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Welcome back!. Definitions Ion an atom that has gained or lost one or more electrons Cation a positively charged ion Anion a negatively charged ion. Energy Level Diagram. e -. e -. e -. e -. e -. e -. 3p. e -. e -. 3 s. Energy. e -. e -. e -. e -. e -. e -. 2p. Sodium.

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Definitions

Ion

an atom that has gained or lost one or more electrons

Cation

a positively charged ion

Anion

a negatively charged ion


Energy Level Diagram

e-

e-

e-

e-

e-

e-

3p

e-

e-

3s

Energy

e-

e-

e-

e-

e-

e-

2p

Sodium

Ion Na+

e-

e-

2s

It could GAIN seven electrons to become more stable. Or…

e-

e-

1s

Or it could LOSE one electron to become more stable.



Energy Level Diagram energy

e-

e-

e-

e-

e-

e-

3p

e-

e-

3s

Energy

e-

e-

e-

e-

e-

e-

2p

Chlorine

e-

e-

2s

It could gain ONE electron to become more stable. Or…

e-

e-

1s

Or it could lose SEVEN electrons to become more stable.


Energy Level Diagram energy

e-

e-

e-

e-

e-

e-

3p

e-

e-

3s

Energy

e-

e-

e-

e-

e-

e-

2p

e-

e-

Chlorine

Ion Cl-

2s

e-

e-

1s

Gaining an electron would require the least amount of energy!


Valence electrons energy

Electrons in the outermost

s and porbitals

These are the most reactive


Energy Level Diagram energy

3p

e-

3s

Energy

e-

e-

e-

e-

e-

e-

2p

e-

e-

Sodium

2s

Has only ONE electron in its outermost s and p orbitals. Therefore, it has one valence electron.

e-

e-

1s


Energy Level Diagram energy

e-

e-

e-

e-

e-

3p

e-

e-

3s

Energy

e-

e-

e-

e-

e-

e-

2p

e-

e-

Chlorine

2s

Has SEVEN electrons in its outermost s and p orbitals. Therefore, it has seven valence electrons.

e-

e-

1s



Sometimes atoms get together and one or more electrons jumps from one atom to another…

…this causes both atoms to have opposite charges (ions)…

…which then causes these ions to be attracted to each other.

Ionic Bond


For example… from one atom to another…

Chlorine has a greater attraction for electrons than Sodium

But why?

Electronegativity / Chlorine = catcher


Ionic bonds from one atom to another…

Occur between metals and nonmetals

Like Sodium and Chlorine

or

Potassium and Fluorine


K from one atom to another…

F

In an ionic bond, electrons are first lost or gained, resulting in the formation of ions.


K from one atom to another…

F


K from one atom to another…

F


K from one atom to another…

F


K from one atom to another…

F


K from one atom to another…

F


An ionic from one atom to another…bondforms from the attraction

between the positive K+ ion

and the negative F- ion

_

K

+

F

Potassium (K+) ion

[cation]

Fluoride (F-) ion

[anion]


An ionic from one atom to another…bondforms from the attraction

between the positive K+ ion

and the negative F- ion

_

K

+

F

The compoundpotassium fluoride (KF)

consists of potassium (K+) ions

and fluoride (F-) ions


Ionic Bonds from one atom to another…

Properties of Ionic Compounds

Electrons are exchanged

Ions are formed

Ions “stick together” magnetically to form compound

Formed between metals and nonmetals

Electronegativity difference >1.7

Cation + Anion = “salt”

Forms crystals (ordered arrangements of ions)

Conduct electricity when dissolved or melted

High melting/boiling points

Hard and brittle

Rarely burn

Formation is always exothermic


Covalent Bonds from one atom to another…

Properties of Covalent Compounds

Electrons are shared

No ions are formed

Formed between two nonmetals

Electronegativity difference is minimal

Low melting and boiling points

Typically soft and squishy

Usually do not dissolve in water as well as ionic compounds

Don’t conduct electricity

Sometimes burn


Covalent bonds from one atom to another…

Occur between two nonmetals

Like Hydrogen and Chlorine

or

Chlorine and Chlorine


In covalent from one atom to another…bonding, atoms still want to achieve the lowest energy level possible (which means filling up all eight of their valence seats.)

But rather than losing or gaining electrons, atoms now SHARE an electron pair.


Covalent bonds attempt to fill up all eight of their valence seats…

Just like noble gases!

All physical systems tends towards a configuration of lowest energy


Chlorine forms a seats…

covalent bond with

itself

Cl2


How seats…

will

two

chlorine

atoms

react?

Cl

Cl

Each chlorine atom wants to gain one electron to fill all of its seats.


Cl seats…

Cl


Cl seats…

Cl


Cl seats…

Cl


Cl seats…

Cl


Cl seats…

Cl

The octet is achieved by

each atom sharing the

electron pair in the middle.


Cl seats…

Cl

Full 8 seats

(octet)

Full 8 seats

(octet)


Cl seats…

Cl

The octet is achieved by

each atom sharing the

electron pair in the middle.


Cl seats…

Cl

This is the bonding pair

It is a single bonding pair

It is called a SINGLE BOND

Single bonds are abbreviated with a dash


Cl seats…

Cl

This is the bonding pair

It is a single bonding pair

It is called a SINGLE BOND

Single bonds are abbreviated with a dash


Cl seats…

Cl

circle the electrons for

each atom that completes

their octets

Single bonds are abbreviated with a dash


Cl seats…

Cl

This is the chlorine molecule

Cl2

circle the electrons for

each atom that completes

their octets


Covalent bonds seats…

You know this…

But you need to learn this!

…and this.

Remember: Covalent bonds occur between two nonmetals!


O seats…2

Oxygen can also form a covalent bond with itself.

But it needs to form two bonds since it is in Group 6A.

How can this be done?


O seats…

O


O seats…

O

Each atom has two unpaired electrons


O seats…

O


O seats…

O


O seats…

O


O seats…

O


O seats…

O

Both electron pairs are shared.


O seats…

O

6 valence electrons

plus 2 shared electrons

= full octet


O seats…

O

6 valence electrons

plus 2 shared electrons

= full octet


O seats…

O

Two bonding pairs,

making a doublebond.


O seats…

O

O

O

=

For convenience, the double bond

can be shown as two dashes.


O seats…

O

=

This is the oxygen molecule,

O2


Covalent bonds seats…

Two kinds…

  • Polar Covalent Bond

  • Shared electrons spend more time closer to one of the bonding atoms

  • For example – H20

  • Non-Polar Covalent Bond

  • Shared electrons do not spend more time closer to one of the bonding atoms

  • For example – 02


Polar covalent bonds seats…

  • Shared electrons spend more time closer to one of the bonding atoms

The electrons spend more time near the oxygen atom.

H

H

Oxygen

The probability distribution for shared electrons.


How can you tell if you have a polar or non-polar covalent bond?

ELECTRONEGATIVITY

Electronegativity is the power of an atom to attract electrons

The higher the value, the more electronegative the element



Non-polar covalent bonds bond?

  • Shared electrons do not spend more time closer to one of the bonding atoms

The probability distribution for shared electrons is shared by both.

Oxygen

Oxygen


Non-polar covalent bond bond?

If the electronegativity difference between the two nonmetals is less than 0.3

Polar covalent bond

If the electronegativity difference between the two nonmetals is 0.3-1.7


Review bond?

Ionic bond

  • Between a metal and nonmetal

  • Electrons are lost/gained and the resulting change in charge attracts the ions together

    Covalent bond

  • Between two nonmetals

  • Electrons are shared between the atoms

  • Polar/Non-polar

  • Ruled by electronegativity


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