Understanding Ionic Bonding in Chemistry

1. Chemical Bonding Notes Chapter 8

2. Ionic Bond Notes Chapter 8 – Section 2

3. Forming Ionic Bonds • An ionic bondforms when valence electrons are transferred from one atom to another atom. • In an ionic bond, one atom has lost electrons and the other atom has gained electrons. • Example:NaCl Na (1 valence electron) – easy to lose an electron and Cl (7 valence electrons) – easy to gain an electron

4. Forming Positive Ions • Because atoms of most metals have few electrons in their outermost energy level, metal atoms tend to lose valence electrons and form positive ions. • Energy is needed to remove electrons from atoms, this is called ionization energy. • elements in Groups 1 and 2 react very easily because the they have low ionization energy

5. Forming Negative Ions • Because the outermost energy level of nonmetal atoms is almost full, during chemical changes the atoms of nonmetals tend to gain electrons and form negative ions. • Energy is released when most nonmetal atoms gain electrons. • The more easily an atom gains an electron, the more energy the atom releases (reason Group 17 is a very reactive nonmetal group)

6. Ions • If an atom loses electrons (ex. metals) it becomes a positive ion or cation (has more protons than electrons) - Potassium (K) = K 1+ (it loses an electron so it has one more proton than electron) • If an atom gains electrons (ex. nonmetals) it becomes a negative ion or anion (has more electrons than protons. - Chlorine (Cl)= Cl 1- (it gains an electron so it has one more electron than proton)

8. Forming Ionic Compounds • An ionic bond forms when valence electrons are transferred from one atom to another atom. • In an ionic bond, one atom has lost electrons and the other atom has gained electrons making them stick together. • The compound formed is neutral because the charges cancel each other (+ and – cancel out) • When a metal and a nonmetal combine by ionic bonding, the compound formed has different properties than the metal and nonmetal did.

9. Ionic Solids • have a definite melting point and contain ionic bonds • example: sodium chloride (NaCl) • a type of crystalline solid • form when electrostatic attraction sticks together anions (-) and cations (+) to form a crystal lattice • each ion is surrounded by ions having an opposite charge • are extremely stable since considerable energy is required to break ionic bonds

10. Ionic Solids (cont) • Instead of calling a single unit a molecule it is called a formula unit. • X-ray crystallography is used to determine the actual structure. • Diffraction patterns of x-rays show the structure • Because + & - ions alternate, stress can cause layers of ions with like charges to line up, repel, shatter & be brittle

11. Ionic Bonding Examples: • Naming… Positive ion comes first (usually a metal) and if negative ion is an element change ending to –ide. NaCl Sodium Chloride • Na + Cl = Na 1+ + Cl 1- = name: • Li + O = Li 1+ + O 2- = Name = • Al + S = Al 3+ + S 2- = Name = Li2O Lithium Oxide Al2S3 Aluminum Sulfide

12. Ionic Nomenclature (naming) • Positive ion comes first (usually a metal) and if negative ion is an element change ending to –ide. • Acids start with H • -OH is a hydroxide group • Polyatomic ion names

14. Polyatomic Ions • Ions made of more than one atom • Act as one in terms of overall charge • Example: (CO32-) – can combine with Calcium (Ca2+) and become calcium carbonate (CaCO3)