Ionic Bonding

Ionic Bond Electrostatic attraction that holds ions together Electrostatic force – like charges repel, opposite charges attract How do we get ionic bonds? When an atom gains an electron its called? When an atom loses an electron its called? Electrostatic force tells us that cations and anions should? Can an ionic bond consist of two anions or cations?

Cations Atom or group of atoms with a positive charge from the loss of valence electron(s) Ca “+” ion All metals are cations Reactivity is based on the ease in which they lose a valence electron What do metals do in order to achieve a stable octet? If a metal is very reactive will it have high or low ionization energy?

Na atom Na 1s22s22p63s1 Na ion (lost 1 electron) Na+ 1s22s22p6 Mg atom Mg 1s22s22p63s2 Mg ion (lost 2 electrons) Mg2+ Al atom Al 1s22s22p63s23p1 Al ion (lost 3 electrons) Al3+ Ne atom (noble gas) Ne

Anions Atom or group of atoms with a negative charge from the gain electron(s) Tend to be nonmetals Cl atom Cl 1s22s22p63s23p5 Cl ion (gain 1 electron) Cl- 1s22s22p63s23p6 S atom S 1s22s22p63s23p4 S ion (gain 2 electrons) S2- Ar atom Ar If atoms lost electrons to become positive, what do you think atoms do to become negative? What kind of electrons are gained? Why are they gaining electrons?

Monatomic Ions +1 +2 +3 -3 -2 -1

We can use our lewis dot diagrams in an equation to model ionic bonding

Ionic Compounds Held together by ionic bonds Composed of ions Cation and anion Usually a metal and nonmetal Electrically neutral Ex: salts

Formula Unit Lowest whole-number ratio of ions that form form an ionic compound The cation is always written before the anion Ionic compounds carry what charge? So this means our cations and anions have to do what?

Atoms Cation Anion Ratio Formula Unit Na and Cl Na+ Cl− 1:1 NaCl Mg and O Mg2+ O2− MgO Na and O 2:1 Na2O Al and Br Al3+ Br− 1:3 AlBr3 Ionic compounds are electrically what? **Total positive charge of the cations equals the total negative charge of the anions

Example 1 Predict the compound formed when magnesium and nitrogen combine. Start with the atoms Write their ions Crisscross charges to get neutral compound Write formula unit Mg N Mg2+ N3− Mg3N2

Example 2 Predict the compound formed when magnesium and nitrate combine. Start with the atoms Write their ions Crisscross charges to get neutral compound Write formula unit Mg NO3 Mg2+ NO3− Mg(NO3)2

Properties Strong bonds High melting and boiling points Solid at room temperature Hard, rigid, and brittle When dissolved in water or melted it can conduct an electric current

Electrolyte Salt dissolving in water animation All stalts are ionic compounds but not all ionic compounds are salts

Crystal Lattice Structure of ionic compounds Repeating 3-D pattern (alternating cation & anion) Large attractive forces result in a very stable structure Where do these attractive forces come from?