EONS LEARNING

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      • Study Skills
      • Periodic Table
      • Common Ion Sheet
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    • Unit 1: Beginning Chemistry >
      • Lesson 1: The Atom >
        • What is an Atom?
        • The Structure of Atoms
        • The Periodic Table
        • Modeling Atoms
      • Lesson 2: Chemical Bonding >
        • Why Do Atoms Form Bonds?
        • Ionic Bonding
        • Covalent Bonding
        • Intermolecular Attraction
      • Lesson 3: Chemical Nomenclature >
        • Octet Rule
        • Ionic Compounds
        • Covalent Molecules
      • Lesson 4: Molecular Molecules >
        • Modeling Ionic Compounds
        • Modeling Covalent Molecules
      • Lesson 5: States of Matter >
        • States of Matter
        • Phase Changes
      • Lesson 6: Density >
        • What is Density?
        • Calculating Density
      • Lesson 7: Thermodynamics >
        • Temperature
        • Heat
        • Gas Laws
      • Lesson 8: Solution Chemistry >
        • Diffusion
        • Solutions and Molarity
        • Semi-Permeable Membranes
      • Lesson 9: Thermal Expansion >
        • Thermal Expansion
    • Unit 2: Earth Science >
      • Lesson 10: Earth at a Glance >
        • Perspective
        • Maps
      • Lesson 11: Layers of the Earth >
        • Layers of the Earth
      • Lesson 12: Plate Tectonics >
        • Plate Tectonics
      • Lesson 13: Rocks and Minerals >
        • Rocks and Minerals
      • Lesson 14: Particle Sorting >
        • Differentiation
        • Deposition of Sediment
      • Lesson 15: The Atmosphere >
        • Composition of the Atmosphere
        • Layers of the Atmosphere
        • Change Over Time
        • Atmospheric Disruption
    • Unit 3: The Cell >
      • Lesson 16: Life >
        • What is Life?
        • Structural Hierarchy of Living Things
      • Lesson 17: Biochemistry >
        • Intro to Biochemistry
        • Water
        • Micromolecules
        • Energy, Carbohydrates, Lipids
        • Protein and Nucleic Acid
      • Lesson 18: Cells >
        • What are Cells?
        • Microscopy
        • Plant and Animal Cells
      • Lesson 19: Membrane Transport >
        • A Special Environment
        • The Structure of Membranes
        • Membrane Transport
      • Lesson 20: Energy and Cell Respiration >
        • Energy in Biology
        • Energy Diagrams
        • Glycolysis and Anaerobic Respiration
        • Aerobic Cellular Respiration
      • Lesson 21: Photosynthesis >
        • Plants Get Energy From The Sun
        • Photosynthesis Process
        • Energy, Ecosystems, and the Environment
    • Unit 4: Anatomy and Physiology >
      • Lesson 22: The Human Body >
        • What Are Bodies Made Of?
        • What Do Bodies Do?
      • Lesson 23: The Nervous System >
        • The Nervous System
        • Neuronal Communication
        • The Central Nervous System
      • Lesson 24: The Endocrine System >
        • The Endocrine System
        • Hormones
        • Hormones, Puberty, and Reproduction
      • Lesson 25: The Integumentary System >
        • The Integumentary System
      • Lesson 26: The Musculoskeletal System >
        • The Skeletal System
        • The Muscular System
        • Anatomy Of The Musculoskeletal System
      • Lesson 27: The Cardiovascular System >
        • Blood and Blood Vessels
        • The Heart
      • Lesson 28: The Respiratory System >
        • The Respiratory System
      • Lesson 29: The Digestive System >
        • The Digestive System
        • Nutrition
      • Lesson 30: The Excretory System >
        • The Excretory System
      • Lesson 31: The Immune System >
        • Disease and Infection
        • Immunity
    • Units 5-6 Coming Soon
  • Workbench
    • Unit 1 >
      • EIS >
        • Lesson 1: Atoms
        • Lesson 2: Chemical Bonding
        • Lesson 3: Chemical Nomenclature
        • Lesson 4: Molecular Models
        • Lesson 5: States of Matter
        • Lesson 6: Density
        • Lesson 7: Thermodynamics
        • Lesson 8: Solution Chemistry
        • Lesson 9: Thermal Expansion
      • Unit 1: Project
      • Unit 1: Exam Review
      • Unit 1: Exam
    • Unit 2 >
      • EIS >
        • Lesson 10: Earth at a Glance
        • Lesson 11: Layers of the Earth
        • Lesson 12: Plate Tectonics
        • Lesson 13: Rocks and Minerals
        • Lesson 14: Particle Sorting
        • Lesson 15: The Atmosphere
      • Unit 2: Project
      • Unit 2: Exam Review
      • Unit 2: Exam
    • Unit 3 >
      • EIS >
        • Lesson 16: Life
        • Lesson 17: Biochemsitry
        • Lesson 18: Cells
        • Lesson 19: Membrane Transport
        • Lesson 20: Energy and Cell Respiration
        • Lesson 21: Photosynthesis
      • Unit 3: Project
      • Unit 3: Exam Review
      • Unit 3: Exam
    • Unit 4 >
      • EIS >
        • 22: The Human Body
        • 23: The Nervous System
        • 24: The Endocrine System
        • 25: The Integumentary System
        • 26: The Musculoskeletal System
        • 27: The Cardiovascular System
        • 28: The Respiratory System
        • 29: The Digestive System
        • 30: The Excretory System
        • 31: The Immune System
      • Unit 4 Project
      • Unit 4 Exam Review
      • Unit 4 Exam
    • Units 5-6 Coming Soon
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  • Home
  • About Us
