Nigeria's free digital learning hub. Videos, lecture notes, practice questions and leaderboards aligned with CCMAS, NBTE, NCCE, WAEC, NECO, IJMB and JAMB curricula.
Loading
Nigeria's free digital learning hub. Videos, lecture notes, practice questions and leaderboards aligned with CCMAS, NBTE, NCCE, WAEC, NECO, IJMB and JAMB curricula.
Mechanical Engineering · 300 Level
This is the complete lecture note for MME304 Chemistry of materials, prepared for Mechanical Engineering students at 300 Level. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
Course code: MME 304 Course title: Chemistry of Materials Course credit load: 2 Units Series 1: Structure and Bonding in Solids • Part 1.1: Chemical Properties of Materials o Sub Part 1.1.1: Chemical Composition and Properties o Sub Part 1.1.2: Periodic Trends and Chemical Behaviour o Sub Part 1.1.3: Chemical Reactivity of Materials • Part 1.2: Types of Bonding in Solids o Sub Part 1.2.1: Ionic Bonding o Sub Part 1.2.2: Covalent Bonding o Sub Part 1.2.3: Metallic Bonding • Part 1.3: Secondary Bonding and Structure o Sub Part 1.3.1: Van der Waals Bonding o Sub Part 1.3.2: Hydrogen Bonding o Sub Part 1.3.3: Mixed Bonding in Real Materials • Part 1.4: Structure of Solids o Sub Part 1.4.1: Crystalline versus Amorphous Structure o Sub Part 1.4.2: Bonding Type and Resulting Structure o Sub Part 1.4.3: Structure-Property Relationships Arising from Bonding Introduction Every material's properties, whether it conducts electricity, resists corrosion, or deforms under load, ultimately trace back to the chemistry occurring at the atomic scale, the specific chemical properties an element possesses and the type of bonding that forms when atoms combine into a solid, and this opening Series examines exactly this chemical foundation, from basic chemical properties through the primary and secondary bonding types to the resulting solid structures these bonds produce.
The aim of this Series is to equip you with an understanding of the chemical properties relevant to materials, the primary bonding types, ionic, covalent, and metallic, the secondary bonding types, van der Waals and hydrogen bonding, and how bonding type determines a solid's resulting structure and properties. We shall commence this Series with the chemical properties of materials, before turning to the types of bonding in solids. We will then examine secondary bonding and structure, and conclude this Series by considering the structure of solids. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1: describe the chemical properties relevant to materials, • SLO 1.2: explain periodic trends in chemical behaviour, • SLO 1.3: explain ionic bonding, • SLO 1.4: explain covalent bonding, • SLO 1.5: explain metallic bonding, • SLO 1.6: describe secondary bonding, including van der Waals and hydrogen bonding, • SLO 1.7: distinguish crystalline and amorphous structure, • SLO 1.8: explain how bonding type determines structure and properties, 1.1 Chemical Properties of Materials 1.1.1 Chemical Composition and Properties Every material's chemical composition, the specific elements present and their relative proportions, directly determines the chemical properties that material subsequently exhibits, reactivity toward oxygen, water, and other environmental substances prominent examples, this composition-property relationship representing the essential starting point for chemistry's own contribution to understanding and predicting material behaviour. Chemical properties differ genuinely from the physical properties, density, melting point, and mechanical strength among them, examined more extensively in physical and mechanical metallurgy, since chemical properties specifically describe how a material's composition changes, or resists changing, through chemical reaction with its environment, this distinction worth keeping clearly in mind throughout this course's specifically chemical focus.
Worked example: Distinguishing a metal's chemical property, its tendency to oxidise in humid air, from its physical property, its density, illustrates the genuine distinction between these two property categories this course specifically focuses on the former. Application: Keeping the chemical-physical property distinction clearly in mind throughout this course correctly frames why this course specifically examines composition-driven reactivity rather than the physical properties examined elsewhere. Fill in the blank: A material's chemical composition directly determines the chemical ________ that material subsequently exhibits. 1.1.2 Periodic Trends and Chemical Behaviour An element's position within the periodic table directly predicts much of its own chemical behaviour, electronegativity, ionisation energy, and atomic radius each varying in a genuinely systematic, predictable pattern across periods and down groups, these periodic trends providing a genuinely powerful predictive tool for anticipating how a specific element will chemically behave, including how readily it forms particular bonding types, examined throughout the remainder of this Series. Applying these periodic trends allows a materials chemist to predict, before any direct experimental testing, whether two specific elements will likely form an ionic bond, a covalent bond, or metallic bonding, this predictive capability drawing directly on the electronegativity difference between the two elements involved, a genuinely useful quantitative guide examined in more depth as each specific bonding type is introduced later in this Series. Worked example: Using the electronegativity difference between two specific elements to predict whether they will likely form an ionic or covalent bond applies periodic trend reasoning directly to a genuinely practical bonding prediction. Application: Using periodic trends and electronegativity difference to predict likely bonding type before direct experimental testing is a genuinely powerful predictive tool this Series applies throughout its treatment of bonding. Fill in the blank: An element's position within the periodic table directly predicts much of its own chemical ________. 1.1.3 Chemical Reactivity of Materials A material's chemical reactivity, its tendency to undergo chemical reaction with its surrounding environment, oxygen, moisture, or other chemical species prominent examples, directly governs genuinely important practical concerns including corrosion resistance, chemical stability during processing, and long-term service life, this reactivity itself traceable directly back to the specific chemical properties and periodic trends examined earlier in this Part.
