the compound must equal zero

Ionic Bonds Metal to Nonmetal High END Metal forms cation Nonmetal forms anion

Sodium Chloride Crystal Lattice Ionic compounds form solid crystals at ordinary temperatures. Ionic compounds organize in a characteristic crystal lattice of alternating positive and negative ions. All salts are ionic compounds and form crystals.

Ionic solids are brittle Force Strong repulsion breaks crystal apart.

Visual Concept Characteristics of Ion Bonding in a Crystal Lattice

Properties of Ionic Compounds

Lattice Energy- the ionic bond ---the energy released when the crystal lattice formation is formed ---Lattice energies are listed as negative values to indicate that energy is given off when ions come together to form the ionic crystal. The greater the lattice energy… the stronger the ionic bonding!

Vocabulary COMPOUND ternary compound binary compound 2 elements more than 2 elements NaNO 3 NaCl

Vocabulary ION polyatomic Ion monatomic Ion 1 atom 2 or more atoms NO 3 - Na +

e-e- 3p+3p+ lithium atom Li e-e- loss of one valence electron e-e- e-e- lithium ion Li + 3p+3p+ e-e- e-e- 9p+9p+ fluorine atom F e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- gain of one valence electron fluoride ion F 1- 9p+9p+ e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e-

Formation of Cation 3p+3p+ lithium atom Li e-e- loss of one valence electron e-e- e-e- lithium ion Li + 3p+3p+ e-e- e-e- e-e-

Formation of Anion 9p+9p+ fluorine atom F e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- gain of one valence electron fluoride ion F 1- 9p+9p+ e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e-

Formation of Ionic Bond fluoride ion F 1- 9p+9p+ e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- lithium ion Li + 3p+3p+ e-e- e-e-

Ionic bonding: Li + Cl 1e - 3p + 4n 0 2e - 17p + 18n 0 8e - 8e - 2e 3p + 4n 0 2e - 1e - 17p + 18n 0 7e - 8e - 2e - Li Cl [ Cl ] – [Li] + lithium atomchlorine atomlithium ionchloride ion

Ionic bonding: Li + C Li + Cl  [ Cl ] – [Li] + Ionic compound formation equation

Ionic bonding: Mg + O 12p + 12n 0 2e - 8e - 2e - 1e - [ O ] 2– [Mg] 2+ 6e - 2e - 8n 0 8p + 1e - 8e - 2e - 8n 0 8p + 12p + 12n 0 2e - 8e - O Mg

Lewis Dot Diagrams and BONDING (Ionic )

How do we show the valence electrons for different elements? * dot diagrams were developed by American, G.N. Lewis, in the 1920's * they are called Lewis structure or Lewis dot diagrams

Electron-Dot Notation To keep track of valence electrons, it is helpful to use electron-dot notation. Electron-dot notation shows only the valence electrons of an atom of a particular element, indicated by dots placed around the element’s symbol. The inner-shell electrons are not shown.

Click below to watch the Visual Concept. Visual Concept Electron-Dot Notation

Hydrogen has one valence electron Nitrogen has five valence electrons.

Mg Write the electron dot diagram for Na Mg C O F Ne He 1s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 3s 2 1s22s22p21s22s22p2 1s22s22p41s22s22p4 1s22s22p51s22s22p5 1s22s22p61s22s22p6 1s21s2 Na C O F He Ne

Ionic Bonding NaCl transfer of electron +1 NaCl

Ca +2 P -3 Ca +2 P All the electrons must be accounted for! Ionic Bonding Ca -3

Ionic Bonding Ca 3 P 2 Formula Unit Ca 2+ P 3- Ca 2+ P 3- Ca 2+ P 3- Ca 2+

Ionic Formation Equation Ca P + 2[ P ] –3 3[Ca] +2

* monatomic ions can be written with dot diagrams * as before, dots are used to demonstrate e- * symbol is in [brackets] to represent ions * charge is placed on the upper right corner

Do the dot diagrams for Na, Mg, Al, P, S, Cl ions

Practice Draw the Lewis Dot Diagrams for the following compounds: 1.Lithium iodide 2.Calcium chloride 3.Potassium oxide Example: Magnesium Chloride [Mg] +2 2[ Cl ] -1

Polyatomic Ions An example of a polyatomic ion is the ammonium ion:. It is sometimes written as to show that the group of atoms as a whole has a charge of +1. The charge of the ammonium ion is determined as follows: seven protons in the nitrogen atom plus the four protons in the four hydrogen atoms give the ammonium ion a total positive charge of +11.

When nitrogen and hydrogen atoms combine to form an ammonium ion, one of their electrons is lost, giving the polyatomic ion a total negative charge of -10. The total charge is therefore (+11) + (-10) = +1.

Some examples of Lewis structures of polyatomic ions are shown below.