e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- 1s 2s 2p 3s 3p Energy Sodium e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- It could GAIN seven electrons to become more stable. Or… Or it could LOSE one electron to become more stable. Ion Na + e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e-

Sodium will LOSE an electron.

e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- 1s 2s 2p 3s 3p Energy e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Chlorine It could gain ONE electron to become more stable. Or… Or it could lose SEVEN electrons to become more stable. e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e-

e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- 1s 2s 2p 3s 3p Energy e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Chlorine Gaining an electron would require the least amount of energy! e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Ion Cl -

Electrons in the outermost s and p orbitals These are the most reactive

e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- 1s 2s 2p 3s 3p Energy Sodium e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Has only ONE electron in its outermost s and p orbitals. Therefore, it has one valence electron.

e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- 1s 2s 2p 3s 3p Energy e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Chlorine e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Has SEVEN electrons in its outermost s and p orbitals. Therefore, it has seven valence electrons.

An easier way to draw the valence electrons is through…

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.

For example… Chlorine has a greater attraction for electrons than Sodium Electronegativity / Chlorine = catcher

Occur between metals and nonmetals Like Sodium and Chlorine or Potassium and Fluorine

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

FK

FK

FK

FK

FK

FK + _ Potassium (K + ) ion [cation] Fluoride (F - ) ion [anion] An ionic bond forms from the attraction between the positive K + ion and the negative F - ion

FK + _ An ionic bond forms from the attraction between the positive K + ion and the negative F - ion The compound potassium fluoride (KF) consists of potassium (K + ) ions and fluoride (F - ) ions

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

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

Occur between two nonmetals Like Hydrogen and Chlorine or Chlorine and Chlorine

In covalent 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!

Cl 2 Chlorine forms a covalent bond with itself

Cl How will two chlorine atoms react? Each chlorine atom wants to gain one electron to fill all of its seats.

Cl

The octet is achieved by each atom sharing the electron pair in the middle.

Cl Full 8 seats (octet) Full 8 seats (octet)

Cl The octet is achieved by each atom sharing the electron pair in the middle.

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 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 circle the electrons for each atom that completes their octets Single bonds are abbreviated with a dash

Cl circle the electrons for each atom that completes their octets This is the chlorine molecule Cl 2

Remember: Covalent bonds occur between two nonmetals! You know this… …and this. But you need to learn this!

O2O2 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?

OO

OO Each atom has two unpaired electrons

OO

OO

OO

OO

O O Both electron pairs are shared.

6 valence electrons plus 2 shared electrons = full octet O O

O O 6 valence electrons plus 2 shared electrons = full octet

Two bonding pairs, O O making a double bond.

O O = For convenience, the double bond can be shown as two dashes. O O

O O = This is the oxygen molecule, O 2

Polar Covalent Bond Shared electrons spend more time closer to one of the bonding atoms For example – H 2 0 Non-Polar Covalent Bond Shared electrons do not spend more time closer to one of the bonding atoms For example – 0 2

Shared electrons spend more time closer to one of the bonding atoms Oxygen H H H The probability distribution for shared electrons. The electrons spend more time near the oxygen atom.

Electronegativity is the power of an atom to attract electrons The higher the value, the more electronegative the element

Shared electrons do not spend more time closer to one of the bonding atoms Oxygen The probability distribution for shared electrons is shared by both. Oxygen

Pauling’s Electronegativity Scale H 2.1 He - Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Ne - Na 0.9 Mg 1.2 Al 1.5 Si 1.8 P 2.1 S 2.5 Cl 3.0 Ar - You should be writing these down!

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

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