Chemical Bonds J. E. Odom 2014. Compounds and Chemical Formulas Compound – Two or more elements chemically combined Chemical Formula – Chemical “short.

Chemical Bonds

J. E. Odom2014

Compounds and Chemical Formulas

Compound– Two or more elements

chemically combined

Chemical Formula– Chemical “short hand”– Shows what ELEMENTS a

compound contains– Shows HOW MANY ATOMS

of each element

H2O

C6H12O6

2 atoms of Hydrogen1 atom of Oxygen

6 atoms of Carbon12 atom of Hydrogen6 atoms of Oxygen

Common Chemical Compounds

Can you tell what elements are present and HOW MANY atoms of each element are present in each compound?

Why do elements form compounds?– All atoms want a full outer

electron shell – FULL Outer Shell = stable

atom (less reactive)

EXAMPLES:• H and He need 2 electrons to

become Full/stable• Groups 1 – 18 need at least 8

electrons to be full/stable

VALENCE ELECTRONS = Electrons in the outermost shell of an atom

Chemical Bonds

ATOMS WILL FORM BONDS in order to fill the outer electron shell…to become more stable

Chemical Bond = Attraction between atoms when electrons are gained, lost or shared

2 types of bonds• Ionic• Covalent

What happens when an atom Gains or Loses an electron just to be stable?

The atoms become IONS(Charged particles)

IONSATOM Loses electron (-)BECOMES MORE POSITIVE

ATOM Gains electron (-) BECOMES MORE NEGATIVE

The + or – Charge of the ion is equal to the NUMBER of electrons

lost or gained

PRACTICEFor each of the following compounds, LIST the elements present AND the number of atoms of each element

1)

2)

3)

4)

5)

6)

7)

8)

9)

10)

For each of the following elements, state the VALENCE electrons.

11) Nitrogen (N)

12) Hydrogen (H)

13) Potassium (K)

14) Calcium (Ca)

15) Carbon (C)

16) Argon (Ar)

17) Aluminum (Al)

18) Silicon (Si)

19) Lithium (Li)

20) Beryllium (Be)

In your notebook, write the problem and the solution

For each of the following atoms, write the NEW ION that is formed AND its charge

21) Calcium loses 2 e-

22) Sodium loses 1 e-

23) Chlorine gains 1 e-

24) Lithium loses 1 e-

25) Magnesium loses 2 e-

26) Bromine gains 1 e-

27) Aluminum loses 3 e-

28) Sulfur gains 2 e-

29) Iron loses 2 e-

30) Potassium gains 3 e-

Lewis Dot StructureStructure that shows the valence electrons for a given atom; helps predict how one atom might combine with another atom to form a compound.

PRACTICE ELEMENT Chemical Symbol

Total number of Electrons

Valence Electrons

Dot Diagram

Potassium K

Nitrogen N

Carbon C

Beryllium Be

Neon Ne

Sulfur S

NOW…Try to predict the chemical formulas

Elements Dot Diagram for EACH Element

Dot Diagram for Compound

Chemical Formula

Na and F

Br and Br

Mg and O

Complete the following tables in

your notebook

Day 2 Ionic & Covalent Bonds

IONIC BONDS

– Force of attraction between opposite charged ions

– Form between METALS & Non-metals

Ionic Compounds

IONS ARE FORMED+Cation– Metals– Lose electrons– Carry a (+) oxidation

number

-Anion– Nonmetals– Gain electrons– Carry a (-) oxidation

number

Oxidation NumberNumber of electrons gained, lost or shared to become stable(NEGATIVE means that electrons will be gained;POSITIVE means that electrons will be given away)

THIS IS NOT VALENCERECOGNIZE THE DIFFERENCE???

Using RED pen/pencil Write the Oxidation Number for each group on the chart.

Covalent Bonds– Attraction between atoms when

they share electrons

– Sharing occurs between 2 or more NON-METALS

– Can have equal or unequal sharing

– Equal sharing = no charge or neutral compound also called Non-Polar

– Unequal sharing = POLAR MOLECULE (EX: Water)

Covalent Bonds

PRACTICE

Before moving forward students must understand…1. What are Valence Electrons2. How to complete an Electron dot diagram for an

element3. How to create an electron dot diagram for a

compound4. Difference between Ionic and Covalent bonds5. How to find the oxidation number for a given

element

STEPS TO Create compounds from combinations of elements:

1) Are the elements METALS or NON-METALS (This determines

whether they will form ionic or covalent bonds)

2) What is the Valence

3) What will the Element need to fill its outermost shell?

4) Will you need additional atoms of the element to satisfy the

outermost shell requirements; if so, how many?

5) Draw the Electron Dot Diagram showing either transferred

electrons or shared electrons.

6) What is the chemical formula for the compound?

Writing & Naming Compounds

Writing & Naming Compounds

BINARY compound is a compound composed of two elements

REMEMBER: Oxidation number tells us how many electrons an atom has Lost, Gained, or shared to become stable.

Ionic Compounds: elements themselves become ions

Ions have a charge, but the net charge of the compound is ZERO.

Binary Ionic CompoundsComposed of only two elementsIONIC: Metal + Non-metal

Shortcut to Writing Binary Ionic Compounds

1. Write oxidation numbers above symbols

2. Criss-cross oxidation numbers writing them as subscripts (small numbers at the

bottom right of the element)

3. The metal is ALWAYS written first

4. Will always be between (+) and (-) ions

PRACTICE:

Metal Cation(+) NonMetal Anion (-) Compound Formula

Sodium Na+1 Oxygen O-2 Na2O

Aluminum Sulfur

Magnesium Phosphorus

Potassium Selenium

Naming Binary Ionic Compounds

1. Write the name of the metal/cation first

2. Drop the end of the nonmetal

3. Add “ide” to the nonmetal

Practice NAMING Binary Ionic Compounds

Metal Cation(+) NonMetal Anion (-) Compound Formula

Compound Name

Sodium Na+1 Oxygen O-2 Na2OSodium oxide

Aluminum Al+3 Sulfur S-2 Al2S3Aluminum

sulfide

Magnesium Mg+2 Phosphorus P-3 Mg3P2Magnesium phosphide

Potassium K+1 Selenium Se-2 K2Se Potassium selenide

Writing Covalent Compounds

– Add prefixes to show HOW MANY atoms of each element are in the compound

– Compound Ends in -ide

PRACTICE

Polyatomic Ions

Polyatomic Ions

• Polyatomic Ions– Positively or negatively

charged– Covalently bonded– Contains two or more

atoms

Polyatomic Ions to Know . . . .Charge Name Formula

1 + Ammonium NH₄

1 - Acetate

Chlorate

Hydroxide

Nitrate

C₂H₃O₂

ClO₃

OH

NO₃

2 - Carbonate

Sulfate

CO₃

SO₄

3 – Phosphate PO₄

POLYATOMIC IONS• Positive or Negative

Compounds• COVALENT Bonds

(sharing electrons)• Contain 2 or MORE atoms

Writing Formulas Examples

• Calcium Nitride

• Carbon Trioxide

• Sodium Nitrate

• Potassium Hydroxide

• Magnesium Oxide

• Sulfur Diphosphide

• Aluminum Sulfate

• Ammonium Phosphate