Molecules

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Molecules

Molecules are formed when two or more atoms join together chemically. Different types of bonds form to chemically join different elements.

Covalent bonds

Covalent bonds are bonds between non-metals and non-metals.
Covalent bonding is the sharing of electrons in the outer shell of the atoms.
Sometimes atoms can share two or three pairs with each other.
The bonding is strong between covalent bonds.

Molecules

Molecules are two or more atoms joined together by strong covalent bonds.
The intermolecular forces between the atoms however are weak.
Atoms in molecules are always joined together by covalent bonds.

Properties of molecules joined by covalent bonds

They tend to have low boiling points.
They tend to have low melting points.
They are often poor electrical conductors.
They are often poor thermal conductors.

Diatomic atoms

Two atoms covalently bonded together are called diatomic.
- Group 7 atoms will form single bonds (Cl2).
- Group 6 atoms will form double bonds (O2).
- Group 5 atoms will form triple bonds (N2).

Examples of molecules with covalent bonds

Other examples of molecules include:
- Water H2O
- Hydrochloric Acid HCl
- Carbon Dioxide CO2
- Sulfur Dioxide SO2

Biology

1.1

Cells, Tissues & Organs

1.1.1Microscopes 1.1.2Magnification 1.1.3Multicellular Organisms 1.1.4Tissues 1.1.5Organs 1.1.6Unicellular Organisms 1.1.7Diffusion 1.1.8Factors Affecting Diffusion 1.1.9Plant Cells 1.1.10Cellulose 1.1.11Plant Tissues 1.1.12Leaves 1.1.13Animal Cells 1.1.14Comparing Animal & Plant Cells 1.1.15How to Make a Model Animal and Plant Cell 1.1.16Specialised Cells 1.1.17Stem Cells 1.1.18Uses of Stem Cells 1.1.19Disadvantages of Stem Cells 1.1.20Blood Components 1.1.21Platelets 1.1.22The Lungs 1.1.23Breathing 1.1.24Plant Gas Exchange 1.1.25Drugs 1.1.26Diagnostic Misconceptions - Microbes 1.1.27Diagnostic Misconceptions - Diff. vs Specialised 1.1.28Diagnostic Misconceptions - Types of Cell 1.1.29Diagnostic Misconceptions - Plants & Animal Cells 1.1.30End of Topic Test - Magnification & Cells 1.1.31End of Topic Test - Cells & Organisation 1.1.32End of Topic Test - Living Organisms

1.2

Reproduction & Variation

1.3

Ecological Relationships & Classification

1.3.1Species Interdependence 1.3.2Food Chains & Webs 1.3.3Changes to Food Webs - Plants 1.3.4Changes to Food Webs - Animals 1.3.5Changes to Food Webs - Factors 1.3.6Relationships in an Ecosystem 1.3.7The Impact of Environmental Change 1.3.8Decomposers 1.3.9Decay 1.3.10Assessing Ecosystems 1.3.11Ecological Sampling - Quadrats 1.3.12Ecological Sampling 1.3.13Required Practical - Estimating Population Size 1.3.14Pyramids of Number and Biomass 1.3.15Classification of Living Organisms 1.3.16Competition Between Organisms 1.3.17Adaptations of Plants 1.3.18Natural Selection 1.3.19Evidence for Evolution 1.3.20Environmental Changes & Extinctions 1.3.21The Importance of Biodiversity 1.3.22Bioaccumulation 1.3.23Bioaccumulation - DDT and Mercury 1.3.24End of Topic Test - Food Webs 1.3.25End of Topic Test - Material Cycles & Energy 1.3.26End of Topic Test - Population & Evolution

1.4

Digestion & Nutrition

1.4.1Balanced Diets 1.4.2Vitamins & Minerals 1.4.3Protein 1.4.4Lipids, Oils and Fats 1.4.5Carbohydrates 1.4.6Starch 1.4.7Energy Needs 1.4.8Dietary Fibre 1.4.9Diseases Caused by Nutritional Deficiencies 1.4.10Digestion 1.4.11Enzymes in Digestion 1.4.12Required Practical - Enzymes in Digestion 1.4.13Plant Nutrition 1.4.14Diagnostic Misconceptions - Digestion 1.4.15Diagnostic Misconceptions - Excretion vs Egestion 1.4.16End of Topic Test - Nutrition

