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 of electrons from one bonding atom to another

• Occurs when electron transfers from a metal to a nonmetal

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 of electrons between two bonding atoms

Occurs when electron shares Occurs when electron shares between nonmetals

Lewis Structures (Covalent)Draw Lewis structures for:

KF:

MgI:

K F

MgI

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