1.1.6

Representing Covalent Bonds

Test yourself on Representing Covalent Bonds

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Dot-and-Cross Diagrams

Dot-and-cross diagrams can be used to represent covalent bonds and to show the sharing of electron pairs.

Chlorine (Cl<sub>2</sub>)

Chlorine (Cl₂)

Each chlorine (Cl) atom begins with 7 electrons in its outer shell.
By sharing 1 pair of electrons in a single covalent bond, each Cl atom obtains a full outer shell with 8 electrons.

Water (H<sub>2</sub>O)

Water (H₂O)

Because oxygen has 6 electrons in its outer shell, it needs to have 2 extra electrons shared with it to get a full outer electron shell.
To do this, it forms a single covalent bond with 2 hydrogen atoms.

Double and triple bonds

Double and triple bonds

The earlier examples show single covalent bonds (1 shared pair of electrons between atoms), but it is also possible to form double (2 shared pairs) and even triple covalent bonds (3 shared pairs).
Double and triple bonds are normally stronger and require more energy to break.

Oxygen (O<sub>2</sub>)

Oxygen (O₂)

Each oxygen needs 2 electrons to get a full outer shell.
So, each oxygen atom shares 2 electrons with the other, leaving 2 pairs of electrons in the shared space between the atoms.
This is an example of a double covalent bond.

Representing Covalent Bonds

There are many ways of representing covalent bonds in a molecule. 4 ways of representing ammonia are shown below:

Dot-and-cross with shells

Dot-and-cross with shells

Dots represent the outer shell electrons of atoms of 1 element.
Crosses represent the outer shell electrons of atoms of the other element.
A limitation of this method is that it shows electrons differently for each atom, when they are actually exactly the same.

Dot-and-cross without shells

Dot-and-cross without shells

Dots represent the outer shell electrons of atoms of 1 element.
Crosses represent the outer shell electrons of atoms of the other element.

Ball-and-stick

Ball-and-stick

Balls represent atoms.
Sticks represent bonds between the atoms.
A limitation of this method is that atoms are much closer together than the diagram shows.

Lines

Lines

The atomic symbol represents the atom.
Lines between the atoms represent a covalent bond.

1

Principles of Science I

1.1

Structure & Bonding

1.1.1Atomic Model 1.1.2Electron Shells, Sub-Shells & Orbitals 1.1.3Ionic Bonding 1.1.4Representing Ionic Bonds 1.1.5Covalent Bonding 1.1.6Representing Covalent Bonds 1.1.7Metallic Bonding 1.1.8Intermolecular Forces 1.1.9Intermolecular Forces 2 1.1.10End of Topic Test - Bonding 1.1.11Relative Masses 1.1.12The Mole 1.1.13Molar Calculations 1.1.14Molar Calculations 2 1.1.15Empirical & Molecular Formulae 1.1.16Balanced Equations 1.1.17Percentage Yield 1.1.18End of Topic Test - Amount of Substance

1.2

Properties of Substances

1.2.1The Periodic Table 1.2.2Ionisation Energy 1.2.3Factors Affecting Ionisation Energies 1.2.4Trends of Ionisation 1.2.5Trends in the Periodic Table 1.2.6Polarity 1.2.7Metals & Non-Metals 1.2.8Alkali Metals 1.2.9Alkaline Earth Metals 1.2.10Reactivity of Alkaline Earth Metals 1.2.11Redox 1.2.12Transition Metals 1.2.13Redox Reactions of Transition Metals

1.3

Cell Structure & Function

1.3.1Introduction to Cells 1.3.2Prokaryotes 1.3.3Organelles of Eukaryotic Cells 1.3.4Organelles of Eukaryotic Cells 2 1.3.5Organelles in Plant Cells 1.3.6Microscopy 1.3.7End of Topic Test - Cell Structure