  • Classroom
    • Resources >
      • Study Skills
      • Periodic Table
      • Common Ion Sheet
      • The Scientific Method
      • Doing Background Research
    • Introduction and Course Philosophy
    • Unit 1: Beginning Chemistry >
      • Lesson 1: The Atom >
        • What is an Atom?
        • The Structure of Atoms
        • The Periodic Table
        • Modeling Atoms
      • Lesson 2: Chemical Bonding >
        • Why Do Atoms Form Bonds?
        • Ionic Bonding
        • Covalent Bonding
        • Intermolecular Attraction
      • Lesson 3: Chemical Nomenclature >
        • Octet Rule
        • Ionic Compounds
        • Covalent Molecules
      • Lesson 4: Molecular Molecules >
        • Modeling Ionic Compounds
        • Modeling Covalent Molecules
      • Lesson 5: States of Matter >
        • States of Matter
        • Phase Changes
      • Lesson 6: Density >
        • What is Density?
        • Calculating Density
      • Lesson 7: Thermodynamics >
        • Temperature
        • Heat
        • Gas Laws
      • Lesson 8: Solution Chemistry >
        • Diffusion
        • Solutions and Molarity
        • Semi-Permeable Membranes
      • Lesson 9: Thermal Expansion >
        • Thermal Expansion
    • Unit 2: Earth Science >
      • Lesson 10: Earth at a Glance >
        • Perspective
        • Maps
      • Lesson 11: Layers of the Earth >
        • Layers of the Earth
      • Lesson 12: Plate Tectonics >
        • Plate Tectonics
      • Lesson 13: Rocks and Minerals >
        • Rocks and Minerals
      • Lesson 14: Particle Sorting >
        • Differentiation
        • Deposition of Sediment
      • Lesson 15: The Atmosphere >
        • Composition of the Atmosphere
        • Layers of the Atmosphere
        • Change Over Time
        • Atmospheric Disruption
    • Unit 3: The Cell >
      • Lesson 16: Life >
        • What is Life?
        • Structural Hierarchy of Living Things
      • Lesson 17: Biochemistry >
        • Intro to Biochemistry
        • Water
        • Micromolecules
        • Energy, Carbohydrates, Lipids
        • Protein and Nucleic Acid
      • Lesson 18: Cells >
        • What are Cells?
        • Microscopy
        • Plant and Animal Cells
      • Lesson 19: Membrane Transport >
        • A Special Environment
        • The Structure of Membranes
        • Membrane Transport
      • Lesson 20: Energy and Cell Respiration >
        • Energy in Biology
        • Energy Diagrams
        • Glycolysis and Anaerobic Respiration
        • Aerobic Cellular Respiration
      • Lesson 21: Photosynthesis >
        • Plants Get Energy From The Sun
        • Photosynthesis Process
        • Energy, Ecosystems, and the Environment
    • Unit 4: Anatomy and Physiology >
      • Lesson 22: The Human Body >
        • What Are Bodies Made Of?
        • What Do Bodies Do?
      • Lesson 23: The Nervous System >
        • The Nervous System
        • Neuronal Communication
        • The Central Nervous System
      • Lesson 24: The Endocrine System >
        • The Endocrine System
        • Hormones
        • Hormones, Puberty, and Reproduction
      • Lesson 25: The Integumentary System >
        • The Integumentary System
      • Lesson 26: The Musculoskeletal System >
        • The Skeletal System
        • The Muscular System
        • Anatomy Of The Musculoskeletal System
      • Lesson 27: The Cardiovascular System >
        • Blood and Blood Vessels
        • The Heart
      • Lesson 28: The Respiratory System >
        • The Respiratory System
      • Lesson 29: The Digestive System >
        • The Digestive System
        • Nutrition
      • Lesson 30: The Excretory System >
        • The Excretory System
      • Lesson 31: The Immune System >
        • Disease and Infection
        • Immunity
    • Units 5-6 Coming Soon
  • Workbench
    • Unit 1 >
      • EIS >
        • Lesson 1: Atoms
        • Lesson 2: Chemical Bonding
        • Lesson 3: Chemical Nomenclature
        • Lesson 4: Molecular Models
        • Lesson 5: States of Matter
        • Lesson 6: Density
        • Lesson 7: Thermodynamics
        • Lesson 8: Solution Chemistry
        • Lesson 9: Thermal Expansion
      • Unit 1: Project
      • Unit 1: Exam Review
      • Unit 1: Exam
    • Unit 2 >
      • EIS >
        • Lesson 10: Earth at a Glance
        • Lesson 11: Layers of the Earth
        • Lesson 12: Plate Tectonics
        • Lesson 13: Rocks and Minerals
        • Lesson 14: Particle Sorting
        • Lesson 15: The Atmosphere
      • Unit 2: Project
      • Unit 2: Exam Review
      • Unit 2: Exam
    • Unit 3 >
      • EIS >
        • Lesson 16: Life
        • Lesson 17: Biochemsitry
        • Lesson 18: Cells
        • Lesson 19: Membrane Transport
        • Lesson 20: Energy and Cell Respiration
        • Lesson 21: Photosynthesis
      • Unit 3: Project
      • Unit 3: Exam Review
      • Unit 3: Exam
    • Unit 4 >
      • EIS >
        • 22: The Human Body
        • 23: The Nervous System
        • 24: The Endocrine System
        • 25: The Integumentary System
        • 26: The Musculoskeletal System
        • 27: The Cardiovascular System
        • 28: The Respiratory System
        • 29: The Digestive System
        • 30: The Excretory System
        • 31: The Immune System
      • Unit 4 Project
      • Unit 4 Exam Review
      • Unit 4 Exam
    • Units 5-6 Coming Soon
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Covalent Molecules

