CHM 212 — Inorganic Chemistry I: Lecture Note

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LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: CHM 212 Course title: Inorganic Chemistry I Course Unit: 2 Units C: LH 30 Series 1: Chemistry of First-Row Transition Metals Series 2: Coordination Chemistry and Crystal Field Theory Series 3: Comparative Chemistry of Selected Main Group Elements Series 4: Fundamentals of Organometallic Chemistry Series 5: Roles of Metals in Biochemical Systems and Redox Concepts Suggested Outline Part 1.1: Introduction to First-Row Transition Metals Sub-Part 1.1.1: Position in the periodic table and general characteristics Sub-Part 1.1.2: Common oxidation states and variable valency Sub-Part 1.1.3: General physical and chemical properties Part 1.2: Electronic Configurations and Magnetic Properties Sub-Part 1.2.1: d-orbital occupancy and electronic structures Sub-Part 1.2.2: Magnetic behaviour and paramagnetism Sub-Part 1.2.3: Trends across the first-row transition series Part 1.3: Coordination and Complex Formation Sub-Part 1.3.1: Nature of transition metal complexes Sub-Part 1.3.2: Examples of common coordination compounds Sub-Part 1.3.3: Importance in industrial and biological systems Part 1.4: Applications and Significance of Transition Metals Sub-Part 1.4.1: Catalytic roles in industry Sub-Part 1.4.2: Use in materials and alloys Sub-Part 1.4.3: Biological importance of selected transition metals

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Introduction Transition metals are often described as the workhorses of inorganic chemistry because of their wide-ranging properties and applications. The first-row transition metals, stretching from scandium to zinc, are particularly important as they display variable oxidation states, form colourful compounds, and play key roles in catalysis and biological systems. By studying them, you will gain insight into the fundamental principles that underpin much of modern chemistry, from industrial processes to materials science. The aim of this Series is to introduce you to the chemistry of the first-row transition metals, focusing on their structures, properties, and applications. It is designed to help you appreciate how these elements behave and why they are so significant in both theoretical and practical contexts. We shall commence this Series by examining the position of the first-row transition metals in the periodic table, their general characteristics, and their common oxidation states. Next, we will explore their electronic configurations and magnetic properties, paying attention to trends across the series. Following that, we will consider their ability to form coordination compounds and complexes, with examples drawn from industry and biology. Finally, we will wrap up by discussing their applications, including their catalytic roles, use in alloys, and biological importance, thereby rounding off a comprehensive overview of this fascinating group of elements. Series Learning Outcomes Upon completing this Series, you should be able to: SLO 1.1 define the position and general characteristics of the first-row transition metals in the periodic table, SLO 1.2 explain the common oxidation states and variable valency of first-row transition metals, SLO 1.3 analyse the electronic configurations and magnetic properties of first-row transition metals, SLO 1.4 describe the trends in physical and chemical properties across the first-row transition series, SLO 1.5 illustrate the nature of coordination and complex formation in first-row transition metals with relevant examples, and SLO 1.6 evaluate the industrial, material, and biological applications of first-row transition metals. 1.1 Introduction to First-Row Transition Metals 1.1.1 Position in the periodic table and general characteristics The first-row transition metals are the elements from scandium (Sc) to zinc (Zn) in the periodic table. They are located in period 4 and occupy the d-block, meaning their distinguishing feature is the gradual filling of the 3d orbitals. These elements are known for their ability to form coloured compounds, exhibit variable oxidation states, and act as catalysts in chemical reactions. Their position in the periodic table makes them a bridge between the s-block and p-block elements, displaying properties of both metals and non-metals. Fill in the blank: The first-row transition metals occupy the __________ block of the periodic table.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.1: Position of first-row transition metals in the periodic table 1.1.2 Common oxidation states and variable valency A defining feature of transition metals is their ability to exhibit variable oxidation states, which means they can lose different numbers of electrons depending on the chemical environment. For example, iron can exist as Fe²⁺ or Fe³⁺, while manganese can show oxidation states ranging from +2 to +7. This variability arises from the close energy levels of the 3d and 4s orbitals, allowing electrons to be removed from both. Fill in the blank: The variability in oxidation states of transition metals arises because the __________ and __________ orbitals have similar energy levels.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Table 1.1: Common oxidation states of selected first-row transition metals 1.1.3 General physical and chemical properties The first-row transition metals share several physical properties, such as high melting points, high densities, and metallic lustre. Their chemical properties include the ability to form complexes, catalytic activity, and the tendency to produce compounds with vivid colours. For instance, copper(II) sulphate is bright blue, while chromium(III) chloride is green. These properties make them essential in both industrial and biological contexts. Their catalytic behaviour is exploited in processes such as the Haber process (iron catalyst) and the Contact process (vanadium catalyst). Biologically, transition metals are found in enzymes and proteins that sustain life. Fill in the blank: The colourful nature of transition metal compounds is often due to __________ electronic transitions.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Plate 1.1: Colourful compounds of first-row transition metals Pilot questions 1.1 The first-row transition metals occupy the __________ block of the periodic table. A. s-block B. p-block C. d-block D. f-block Which oxidation states are most common for iron? A. +1 and +2 B. +2 and +3 C. +3 and +4 D. +4 and +5 The variability in oxidation states of transition metals arises because the __________ and __________ orbitals have similar energy levels. A. 2p and 3p B. 3d and 4s C. 4p and 5s D. 3s and 3p The colourful nature of transition metal compounds is often due to __________ electronic transitions. A. s–p B. p–d C. d–d D. f–d Which property is typical of first-row transition metals compared to s-block elements? A. Low melting points

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS B. Softness C. High density and hardness D. Lack of catalytic activity 1.2 Electronic Configurations and Magnetic Properties 1.2.1 d-orbital occupancy and electronic structures The electronic configuration of an element describes the arrangement of its electrons in orbitals. For the first-row transition metals, the distinguishing electrons enter the 3d orbitals after the 4s orbital has been filled. For example, scandium (Sc) has the configuration [Ar] 3d¹ 4s², while zinc (Zn) has [Ar] 3d¹⁰ 4s². Because the 3d and 4s orbitals are close in energy, electrons can be lost from either, leading to the variable oxidation states typical of transition metals. This flexibility in electron occupancy is the foundation of their rich chemistry. Fill in the blank: The first-row transition metals are characterised by the gradual filling of the __________ orbitals. Figure 1.2: Progressive filling of 3d orbitals in first-row transition metals 1.2.2 Magnetic behaviour and paramagnetism

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS The magnetic properties of transition metals depend on the presence of unpaired electrons in their d-orbitals. A substance with unpaired electrons exhibits paramagnetism, meaning it is weakly attracted to a magnetic field. Conversely, if all d-orbitals are paired, the substance is diamagnetic, showing weak repulsion from a magnetic field. For example, manganese(II) with a 3d⁵ configuration has five unpaired electrons and is strongly paramagnetic, while zinc(II) with a 3d¹⁰ configuration has no unpaired electrons and is diamagnetic. Fill in the blank: Transition metals with completely filled d-orbitals, such as zinc, are described as __________. Table 1.2: Magnetic behaviour of selected first-row transition metals Element Electronic configuration Magnetic behaviour Sc [Ar] 3d¹ 4s² Paramagnetic Mn [Ar] 3d⁵ 4s² Strongly paramagnetic Fe [Ar] 3d⁶ 4s² Paramagnetic Cu [Ar] 3d¹⁰ 4s¹ Weakly paramagnetic Zn [Ar] 3d¹⁰ 4s² Diamagnetic 1.2.3 Trends across the first-row transition series Across the series from Sc to Zn, several trends can be observed:

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