Grade 9 Chemistry Unit 5 : Chemical Bonding

Unit 5, “Chemical Bonding,” explores the fundamental forces that hold atoms together to form the molecules and compounds that make up our world. In this crucial unit of the Grade 9 Ethiopian Chemistry curriculum, you’ll learn why and how atoms connect, creating the incredible diversity of substances we see every day.

Chapter 5.1 – Chemical Bonding

This chapter introduces the core concepts of why and how atoms interact.

• Define a chemical bond as the force of attraction that holds atoms together.
• Understand the driving force behind bonding: the octet rule, which states that atoms tend to gain, lose, or share electrons to achieve a stable electron configuration like that of a noble gas.
• Recognize the role of valence electrons (the outermost electrons) as the key players in forming chemical bonds.

Chapter 5.2 – Ionic Bonding

Learn about the bonds formed when electrons are transferred from one atom to another.

• Define ionic bonding as the electrostatic attraction between positively charged ions (cations) and negatively charged ions (anions).
• Understand how ionic bonds typically form between metals (which lose electrons) and nonmetals (which gain electrons).
• Use Lewis dot structures to illustrate the transfer of electrons in the formation of ionic compounds like sodium chloride (NaCl). * Describe the characteristic properties of ionic compounds: they are typically crystalline solids with high melting points and conduct electricity when molten or dissolved in water.

Chapter 5.3 – Covalent Bonding

Discover the bonds that are formed when atoms share electrons.

• Define covalent bonding as the sharing of electron pairs between two nonmetal atoms to form molecules.
• Learn to draw Lewis dot structures for molecules, identifying single, double, and triple bonds.
• Distinguish between:
  • Nonpolar covalent bonds.
  • Polar covalent bonds.
• Explore the properties of covalent compounds.

Chapter 5.4 – Metallic Bonding

Explore the unique type of bonding that gives metals their special properties.

• Describe metallic bonding using the “sea of electrons” model.
• Understand how this model explains the signature properties of metals.

Learning Outcomes

By the end of Unit 5, you will be able to:

• Define a chemical bond and explain the octet rule.
• Describe the formation of ionic, covalent, and metallic bonds.
• Draw Lewis dot structures for simple ionic and covalent compounds.
• Differentiate between polar and nonpolar covalent bonds.
• Relate the physical properties of a substance to its type of chemical bonding.
• Explain the properties of metals using the electron sea model.