1.5

Plants & Photosynthesis

1.5.1Roots 1.5.2Photosynthesis 1.5.3Leaves in Photosynthesis 1.5.4Rate of Photosynthesis 1.5.5Testing the Rate of Photosynthesis 1.5.6Water Transport in Plants 1.5.7Translocation 1.5.8The Carbon Cycle 1.5.9Human Activities & Carbon Dioxide 1.5.10Diagnostic Misconceptions - Plant Food 1.5.11End of Topic Test - Plants & Photosynthesis 1.5.12Diagnostic Misconceptions - Transpiration

1.6

Biological Systems & Processes

1.6.1Living Organisms 1.6.2Dichotomous Keys 1.6.3Biomechanics 1.6.4Muscles 1.6.5The Skeleton 1.6.6Bones 1.6.7Tendons and Ligaments 1.6.8Joints 1.6.9Carpals and Tarsals 1.6.10Measuring Forces 1.6.11Antagonistic Muscle Pairings 1.6.12The Respiratory System 1.6.13Gas Exchange 1.6.14Structure & Function of the Gas Exchange System 1.6.15Breathing 1.6.16Respiration 1.6.17Respiration During Exercise 1.6.18Anaerobic Respiration 1.6.19Lactic Acid 1.6.20Effects of Smoking on the Respiratory System 1.6.21Balanced Diets 1.6.22Human Growth & Development 1.6.23DNA 1.6.24Alleles 1.6.25Genotype vs Phenotype 1.6.26Punnett Squares 1.6.27The Double Circulatory System 1.6.28Heart and Blood 1.6.29Blood Vessels 1.6.30The Renal System 1.6.31Glucose & Diabetes 1.6.32Blood Glucose 1.6.33Human Illnesses 1.6.34Bacterial and Viral Infections 1.6.35Antibiotics 1.6.36Vaccinations 1.6.37How Antibiotics and Vaccines Work 1.6.38The Effects of Recreational Drug Use 1.6.39Mental Health 1.6.40Depression and Anxiety 1.6.41End of Topic Test - Muscles & Bones 1.6.42End of Topic Test - Respiration 1.6.43End of Topic Test - DNA & The Circulatory System 1.6.44End of Topic Test - Human Illnesses & Vaccination

Chemistry

2.1

Particles

2.2

Chemical Reactions

2.2.1Chemical Reactions 2.2.2Common Reactions 2.2.3Acids & Alkalis 2.2.4Reactions of Acids 2.2.5Testing for Hydrogen 2.2.6The pH Scale 2.2.7Titration 2.2.8End of Topic Test - Chemical Reactions 2.2.9Diagnostic Misconceptions - Sodium Chloride

2.3

Atoms, Elements, Compounds

2.3.1Atoms 2.3.2Elements 2.3.3Compounds & Mixtures 2.3.4Electron Configuration 2.3.5Chemical Symbols 2.3.6Chemical Formulae 2.3.7Conservation of Mass 2.3.8Vacuums 2.3.9Molecules 2.3.10End of Topic Test - Particles & Atoms 2.3.11Diagnostic Misconceptions - Law of Conservation

2.4

The Periodic Table

2.4.1Physical Properties 2.4.2Chemical Properties 2.4.3Mendeleev 2.4.4The Periodic Table 2.4.5Metals 2.4.6Non-Metals 2.4.7Properties of Metals and Non-Metals 2.4.8Alkali Metals 2.4.9Halogens 2.4.10Oxides 2.4.11End of Topic Test - The Periodic Table 2.4.12Diagnostic Misconceptions - Order of the PT

2.5

Materials & the Earth

2.6

Reactivity

2.6.1Ions 2.6.2Ionic Bonding 2.6.3State Symbols 2.6.4Balancing Chemical Equations 2.6.5Relative Formula Mass 2.6.6Calculating the Relative Formula Mass 2.6.7The Reactivity Series 2.6.8Carbon & The Reactivity Series 2.6.9Displacement Reactions 2.6.10Displacement Reactions - Halogens 2.6.11Alloys 2.6.12Metal Alloys 2.6.13End of Topic Test - Ions 2.6.14End of Topic Test - Reactivity

2.7

Energetics

2.7.1Measuring Gas Production 2.7.2Observing a Colour Change 2.7.3Analysing Reaction Rates 2.7.4Factors Affecting the Rate of Reaction 2.7.5Catalysts 2.7.6Testing for Oxygen 2.7.7Energy Changes During Reactions 2.7.8End of Topic Test - Energetics

2.8

Properties of Materials

2.8.1Testing for Gases 2.8.2Alloys 2.8.3Density 2.8.4Density of Solids, Liquids & Gases HyperLearning 2.8.5End of Topic Test - Properties of Materials