Covalent molecules, like ionic compounds, arise when multiple atoms join together in a bond. As you’ve learned, covalent bonds are quite different from ionic bonds in that atoms share electrons--rather than giving them up or taking them entirely--in order to achieve a stable configuration (like an octet). You should make sure you understand this principle before moving on with the nomenclature.

Without further adieu, I now present the main attraction: the mystical, the magical, the amazing and powerful, the one and only (drum roll please).... "Chemical Nomenclature of Covalent Molecules!" (Hold for roars and applause).

Long-form Naming

Long-form naming of covalent molecules isn't all that different than it is for naming ionic compounds. Like with ionic compounds, you first name the first element, and then the second, replacing the ending of the second with "-ide". However, with ionic compounds, two atoms can really only join in one way, because the charges have to balance. You would never find NaCl2 in nature. However, the atoms in covalent molecules are not charged. They can find different ways of sharing to make them most stable. For example, I could have N2O (also known as laughing gas), or I could have NO2 (an air pollutant, which is actually not particularly stable because nitrogen doesn’t have a full octet and is instead something called a free radical):

Picture
You’ll have some practice putting these little molecular puzzles together later. For now, let’s focus on naming. Obviously, I can't just call these both "nitrogen oxide," because you wouldn't know which I was talking about—imagine a dentist accidentally giving a patient a mouthful of pure pollution instead of laughing gas! To avoid this problem, chemists have come up with the very clever solution of using latin prefixes to name covalent molecules. These prefixes include:
Picture

Just pop these suckers onto the beginning of your basic compound name (i.e., nitrogen oxide to nitrogen dioxide, for NO2, or dinitrogen monoxide, for N2O), and you have yourself a covalent compound. Beautiful, isn't it?

