Chemical Bonding

Chemical Bonding

Middle School

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Learning Objectives

• Define the key terms: atoms, elements, molecules, and compounds.

• Explain how electron shells and the Octet Rule help atoms form chemical bonds.

• Differentiate between ionic, covalent, and metallic types of chemical bonds.

• Identify the different types of ions that are formed during ionic bonding.

Key Vocabulary

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Atom

An atom is the basic building block of a chemical element and the smallest unit of matter.

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Molecule

A molecule is a group of two or more atoms held together by strong chemical bonds.

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Ionic Bond

This chemical bond is formed when electrons are completely transferred from a metal to a nonmetal.

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Covalent Bond

A chemical bond formed when two nonmetallic elements share pairs of electrons to become more stable.

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Octet Rule

The tendency of atoms to prefer having eight electrons in their outermost shell for achieving stability.

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Building Blocks of Matter

Molecules

• An element is a pure substance that is made of only one type of atom.

• When atoms join together by chemical bonds, they form molecules.

• For example, an oxygen molecule (O₂) has two oxygen atoms bonded together.

Compounds

• A compound is a molecule formed from two or more different elements chemically bonded.

• All compounds are molecules, but not all molecules are compounds.

• Water (H₂O) is a compound made of hydrogen and oxygen atoms.

Multiple Choice

Which statement accurately describes the relationship between molecules and compounds?

• Molecules and compounds are completely unrelated.

• All compounds are molecules.

• Only elements can form molecules, not compounds.

• All molecules are compounds.

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Electrons and the Octet Rule

• An atom's electrons determine its behavior; the atomic number tells you how many.

• These electrons are arranged in shells, with the first shell holding up to 2.

• The second and third electron shells can each hold up to 8 electrons.

• Atoms bond to get a full outer shell, which is called the Octet Rule.

Multiple Choice

According to the Octet Rule, why do atoms form chemical bonds?

• To get rid of all their electrons.

• To change their atomic number.

• To increase the number of electron shells they have.

• To gain, lose, or share electrons to achieve a full outer shell.

Types of Chemical Bonds

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Ionic Bonds

• ​Electrons are transferred from a metal to a nonmetal.

• ​​This creates charged particles called positive and negative ions.

• ​An example is Sodium Chloride (NaCl), or table salt.

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Covalent Bonds

• ​Electron pairs are shared between two nonmetallic elements.

• ​​Atoms cooperate to complete their outer shells without transferring electrons.

• ​Examples are water (H₂O) and carbon dioxide (CO₂).

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Metallic Bonds

• ​This type of chemical bond is found between metal atoms.

• ​​Positive metal ions are attracted to a surrounding "sea" of electrons.

• ​This bonding allows different metals to form solutions called alloys.

Multiple Choice

A chemical bond is formed between a metal and a nonmetal through the transfer of electrons. What type of bond is this?

• Hydrogen Bond

• Metallic Bond

• Ionic Bond

• Covalent Bond

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Common Misconceptions About Chemical Bonds

Misconception	Correction
All bonds involve giving away or taking electrons.	Only ionic bonds transfer electrons. Others share them in different ways.
Molecules and compounds are the exact same thing.	A compound has different elements. A molecule can have identical atoms (O2).
Atoms want to have 8 electrons in total.	Atoms want 8 electrons in their outermost shell, not in total.

Multiple Choice

If an element has 7 electrons in its outer shell, what is it most likely to do to follow the Octet Rule and what kind of ion will it form?

• Lose 7 electrons and form a positive ion.

• Share 1 electron and form a positive ion.

• Gain 1 electron and form a positive ion.

• Gain 1 electron and form a negative ion.

Multiple Choice

How do covalent bonds help atoms like Oxygen (O) and Hydrogen (H) achieve stability in a water molecule (H₂O)?

• By forming positive and negative ions that attract each other.

• By creating a sea of electrons around the atoms.

• By transferring an electron from Hydrogen to Oxygen.

• By sharing electrons to complete their outer shells.

Multiple Choice

A substance is formed from two different nonmetals that are sharing electrons. Based on this information, what can you conclude about the substance?

• It is an element with ionic bonds.

• It is a compound with covalent bonds.

• It is a metal with covalent bonds.

• It is an alloy with metallic bonds.

Multiple Choice

What is the main difference between how electrons act in ionic bonds and metallic bonds?

• In ionic bonds, electrons are shared; in metallic bonds, they are transferred.

• Both bond types involve atoms sharing electrons only with an adjacent atom.

• Both bond types involve the complete transfer of electrons to nonmetals.

• In ionic bonds, electrons are transferred; in metallic bonds, they form a shared 'sea'.

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Summary

• Atoms join together using chemical bonds to form molecules.

• Atoms bond to achieve a full and stable outer electron shell.

• In ionic bonds, electrons are transferred from a metal to a nonmetal.

• In covalent bonds, electrons are shared between nonmetal atoms.

• Metallic bonds have a "sea" of shared electrons between metal atoms.

• Elements have one type of atom, while compounds have different types.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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• 3

• 4