1.4

Cell Specialisation

1.4.1Cell Specialisation 1.4.2Blood Cells 1.4.3Plant Cells 1.4.4Gametes

1.5

Tissue Structure & Function

1.5.1Human Gas Exchange 1.5.2Blood Vessels 1.5.3Atherosclerosis 1.5.4Skeletal Muscle 1.5.5Slow & Fast Twitch Fibres 1.5.6Neurones 1.5.7Speed of Transmission 1.5.8Action Potentials 1.5.9End of Topic Test - Neurones & Action Potentials 1.5.10Synapses 1.5.11Types of Synapse 1.5.12Medical Application 1.5.13End of Topic Test - Synapses 1.5.14Chemical Brain Imbalances 1.5.15Effect of Drugs on the Brain

1.6

Working with Waves

1.6.1Progressive Waves 1.6.2Wave Speed & Phase Difference 1.6.3Longitudinal & Transverse Waves 1.6.4Stationary Waves 1.6.5Stationary Waves 2 1.6.6Applications of Stationary Waves 1.6.7Interference 1.6.8Diffraction 1.6.9Diffraction Gratings 1.6.10Application of Diffraction Gratings

1.7

Waves in Communication

1.7.1Refraction at a Plane Surface 1.7.2Internal Reflection & Fibre Optics 1.7.3Applications of Total Internal Reflection 1.7.4Properties 1.7.5Gamma, X-Ray & UV Light 1.7.6Visible Light 1.7.7Infrared, Microwave & Radio Waves 1.7.8Intensity 1.7.9Digital & Analogue Signals 1.7.10Communication Channels

2

Practical Scientific Procedures and Techniques

2.1

Titration

2.1.1pH Curves & Titrations 2.1.2pH Curves & Titrations 2 2.1.3Buffer Solutions

2.2

Colorimetry

2.2.1Measuring Rates 2.2.2Beer-Lambert Law

2.3

Chromatography

2.3.1Overview of Chromatography 2.3.2Thin-Layer Chromatography 2.3.3Column Chromatography 2.3.4Gas Chromatography

3

Science Investigation Skills

3.1

Scientific Processes

3.1.1Aims, Hypotheses & Sampling 3.1.2Pilot Studies & Design 3.1.3Ethics 3.1.4Variables & Control 3.1.5Demand Characteristics & Investigator Effects 3.1.6Features of Science 3.1.7Scientific Report 3.1.8Scientific Report 2

3.2

Data Handling & Analysis

3.2.1Types of Data 3.2.2Descriptive Statistics 3.2.3Presentation & Display of Data

3.3

Enzymes in Action

3.3.1Overview of Protein Structure 3.3.2Enzymes 3.3.3Factors Affecting Enzyme Activity 3.3.4Enzyme-Controlled Reactions

3.4

Diffusion

3.5

Plants & Their Environment

3.5.1Factors Affecting Plant Growth 3.5.2Measuring Number & Distribution of Species

3.6

Energy Content in Fuels

3.6.1Fractions 3.6.2Burning Hydrocarbons 3.6.3Combustion 3.6.4Energy 3.6.5Energy at Home 3.6.6Calorimetry

3.7

Electrical Circuits

3.7.1Circuit Diagrams & Components 3.7.2Diodes, LDRs & Thermistors 3.7.3Resistance 3.7.4Electrical Work 3.7.5Ohm's Law 3.7.6Domestic Uses of Electricity 3.7.7Fuses

4

Principles of Science II

4.1

Extracting Elements

4.1.1Atom Economy

4.2

Relating Properties to use of Substances

4.2.1Group 2 Chemistry 4.2.2End of Topic Test - Group 2 4.2.3Electrolysis 4.2.4Electrolysis Examples 4.2.5Extracting Metals 4.2.6Transition Metals 4.2.7Variable Oxidation States 4.2.8Heterogeneous Catalysts 4.2.9Homogeneous Catalysts

4.3

Organic Chemistry

4.3.1Naming Compounds 4.3.2Functional Groups 4.3.3Isomerism 4.3.4Hydrocarbons 4.3.5Structure of Alkanes 4.3.6Boiling Points of Alkanes 4.3.7Alkenes 4.3.8Curly Arrows & Mechanisms 4.3.9Cracking 4.3.10Combustion 4.3.11Free Radical Substitution of Alkanes 4.3.12Electrophilic Addition of Alkenes

