formula unit

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Covalent Bonding: Learning to Cooperate. formula unit. describe a covalent bond state the differences covalent and ionic bonds explain the term molecule describe a diatomic molecule. Key Words. covalent compound covalent bond diatomic molecule. Covalent Compound: - PowerPoint PPT Presentation

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formula unit

Covalent Bonding:

Learning to Cooperate

• describe a covalent bond • state the differences covalent and ionic bonds• explain the term molecule • describe a diatomic molecule

Key Wordscovalent compoundcovalent bonddiatomic molecule

Covalent Compound:

Contains two or more NON-METAL atoms.

Formed by SHARING valence electrons to fill outer shell – octet rule.

· A molecule is the smallest unit of a covalent compound.

Non-metal + Non-metal = covalent bonding

Fluorine atom:9 p+

9 e-

F

Fluorine atom:9 p+

9 e-

F

F2

covalent compound

HH

Water H2O

1p

8p1p

O

A molecule has different properties than the atoms from which it is formed

Methane CH4

C

H

H

H

H

Ammonia NH3

NH

H

H

O

Atoms can share one pair of electrons, or two or three pairs.

S

In the end – electrons must be arranged so that each atom has 8 electrons around it.

Diatomic ElementsForming a Covalent Bond with Yourself

No new substance is formed - the covalent bond forms a molecule of only one type of atom.

Diatomic elements are unstable as single atoms.

HH

They form covalent bonds with a same atom to make a stable molecule.

H2

molecule

I H N Br O Cl F ave o ight r ever riends

Diatomic Elements:

2 2 2 2 2 2 2

Element Symbol Diatomic MoleculeIodine I I2 (solid)

Hydrogen H H2 (gas)

Nitrogen N N2 (gas)

Bromine Br Br2 (liquid)

Oxygen O O2 (gas)

Chlorine Cl Cl2 (gas)

Fluorine F F2 (gas)

OOO2

molecule (double bond)

F2

molecule(single bond)

FF

Covalent Bonding:

Naming and Writing

Same – covalent compounds are also named using the “ide” ending for last non-metal.

Different – covalent naming uses prefixes before the name of each element.

Prefixes show the number of atoms of that element in the formula for the molecule.

Diatomic Elements2

Step 1: first non-metal is named with a prefix to show the number of atoms.

We do not use “mono” for the first non-metal.

nitrogen oxide

N O

Step 2: second non-metal is named with a prefix AND with the “ide” ending.

di

2 4

tetradinitrogen tetroxide

PrefixNumber of

Atoms

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6

PrefixNumber of

Atoms

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6

sulfur oxide

SO

mono

3

trisulfur trioxide

carbon bromide

C Br

tri

3 6

hexa

tricarbon hexabromide

Writing formulas

Step 1: Write the symbol of each element.

Step 2: Use a subscript to show the number of each type of atom given by the prefix.

Do not reduce covalent formulas.

phosphorus oxide

P O di

2 5

penta

PrefixNumber of

Atoms

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6

nitrogen iodide

N I 3

triPrefix

Number of Atoms

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6carbon oxide

CO 2

di

silicon sulfide

Si S di

2 4

tetra

**Always identify a compound as ionic (m + nm) or covalent (nm + nm) before doing anything.

Prefixes are used in naming covalent compounds ONLY.

Criss-crossing is only used in ionic compounds.

DO NOT reduce covalent compounds.

IMPORTANT POINTS:

sulfur chlorideberyllium chloride

BeCl 2

Be

SCl

mono

2

di

metal non-metal non-metal non-metal

ionic covalent

Cl

Cl

+2

-

-

SCl

Cl

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