Physics

3.1

Energy

3.2

Forces & Motion

3.3

Waves

3.3.1Waves 3.3.2Types of Waves 3.3.3Observing Waves 3.3.4Wave Speed 3.3.5Earthquakes 3.3.6Hearing 3.3.7Observing Sound 3.3.8Sound waves are Longitudinal Waves 3.3.9Uses of Sound Waves 3.3.10The Interactions of Sound with Different Mediums 3.3.11Reflecting Sounds 3.3.12The Speed of Sound 3.3.13Measuring the Speed of Sound 3.3.14The Hearing Range of Humans 3.3.15The Human Ear 3.3.16Light Waves 3.3.17Coloured Light 3.3.18Observing Light 3.3.19Reflection 3.3.20Drawing a Reflected Image 3.3.21Refraction of Light 1 3.3.22Refraction of Light 2 3.3.23The Human Eye 3.3.24The Eye as a Pinhole Camera 3.3.25Lenses 3.3.26Colour 3.3.27Seeing Colour 3.3.28Colours of Light 3.3.29Drawing Waves 3.3.30Wave Interactions 3.3.31Comparing Sound & Light 3.3.32General Principles of Radiation 3.3.33Temperature & Black Bodies 3.3.34Production of Electromagnetic Waves 3.3.35Sound as Radiation 3.3.36Light as Radiation 3.3.37End of Topic Test - Sound 3.3.38End of Topic Test - Light 3.3.39End of Topic Test - Waves 3.3.40End of Topic Test - Waves 2 3.3.41Diagnostic Misconceptions - Reflection 3.3.42Diagnostic Misconceptions - Wave Speed

3.4

Electricity & Magnetism

3.5

Matter

3.6

Space Physics

3.6.1The Sun 3.6.2The Planets 3.6.3Other Astronomical Bodies 3.6.4The Milky Way 3.6.5Beyond The Milky Way 3.6.6The Seasons 3.6.7Days, Months & Years 3.6.8The Moon 3.6.9Light Years 3.6.10End of Topic Test - Space 3.6.11Diagnostic Misconceptions - Distance from the Sun

Disciplinary Knowledge

4.1

Thinking Scientifically

4.1.1Strengths & Limitations of Models 4.1.2Symbols & Formulae to Represent Scientific Ideas 4.1.3Analogies in Science 4.1.4Changing Models – Atomic Theory 4.1.5Working Safely in the Lab 4.1.6Variables 4.1.7Variables - Common Experiments 4.1.8Writing a Hypothesis & Prediction 4.1.9Planning an Experiment 4.1.10Maths Skills for Science - Mean 4.1.11Maths Skills for Science - Percentage & Equations 4.1.12Drawing Scientific Apparatus 4.1.13Observation & Measurement Skills 4.1.14Types of Data 4.1.15Graphs & Charts 4.1.16Bias in Science 4.1.17Conclude & Evaluate 4.1.18End of Topic Test - Scientific Thinking 4.1.19End of Topic Test - Experimenting

4.2

Applications of Science and its Implications

4.2.1Developing Scientific Knowledge through Technology 4.2.2Developing Technology through Science 4.2.3Ethical, Social, Economic, Political Implications 4.2.4End of Topic Test - Applications of Science

Jump to other topics

Biology

1.1

Cells, Tissues & Organs

1.2

Reproduction & Variation

1.3

Ecological Relationships & Classification

1.4

Digestion & Nutrition

1.5

Plants & Photosynthesis

1.6

Biological Systems & Processes

Chemistry

2.1

Particles

2.2

Chemical Reactions

2.3

Atoms, Elements, Compounds

2.4

The Periodic Table

2.5

Materials & the Earth

2.6

Reactivity

2.7

Energetics

2.8

Properties of Materials

2.8.1Testing for Gases 2.8.2Alloys 2.8.3Density 2.8.4Density of Solids, Liquids & Gases HyperLearning 2.8.5End of Topic Test - Properties of Materials

Physics

3.1

Energy

3.2

Forces & Motion

3.3

Waves

3.4

Electricity & Magnetism

3.5

Matter

3.6

Space Physics

Disciplinary Knowledge

4.1

Thinking Scientifically

4.2

Applications of Science and its Implications

Practice questions on Molecules

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

1
Which of the following combinations can covalent bonds form between?Multiple choice
2
What type of bonds do group 6 atoms form?Multiple choice
3
When non-metals like oxygen form bonds, what type of bond do they create, and what does this involve?Multiple choice
4
Which characteristic is commonly found in molecules held together by covalent bonds, and why is this important?Multiple choice
5
What distinguishes diatomic molecules, and how do different groups form their bonds?Multiple choice

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Vacuums

End of Topic Test - Particles & Atoms