4.4

Energy Changes in Industry

4.4.1The Kelvin Scale 4.4.2Enthalpy Changes 4.4.3Calorimetry 4.4.4Bond Enthalpies 4.4.5Hess' Law

4.5

The Circulatory System

4.5.1The Circulatory System 4.5.2Blood Vessels 4.5.3Blood Transfusion & the ABO Rhesus System 4.5.4The Heart 4.5.5The Cardiac Cycle 4.5.6Cardiac Output 4.5.7Coordination of Heart Action 4.5.8Heart Dissection 4.5.9Controlling Heart Rate 4.5.10Electrocardiograms 4.5.11Cardiovascular Disease 4.5.12Investigating Heart Rates

4.6

Ventilation & Gas Exchange

4.6.1Human Gas Exchange 4.6.2Ventilation 4.6.3Measuring Gas Exchange 4.6.4Controlling Ventilation Rate 4.6.5Lung Disease 4.6.6Lung Disease Data

4.7

Urinary System

4.7.1Kidneys & Control of Water Balance 4.7.2Kidneys & Osmoregulation 4.7.3Kidneys & Blood Pressure 4.7.4Urine 4.7.5Kidney Failure & Urinalysis 4.7.6Dialysis 4.7.7Transplants

4.8

Cell Transport

4.8.1Cell Membrane Structure 4.8.2Diffusion 4.8.3Osmosis 4.8.4Active Transport

4.9

Thermal Physics

4.9.1Power & Efficiency 4.9.2Work & Energy 4.9.3Conservation of Energy 4.9.4Pressure 4.9.5First Law of Thermodynamics 4.9.6Second Law of Thermodynamics 4.9.7Heat Engines, Heat Pumps & Refrigerators 4.9.8Non-Flow Processes 4.9.9p-V Diagrams 4.9.10Ideal Gases 4.9.11Ideal Gases 2 4.9.12Thermal Energy Transfer 4.9.13Thermal Energy Transfer Experiments

4.10

Materials

4.10.1Density 4.10.2Stress & Strain 4.10.3Properties of Materials 4.10.4Elasticity 4.10.5Plasticity 4.10.6Energy in Materials 4.10.7Young Modulus

4.11

Fluids

4.11.1Fluid Flow 4.11.2Viscosity 4.11.3Density 4.11.4Continuity Equation 4.11.5Bernoulli's Equation 4.11.6Non-Newtonian Fluids

5

Contemporary Issues in Science

5.1

Contemporary Issues in Science

5.1.1Sustainability 5.1.2Genetic Engineering 5.1.3Uses of Genetic Modification 5.1.4Stem Cell Therapy 5.1.5Cloning 5.1.6Cloning 2 5.1.7Nanotechnology 5.1.8Ecosystems

5.2

Analysing Scientific Information

5.2.1Validity 5.2.2Peer Review

Jump to other topics

1

Principles of Science I

1.1

Structure & Bonding

1.1.1Atomic Model 1.1.2Electron Shells, Sub-Shells & Orbitals 1.1.3Ionic Bonding 1.1.4Representing Ionic Bonds 1.1.5Covalent Bonding 1.1.6Representing Covalent Bonds 1.1.7Metallic Bonding 1.1.8Intermolecular Forces 1.1.9Intermolecular Forces 2 1.1.10End of Topic Test - Bonding 1.1.11Relative Masses 1.1.12The Mole 1.1.13Molar Calculations 1.1.14Molar Calculations 2 1.1.15Empirical & Molecular Formulae 1.1.16Balanced Equations 1.1.17Percentage Yield 1.1.18End of Topic Test - Amount of Substance

1.2

Properties of Substances

1.2.1The Periodic Table 1.2.2Ionisation Energy 1.2.3Factors Affecting Ionisation Energies 1.2.4Trends of Ionisation 1.2.5Trends in the Periodic Table 1.2.6Polarity 1.2.7Metals & Non-Metals 1.2.8Alkali Metals 1.2.9Alkaline Earth Metals 1.2.10Reactivity of Alkaline Earth Metals 1.2.11Redox 1.2.12Transition Metals 1.2.13Redox Reactions of Transition Metals