Note that "mono-" is only used on the second-listed atom (the same one that gets its ending changed to "-ide"). It is assumed that there is only one of the first-listed atom (the central atom), unless specified otherwise.

As with so many things that you've learned so far in this course, the process of naming covalent molecules is easier to learn by example than simply by reading about it. So, look through this chart and see if you can guess the names of the compounds, and check yourself by clicking to reveal the answer:

Knowledge is power! This table will tell you more about all the compounds you just saw. ​

BF₃
Smelly, colorless, toxic gas used as a building block for other boron compounds
SF₆
- Makes your voice deep
- Green house gas
​H₂O
- Necessary for survival for almost all living things
- Tasty beverage
​PCl₅
 Adds chlorine to other things (useful in the lab)
​N₂H₄
- Colorless, flammable liquid
- Antidepressant 

Molecular Formula

Pretty simple: just do the same thing, backwards. The advantage of using the Greek prefixes is that you don't have to figure out how many of each atom there should be: it just tells you. So, sulfur hexafluoride becomes SF6, and dihydrogen monoxide becomes H2O. It's that easy.

Common Names

In general, we chemists like to use the proper chemical name for things most of the time. That being said, you'd be hard pressed to find a chemist who refers to H2O as dihydrogen monoxide in their standard day-to-day conversations. They'll just say water. The same principle applies to a few other compounds as well, which are listed below. You should know these for your general knowledge.

Molecular Formula
Common Name
Chemical Name
What it does
​H₂O
water
dihydrogen monoxide
survival of living things
NH​₃
ammonia
nitrogen trihydride
smelly bathroom cleaner
CH₄
methane
carbon tetrahydride
natural gas (and farts, ew!)
O​₃
ozone
trioxygen
atmosphere, protects earth from harmful UV rays

Organic Molecules

Organic molecules are molecules made up mostly of carbon, hydrogen, and oxygen. Living things are made up mostly of organic molecules. They can be very big, very complex, and involve diverse arrangements of even the same number of component atoms. For this reason, they get their own, more complicated naming scheme, which you do not need to know for this class. Some simple examples include things with —OH groups on carbon backbones being called “alcohols” and ending in the suffix “–ol,” or sugars ending in “–ose.”

Diatomic Molecules

Interestingly enough, there are some molecules that are only found in nature as molecules, never as individual elements. The diatomic gases are among them. These molecules—H2, N2, O2, F2, Cl2, Br2, and I2—are only found in nature in pairs (i.e., bound to themselves). Because these molecules are quite common and are important in a number of chemical reactions, you should know them.


​There are a few useful tricks for memorizing which elements are diatomic. One of my favorites is the mnemonic "HOFBrINCl" (pronounced "hof-brink-el"), which, as you'll notice, includes the atomic symbols of all of the diatomic elements. Another way to remember makes use of the periodic table, highlighting the "royal seven" elements (there are 7 diatomic elements in total, which look like a 7 on the periodic table. Hydrogen makes a crown.)
Picture
In terms of naming these diatomic molecules, we chemists generally don't say "dihydrogen" or "dioxygen." Instead, we'll just say "hydrogen" or "hydrogen gas," and switch to "elemental hydrogen" when we're talking about the atom itself.

Summary

This video gives a great overview of naming covalent compounds:
You should know:
  • How to write the long-form name of a covalent molecule, given the molecular formula. This requires you to know the standard greek prefixes for numbers.
  • How to write the molecular formula of a covalent molecule, given the long-form name.
  • The chemical formulas for the common elements water, ammonia, methane, and ozone.
  • Which elements are only found in nature as diatomic elements.

Learning Activity

Picture
Lesson 4: modeling ionic compounds
Lesson 3: "exploration in science"

Content contributors: Emma Moulton and Eli Levine
© COPYRIGHT 2020. ALL RIGHTS RESERVED.