Ionic Bonding .

Why do bonds/compounds form? Valence Electrons Electrons in highest energy level Largely responsible for chemical behavior (properties, bonding) Noble gases have eight valence electrons. They are unreactive…meaning they don’t form bonds or compounds. Eight valence electrons is important in the stability of atoms.

Octet Rule Octet Rule: atoms tend to gain, lose, or share electrons in order to acquire a full set of 8 valence electrons. All atoms want to have eight valence electrons…to be stable.

Forming a + Ion How does a positive ion form? Positive ions are formed by losing electrons. Atoms lose as few electrons as possible in order to achieve noble gas configuration or the octet rule. Remember, low ionization energy is best for losing electrons. Where are the elements that are most likely to lose electrons? On the left side…metals! Metals form + ions.

Stability of Ion A positive ion is called a cation. Consider stability. Which is more stable: a neutral Na atom or a Na+ ion? Hint: Which has an electron configuration or a number of valence electrons closer to the noble gases? The sodium ion is more stable.

Forming a - Ion Remember, electronegativity involves attracting electrons, and a negative ion is formed by gaining electrons. A high electronegativity is helpful in forming a negative ion. Where are elements found that are most likely to gain an electron forming a negative ion? On the right side of the table…nonmetals! Nonmetals form –ions.

Stability of Ion What is more stable a neutral chlorine atom or a Cl-? The chlorine ion has an electron configuration similar to a noble gas. SIMPLE: All atoms want an electron configuration like a noble gas. They will gain or lose as few electrons as possible to do so.

Naming Cations Name of parent element + “ion” Indicate charge of transition metals in parentheses Mg2+ magnesium ion Na+ sodium ion Cu2+ copper (II) ion Al3+ aluminum ion

Naming Anions Root of parent atom + suffix “-ide” Cl chlorine atom Cl- chloride ion F fluorine atom F- fluoride ion O oxygen atom O2- oxide ion

Forming Chemical Bonds Chemical bond: force that holds 2 atoms together (holds compounds together) Valence electrons are involved in the formation of chemical bonds between atoms.

Formation and Nature of Ionic Bonds Opposites _____________________. Let’s look at a reaction between sodium and chlorine. Sodium likes to lose electrons to become a cation. Chlorine likes to gain electrons to become an anion. A bond forms between the ions called an ionic bond.

Opposites Attract!

Ionic Bond Ionic bond: the electrostatic force that holds oppositely charged particles together in an ionic compound Compounds that contain ionic bonds are called ionic compounds. Ionic compounds form between metals and nonmetals. Ex.: Na+ and Cl- form NaCl

Properties of Ionic Compounds Formula units give the proportions and identities of atoms that come together to form unit cells of ionic compounds. Unit cells are order arrangements of ions that minimize repulsive forces. Coordination number: ion is the number of ions of opposite charge that surround the ion in a crystal.

Unit cells form beautiful crystals… Ionic compounds are crystals!