COS 3.0, 3.1
CONTRAST THE FORMATION OF IONIC AND COVALENT BONDS BASED ON THE TRANSFER OR SHARING OF VALENCE ELECTRONS.
DEMOSTRATE THE FORMATION OF POSITIVE AND NEGATIVE MONATOMIC IONS BY USING ELECTRON DOT DIAGRAMS.
WHAT YOU’LL LEARN
• Identify the number of valence electrons an element has based on its position on the periodic table.
• Construct electron dot diagrams (Lewis structures) based upon the number of valence electrons given for an element(s).
• Describe ionic & covalent bonds.• Explain why some atoms transfer their valence
electrons to form ionic bonds, while other atoms share valence electrons to form covalent bonds.
VALENCE ELECTRONS
• found in outermost shell of an atom
• determines atom’s chemical properties.
So how do we know number of valence electrons an element has?
• based on their group on periodic table.
• REFER TO PERIODIC TABLE & LABEL
OXIDATION NUMBERS
• AKA: charge
• change in oxidation number represents number of electrons gained or lost in a chemical reaction.
• REFER PERIODIC TABLE & LABEL
Lewis Structures
• AKA: electron-dot structures or electron-dot diagrams.
• Uses number of valence electrons.• indicated by dots placed element’s
symbol. • diagram that shows bonding between
atoms of a molecule.• Always place element with largest number
of valence electrons first, next largest …• form ionic & covalent bonds
The Octet Rule
Atoms tend to gain, lose, or share electrons until they have eight valence electrons.
Ionic BondsIonic Bonds
• TRANSFER of electrons from one bonding atom to another
• Occurs when electron transfers from a metal to a nonmetal
COVALENT BONDINGCOVALENT BONDING
SHARING of electrons between two bonding atoms
Occurs when electron shares Occurs when electron shares between nonmetals