Molecular ModelsMolecular ModelsChemistry Lab Work

Theme and Aim of the WorkTheme and Aim of the Work

To construct molecules of compounds To construct models of crystal structures

Materials: student molecular model set

Ball-and-stick model

Framework model

Space-filling model

Types of Molecular ModelsTypes of Molecular Models

•Single bond•Double bond•Triple bond

Student Molecular Model SetStudent Molecular Model Set

Types of Chemical BondsTypes of Chemical Bonds

Representation of AtomsRepresentation of Atoms

Carbon

Oxygen

Chlorine (Halogens)

Metals

Hydrogen

Nitrogen

Sulphur

Linear

Bent

Trigonal planar

Types of Molecular StructuresTypes of Molecular Structures

• Square planar

• Tetrahedral

• Octahedral

Chemical Bonding

Ionic bondingElectrons are completely transferred from one atom to another.

Covalent bondingAtoms share electrons.

What is a covalent bond?What is a covalent bond?

A covalent bond is formed when atoms share valence electrons.

H + H H - H

What is a covalent bond?What is a covalent bond?

What is the difference between What is the difference between a a singlesingle covalent bond covalent bond and and a a multiple multiple covalent covalent bond?bond?

A single bond means that only one electron pair is shared between two atoms.

A double bond means that two electron pairs are shared.

A triple bond means that three electron pairs are shared.

H + H H - H

O = O

N N

What is the difference between What is the difference between a a singlesingle covalent bond covalent bond and and a a multiple multiple covalent covalent bond?bond?

What compound is it?

Ammonia

NH3

What compound is it?

What compound is it?

Carbon dioxide

CO2

What compound is it?

What compound is it?

Hydrogen chloride

HCl

What compound is it?

What compound is it?

Water

H2O

What compound is it?

What compound is it?

Hydrogen sulphide

H2S

What compound is it?

What is incorrect?

What is incorrect?

Why?

Wrong bonding

Bounds should be single, the molecular structure should be bent.

Why are the models incorrect?

Correct

The molecular structure should be linear

The bond should be double.

Crystal ModelsCrystal Models

What is characteristic for What is characteristic for crystals with covalent bonds?crystals with covalent bonds?

Crystals are usually hard and brittle. Their melting point is high. Covalent substances are insoluble in water.

Example : diamond

What is characteristic for What is characteristic for crystals with covalent bonds?crystals with covalent bonds?

How to construct a diamond model:How to construct a diamond model:

We use models of carbon atom with four bonds

(tetrahedral). models of single bonds.

What is characteristic for What is characteristic for crystals with ionic bonds?crystals with ionic bonds?

Example : NaCl

What is characteristic for What is characteristic for crystals with ionic bonds?crystals with ionic bonds?

Crystals are usually brittle. Their melting point is high. Ionic substances are soluble in water.

How to construct a NaCl model:How to construct a NaCl model:

We use models of Na+ ions. models of Cl- ions. models of single bonds.

The Ionic Crystal Model The Ionic Crystal Model of Sodium Chloride(NaCl)of Sodium Chloride(NaCl)

G a SOSPg Znojmo, Czech R.

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