Ionic and Covalent Bonding

Ions An ion is an atom with an electric charge. When a metal atom loses an electron to be more stable, it becomes a positive ion because it now has more protons than electrons. When a nonmetal gains an electron, it becomes a negative ion. Na+ K+ Ca2+ Al3+ Cl- O2-

6. What is an ion? 7. What kind of ions do metals form? Nonmetals? 8. Why does calcium chloride(CaCl2) need two atoms of chlorine to be stable? 9. What are three properties of ionic compounds?

Polyatomic Ions When ions are made of more than one atom, they are called polyatomic ions. These atoms behave as a unit. NH4+ -- ammonium ion SO4 2 - -- sulfate CO3 2 - -- carbonate

Ionic Compounds Two oppositely charged ions are attracted to each other and can form an ionic bond. The compound that is formed as a result is called an ionic compound. Ex 1: Na+ + Cl- → NaCl. The ions come together to balance out the charges and form a neutral compound. Ex 2: Rock salt is an ionic compound that needs 2 negative ions of Cl to balance out the +2 charge on Ca. Properties of ionic compounds: usually form crystals. high melting points. can conduct electricity when dissolved in water.

Covalent Bonds A covalent bond forms when two atoms share electrons. It usually forms between 2 nonmetals unlike ionic bonds, which forms between a metal and a nonmetal. The force that holds atoms together in a chemical bond is the attraction each atom’s nucleus has for the shared pair of electrons. When a group of atoms with no electric charge join by covalent bonds, they form a molecule.

1. What is an ion. 2. What kind of ions do metals form. Nonmetals. 3 1. What is an ion? 2. What kind of ions do metals form? Nonmetals? 3. Why does calcium chloride(CaCl2)need two atoms of chlorine? 4. What are three properties of ionic compounds?

Covalent Bonds The number of covalent bonds an atom can form depends on its valence electrons. Ex: oxygen has 6 valence electrons so it can form 2 covalent bonds. When 2 atoms share two pairs of valence electrons, they form a double bond. A triple bond forms when 2 atoms share 3 pairs of valence electrons. Single and triple bonds fluorine gas – F2 water – H2O single bond double bonds

Polar Bonds Some atoms have a stronger pull on the shared pair of electrons than other atoms. As a result, the electrons are pulled more toward one atom than the other. This unequal sharing of electrons is called a polar bond. When electrons are shared equally the bond is called nonpolar.

Element Project Guidelines 1 inch colored border around poster Metal = blue Metalloid = green Nonmetal = yellow For 2-letter chemical symbols, first letter is uppercase, second letter is lowercase Correct: Ca, Ag, Fe Incorrect: AU, ZN Project is due Wednesday, February 20 Neatly write group member names on bottom right corner above border