1.3

Cell Structure & Function

1.3.1Introduction to Cells 1.3.2Prokaryotes 1.3.3Organelles of Eukaryotic Cells 1.3.4Organelles of Eukaryotic Cells 2 1.3.5Organelles in Plant Cells 1.3.6Microscopy 1.3.7End of Topic Test - Cell Structure

1.4

Cell Specialisation

1.4.1Cell Specialisation 1.4.2Blood Cells 1.4.3Plant Cells 1.4.4Gametes

1.5

Tissue Structure & Function

1.5.1Human Gas Exchange 1.5.2Blood Vessels 1.5.3Atherosclerosis 1.5.4Skeletal Muscle 1.5.5Slow & Fast Twitch Fibres 1.5.6Neurones 1.5.7Speed of Transmission 1.5.8Action Potentials 1.5.9End of Topic Test - Neurones & Action Potentials 1.5.10Synapses 1.5.11Types of Synapse 1.5.12Medical Application 1.5.13End of Topic Test - Synapses 1.5.14Chemical Brain Imbalances 1.5.15Effect of Drugs on the Brain

1.6

Working with Waves

1.6.1Progressive Waves 1.6.2Wave Speed & Phase Difference 1.6.3Longitudinal & Transverse Waves 1.6.4Stationary Waves 1.6.5Stationary Waves 2 1.6.6Applications of Stationary Waves 1.6.7Interference 1.6.8Diffraction 1.6.9Diffraction Gratings 1.6.10Application of Diffraction Gratings

1.7

Waves in Communication

1.7.1Refraction at a Plane Surface 1.7.2Internal Reflection & Fibre Optics 1.7.3Applications of Total Internal Reflection 1.7.4Properties 1.7.5Gamma, X-Ray & UV Light 1.7.6Visible Light 1.7.7Infrared, Microwave & Radio Waves 1.7.8Intensity 1.7.9Digital & Analogue Signals 1.7.10Communication Channels

2

Practical Scientific Procedures and Techniques

2.1

Titration

2.1.1pH Curves & Titrations 2.1.2pH Curves & Titrations 2 2.1.3Buffer Solutions

2.2

Colorimetry

2.2.1Measuring Rates 2.2.2Beer-Lambert Law

2.3

Chromatography

2.3.1Overview of Chromatography 2.3.2Thin-Layer Chromatography 2.3.3Column Chromatography 2.3.4Gas Chromatography

3

Science Investigation Skills

3.1

Scientific Processes

3.1.1Aims, Hypotheses & Sampling 3.1.2Pilot Studies & Design 3.1.3Ethics 3.1.4Variables & Control 3.1.5Demand Characteristics & Investigator Effects 3.1.6Features of Science 3.1.7Scientific Report 3.1.8Scientific Report 2

3.2

Data Handling & Analysis

3.2.1Types of Data 3.2.2Descriptive Statistics 3.2.3Presentation & Display of Data

3.3

Enzymes in Action

3.3.1Overview of Protein Structure 3.3.2Enzymes 3.3.3Factors Affecting Enzyme Activity 3.3.4Enzyme-Controlled Reactions

3.4

Diffusion

3.5

Plants & Their Environment

3.5.1Factors Affecting Plant Growth 3.5.2Measuring Number & Distribution of Species

3.6

Energy Content in Fuels

3.6.1Fractions 3.6.2Burning Hydrocarbons 3.6.3Combustion 3.6.4Energy 3.6.5Energy at Home 3.6.6Calorimetry

3.7

Electrical Circuits

3.7.1Circuit Diagrams & Components 3.7.2Diodes, LDRs & Thermistors 3.7.3Resistance 3.7.4Electrical Work 3.7.5Ohm's Law 3.7.6Domestic Uses of Electricity 3.7.7Fuses

