Bell Work• What charges will each of the

following have as ions?BrSMgBaI

AlSrNPB

Physical Science – Lecture 39

Bonding

Octet Rule

• All elements want 8 electrons in their outer shell.

• They want 8 valence electrons to be complete.• Elements want valence electrons equal to

noble gases (group 8A)

• Only exception – Hydrogen and Helium only want 2.

Becoming a Noble Gas

• Elements can lose or gain electrons to become “noble like”.

• Loss of electrons = cation (+ charge)• Gain of electrons = anion (- charge)

Cations

• Elements lose electrons to become positive• Positive charge comes from an abundance of

protons.• For every electron lost, elements becomes +1.

Anions

• Elements gain electrons to become negative• Negative charge comes from an abundance of

electrons.• For every electron gained, elements becomes

-1.

Two types of Bonding - 1

• Covalent – between two non-metals. They share electrons.

• Two non-metals will share electrons to make them both think that they have a full outer shell.

Bonding - Covalent

Forming Covalent Compounds

• When elements covalently bond, they are given special names to designate how many of each element is present.

Covalent Bonding

• Formed between two non-metals. • Neither atom is "strong" enough to steal

electrons from the other.• Instead, they share their electrons from outer

molecular orbit with others to feel complete (8).

Covalent Bonding

• Elements can form single bonds, double bonds, or triple bonds with other elements.

• Bonds are represented with line drawn between two elements.

Single Bond

• Two electrons are shared between elements

Double Bond

• Four electrons are shared between elements

Triple Bond

• Six electrons are shared between elements

Counting to 8

• Each pair of electrons (lone pair) counts as 2 electrons toward the total of 8 for the element they are attached to.

• Each covalent bond (line) counts as 2 electrons for each element they are attached to.

• Everyone still wants 8.

Types of Bonding - 2

• Ionic – between a metal and a non-metal or a cation and an anion. They steal or give away electrons to each other.

• A metal will give its electrons to a non-metal to have a completed octet in the octet below its valence shell (becoming a cation).

• A non-metal will take electrons from a metal to fulfill its outer valence shell (becoming an anion).

Lone Pairs

• Electrons not involved in the bond are called “lone pairs”.

• Lone pairs consist of two electrons.

Ionic Bonding

• Ionic bond - type of bond formed between cations and anions.

• Mostly formed between metals and non-metals.

• Non-metals are more electronegative and steal the metals electrons.

Bonding - Ionic

Ionic Bonding

•Na does not have 8 electrons in its outer shell, it has none. •It gave away electrons. It did not share.

Ionic Bonding

• Metals NEVER keep their electrons! • They always give them away to non-metals.• They NEVER share!

Forming Ionic Compounds

• Ionic compounds come from ions.• The charges cancel out

• The cation (positive charged element) is written first in the formula.

• The anion is always written second.

Examples

• Ca2+ and SO42-

• Br- and Na+

• K+ and O2-

Can 3 Cl form a Covalent bond with P?

• What type of bond will they form?• Do they have enough electrons to make them

each feel like they have 8?

What is the structure for Water?

What about C and four F?

What about Ca and 2 Cl?

What about 2 Cl?

What about O bonded to O?

Double Bonds

What about N bonded to N?

CH4

Practice

NH3

BaBr2

SH2

S2