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
1 ve
2 ve3 ve
4 ve5 ve
6 ve7 ve
8 ve
Lets find some valence electrons.
• Si • Xe• K• Ba• I• O• Al• P
OXIDATION NUMBERS
• AKA: charge
• change in oxidation number represents number of electrons gained or lost in a chemical reaction.
• REFER PERIODIC TABLE & LABEL
+1
+2+3
+4-3
-2
-1
Lets find some oxidation numbers
• In• F• Rb• Sn• Ca• N• O
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
Lewis Symbols
shows valence electrons as dots arranged around atomic symbol.
The Octet Rule
Atoms tend to gain, lose, or share electrons until they have eight valence electrons.
Ionic BondsIonic Bonds
• TRANSFER (give away) of cation (positive ion) to an anion (negative ion).
• Occurs between metal and a nonmetal
• Have high melting points
• Dissolved ionic compounds conduct electricity
Ionic Bonds: One Big Greedy Thief Dog!
E l e c t r o n T r a n s f e r
L i t h i u m Neon
Lewis Structures (Ionic)Draw Lewis structures for:
HF:
H2O:
NH3:
CH4:
H F
H O H
H N HH
H C HH
H
COVALENT BONDINGCOVALENT BONDING
SHARING SHARING of electrons between two of electrons between two bonding atomsbonding atoms
form between 2 nonmetals or a form between 2 nonmetals or a nonmetal and hydrogennonmetal and hydrogen
Lewis Structures (Covalent)Draw Lewis structures for:
KF:
MgI:
K F
MgI
● ● ●
●●
● ●●
I● ●
●●
● ●●
●
Covalent or Ionic?
• Na and Cl• C and H• C and S• N and N• Ca and S• Fe and Cl
IONIC
IONIC
COVALENT
COVALENT
COVALENT
IONIC
first name is name of cation
last name has name of anion.
Anion names always end in “ide”
Add prefixes to indicate subscripts.
Only use mono- prefix with oxide.
Molecular Naming Rules
PREFIX mono-
di-
tri-
tetra-
penta-
hexa-
SUBSCRIPT1
2
3
4
5
6
Molecular Names
• CCl4
• N2O
• SF6
• carbon tetrachloride
• dinitrogen monoxide
• sulfur hexafluoride
Molecular Names Examples
phosphorus trichloride
dinitrogen pentoxide
dihydrogen monoxide
PCl3
N2O5
H2O
Molecular Formulas Examples