4

Principles of Science II

4.1

Extracting Elements

4.1.1Atom Economy

4.2

Relating Properties to use of Substances

4.2.1Group 2 Chemistry 4.2.2End of Topic Test - Group 2 4.2.3Electrolysis 4.2.4Electrolysis Examples 4.2.5Extracting Metals 4.2.6Transition Metals 4.2.7Variable Oxidation States 4.2.8Heterogeneous Catalysts 4.2.9Homogeneous Catalysts

4.3

Organic Chemistry

4.3.1Naming Compounds 4.3.2Functional Groups 4.3.3Isomerism 4.3.4Hydrocarbons 4.3.5Structure of Alkanes 4.3.6Boiling Points of Alkanes 4.3.7Alkenes 4.3.8Curly Arrows & Mechanisms 4.3.9Cracking 4.3.10Combustion 4.3.11Free Radical Substitution of Alkanes 4.3.12Electrophilic Addition of Alkenes

4.4

Energy Changes in Industry

4.4.1The Kelvin Scale 4.4.2Enthalpy Changes 4.4.3Calorimetry 4.4.4Bond Enthalpies 4.4.5Hess' Law

4.5

The Circulatory System

4.5.1The Circulatory System 4.5.2Blood Vessels 4.5.3Blood Transfusion & the ABO Rhesus System 4.5.4The Heart 4.5.5The Cardiac Cycle 4.5.6Cardiac Output 4.5.7Coordination of Heart Action 4.5.8Heart Dissection 4.5.9Controlling Heart Rate 4.5.10Electrocardiograms 4.5.11Cardiovascular Disease 4.5.12Investigating Heart Rates

4.6

Ventilation & Gas Exchange

4.6.1Human Gas Exchange 4.6.2Ventilation 4.6.3Measuring Gas Exchange 4.6.4Controlling Ventilation Rate 4.6.5Lung Disease 4.6.6Lung Disease Data

4.7

Urinary System

4.7.1Kidneys & Control of Water Balance 4.7.2Kidneys & Osmoregulation 4.7.3Kidneys & Blood Pressure 4.7.4Urine 4.7.5Kidney Failure & Urinalysis 4.7.6Dialysis 4.7.7Transplants

4.8

Cell Transport

4.8.1Cell Membrane Structure 4.8.2Diffusion 4.8.3Osmosis 4.8.4Active Transport

4.9

Thermal Physics

4.9.1Power & Efficiency 4.9.2Work & Energy 4.9.3Conservation of Energy 4.9.4Pressure 4.9.5First Law of Thermodynamics 4.9.6Second Law of Thermodynamics 4.9.7Heat Engines, Heat Pumps & Refrigerators 4.9.8Non-Flow Processes 4.9.9p-V Diagrams 4.9.10Ideal Gases 4.9.11Ideal Gases 2 4.9.12Thermal Energy Transfer 4.9.13Thermal Energy Transfer Experiments

4.10

Materials

4.10.1Density 4.10.2Stress & Strain 4.10.3Properties of Materials 4.10.4Elasticity 4.10.5Plasticity 4.10.6Energy in Materials 4.10.7Young Modulus

4.11

Fluids

4.11.1Fluid Flow 4.11.2Viscosity 4.11.3Density 4.11.4Continuity Equation 4.11.5Bernoulli's Equation 4.11.6Non-Newtonian Fluids

5

Contemporary Issues in Science

5.1

Contemporary Issues in Science

5.1.1Sustainability 5.1.2Genetic Engineering 5.1.3Uses of Genetic Modification 5.1.4Stem Cell Therapy 5.1.5Cloning 5.1.6Cloning 2 5.1.7Nanotechnology 5.1.8Ecosystems

5.2

Analysing Scientific Information

5.2.1Validity 5.2.2Peer Review

Practice questions on Representing Covalent Bonds

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1
Nitrogen atoms have 5 electrons in their outer shell. What type of bond forms between 2 nitrogen atoms?Multiple choice
2
When compared with single covalent bonds, double and triple covalent bonds...True / false
3
Which of the following is NOT a way of representing covalent bonds?Multiple choice

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Covalent Bonding

Metallic Bonding