Understanding a specific material's chemical reactivity in advance, before that material is actually placed into service, allows an engineer to select an appropriate protective coating, operating environment, or alternative material choice specifically to manage genuinely significant reactivity concerns, this predictive, proactive approach considerably preferable to discovering a reactivity problem only after in-service failure has already occurred. Worked example: Predicting a specific metal's genuine susceptibility to corrosion in a humid environment, based on its known chemical reactivity, allows an engineer to select an appropriate protective coating before that metal is actually placed into service. Application: Predicting chemical reactivity proactively, before service, and selecting appropriate protective measures accordingly, is considerably preferable to discovering a reactivity problem only after in-service failure occurs. Fill in the blank: A material's chemical reactivity directly governs corrosion resistance, chemical stability, and long-term service ________. Figure 1.1: Periodic trends in electronegativity relevant to predicting bonding type. Pilot questions 1.1 1. Explain the relationship between chemical composition and chemical properties. (Linked to SLO 1.1)
2. Distinguish chemical properties from physical properties. (Linked to SLO 1.1) 3. Describe periodic trends in electronegativity, ionisation energy, and atomic radius. (Linked to SLO 1.2) 4. Explain how electronegativity difference predicts likely bonding type. (Linked to SLO 1.2) 5. Explain why predicting chemical reactivity proactively is valuable. (Linked to SLO 1.1) 1.2 Types of Bonding in Solids 1.2.1 Ionic Bonding Ionic bonding forms through the complete transfer of one or more electrons from a metal atom, which becomes a positively charged cation, to a non-metal atom, which becomes a negatively charged anion, the resulting electrostatic attraction between these oppositely charged ions holding the ionic solid together, this bonding type occurring specifically between elements with a genuinely large electronegativity difference, a metal and a non-metal most commonly. Ionic solids generally exhibit high melting points, brittleness, and electrical insulation in the solid state, since the ions themselves are held rigidly in a fixed, ordered lattice position and cannot move freely to carry electrical current, though these same ions become genuinely mobile and can conduct electricity once the ionic solid is melted or dissolved in a suitable solvent. Worked example: Explaining why solid sodium chloride does not conduct electricity, while molten or dissolved sodium chloride does, applies the ionic bonding model's distinction between fixed, immobile solid-state ions and genuinely mobile molten or dissolved ions. Application: Recognising that ionic solids conduct electricity only once melted or dissolved, not in their rigid solid state, is a genuinely useful diagnostic property for identifying ionic bonding in an unfamiliar material. Fill in the blank: Ionic bonding forms through the complete transfer of electrons from a metal atom to a ________ atom. 1.2.2 Covalent Bonding Covalent bonding forms through the genuine sharing of electron pairs between two atoms, this bonding type occurring specifically between elements with a genuinely small or negligible electronegativity difference, most commonly two non-metals, the shared electron pair, or pairs, held simultaneously by both bonded atoms' own nuclei, this shared arrangement producing a genuinely strong, highly directional bond.
Covalently bonded solids exhibit properties ranging enormously widely depending on their specific atomic arrangement, diamond, with its extended three-dimensional covalent network, exhibiting extreme hardness and a very high melting point, while other covalently bonded materials, composed instead of discrete molecules held together only by weaker secondary forces between molecules, exhibit considerably lower melting points, this wide property range directly reflecting covalent bonding's own genuinely varied structural possibilities. Worked example: Contrasting diamond's extreme hardness, arising from its extended three-dimensional covalent network, against a molecular covalent solid's considerably lower melting point illustrates covalent bonding's genuinely wide range of resulting properties. Application: Recognising that covalent bonding alone does not determine a material's properties, its specific structural arrangement, network versus molecular, mattering just as much, is essential to correctly interpreting covalent solids' considerable property diversity. Fill in the blank: Covalent bonding forms through the genuine
This is the opening of the note. Read the full note or download the PDF to continue.
