Ionic BondingChapter 6

Quick Review

• Atomic number = Total number of electrons

• The group number tells you the amount of valence electrons an element has.

• The metals are on the left side of the periodic table

• The nonmetals are on the right side of the periodic table.

• All elements need 8 electrons in their outer shell to be stable. (Except H and He, they only need 2)

Valence Electrons

• Valence Electron- Any electron that is in the outermost energy level of an atom.

• When the outer most (highest) energy level is full the atom is stable. It will most likely not react

• What family (group) is least reactive? Why?

How many valence electrons?

• List the number of valence electrons for the following elements:• 1. Potassium__________________

• 2. Silicon ____________________

• 3. Oxygen____________________

• 4. Boron______________________

• 5. Helium_____________________

Electron Dot Diagrams

• Also called Lewis Structures

• The “dots” represent the valence electrons

• Element symbol represents the nucleus and inner electrons

Steps for drawing dot diagrams

• 1. Figure out the number of valence electrons by looking at the periodic table.

• 2. Write the element symbol

• 3. Put the dots around the symbol (dots= valence electrons) * start at the top and work clockwise just like the Bohr atom models.

• ** Remember: each space must be filed with 1 electron before they can double up.

Examples

• Calcium

• Sulfur

• Neon

• Remember the Rules

• 1. Figure out the number of valence electrons by looking at the periodic table.

• 2. Write the element symbol

• 3. Put the dots around the symbol (dots= valence electrons) * start at the top and work clockwise just like the Bohr atom models.

• ** Remember: each space must be filed with 1 electron before they can double up.

Ion Formation

• Elements that do not have a full outer shell react with other elements to become more stable.

• OCTET RULE- atoms want 8 valence electrons in their outermost energy level

• Elements follow this rule by losing or gaining valence electrons (donating or accepting electrons)

• When this happens the number of protons and electrons are NOT EQUAL anymore. Atoms are no longer overall neutral.

ion

•Ion- an atom that has a negative or positive charge due to losing or gaining an electron.

Lose or gain?Element Gain or lose

electrons?How many electrons need to be lost or gained?

Potassium (K)

Silicon (Si)

Oxygen (O)

Boron (B)

Hydrogen (H)

Carbon (C)

Nitrogen (N)

H would like to C would like toN would like toO would like to

Gain 4 electrons

Gain 1 electron

Gain 3 electrons

Gain 2 electrons

Ionic Bond

• Bond formed between 2 elements by the TRANSFER of electrons

• It’s between a METAL and NONMETAL• Metals= Lose electrons• Nonmetal= Gain electrons

• The force that holds ions together.

How to draw an ionic bond!!!!

• 1. Write out the symbols for the elements you are trying to bond.

• 2. Draw the Dot Diagram

• 3. Determine which element is the metal and which one is the nonmetal (Which one is going to lose/gain electrons)

Drawing ionic bonds

• Show the transfer of electrons using arrows

• Na + Cl Na+ Cl-

1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

If an atom loses electrons:• It becomes a positive ion = CATION• These are elements that have 3 or less

valence electrons• Elements that have 4 valence electrons

can become cations or anions depending on the situation!

If an atom gains electrons:• It becomes a negative ion = ANION• To name an anion, change the element’s

name to have “ide” at the end• These are elements that have 5 or more

valence electrons

Formation of Ions from Metals

• Ionic compounds result when metals react with nonmetals

• Metals lose electrons to gain a full outer electron shell (the next electron shell becomes the new outer shell)

• Positive ions form when electrons are lost

Group 1A metals ion +1

Group 2A metals ion +2

Group 3A metals ion +3

Formation of Ions from Nonmetals

• Nonmetals gain electrons to gain a full outer electron shell

• Negative ions form when electrons are gained

Group 5A nonmetals ion -3

Group 6A nonmetals ion -2

Group 7A nonmetals ion -1

• Group 8A elements do not gain or lose electrons since they already have a full outer shell.

The formation of sodium chloride (salt)

Properties of Ionic Compounds

1. Individual atoms are bound tightly together forming crystal structures

2. High melting points

3. High boiling points

4. Conduct electricity when melted or in solution

5. Many can be dissolved in water