Chapter 3: Classification of Elements and Periodicity in Properties
Chemistry Part-1 • Class 11
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Chapter Analysis
Intermediate28 pages • EnglishQuick Summary
The chapter 'Classification of Elements and Periodicity in Properties' explores the development of the periodic table, emphasizing the modern periodic law which arranges the elements by atomic number. This systematic arrangement explains periodic trends in elemental properties, such as atomic radii, ionization enthalpy, and electronegativity. It delineates the classification of elements into s, p, d, and f blocks, and discusses the trends in chemical reactivity and physical properties across periods and groups.
Key Topics
- •Development of the periodic table
- •Modern periodic law
- •Classification into s, p, d, f blocks
- •Periodic trends in physical properties
- •Periodic trends in chemical reactivity
- •Mendeleev’s and Modern Periodic Table
- •Anomalous properties of second-period elements
- •Diagonal relationships
Learning Objectives
- ✓Understand the historical development of the periodic table.
- ✓Comprehend the significance of atomic number and electronic configuration.
- ✓Recognize periodic trends in chemical and physical properties.
- ✓Classify elements into s, p, d, and f blocks.
- ✓Compare reactivity and correlate it with elemental occurrence.
- ✓Use scientific terminology related to elemental properties.
Questions in Chapter
What is the basic theme of organisation in the periodic table?
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Which important property did Mendeleev use to classify the elements in his periodic table and did he stick to that?
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What is the basic difference in approach between the Mendeleev’s Periodic Law and the Modern Periodic Law?
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On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.
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In terms of period and group where would you locate the element with Z = 114?
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Additional Practice Questions
What are the benefits of classifying elements in the periodic table?
mediumAnswer: Classifying elements in the periodic table helps in predicting their properties and reactions, understanding trends among various groups and periods, and simplifying the study of the large number of elements.
Explain the significance of the periodic law to modern chemistry.
hardAnswer: The periodic law provides a framework to predict elemental properties based on their position in the periodic table, thus aiding in the study and categorization of chemical elements and their interactions.
How do ionization energies vary across a period and down a group?
mediumAnswer: Ionization energies generally increase across a period due to increasing nuclear charge and decrease down a group due to increasing atomic size.
Why are the elements in the same group said to have similar properties?
easyAnswer: Elements in the same group have similar valence shell electronic configurations, leading to similarities in chemical behavior and properties.
Discuss the relationship between electron gain enthalpy and non-metallic character.
mediumAnswer: A higher negative electron gain enthalpy indicates a stronger tendency to gain electrons, which correlates with increased non-metallic character.
Describe the general trend of electronegativity in the periodic table.
easyAnswer: Electronegativity generally increases across a period from left to right and decreases down a group.
How is the modern periodic table arranged?
easyAnswer: The modern periodic table is arranged by increasing atomic number, with elements placed in rows (periods) based on the filling order of electron shells, and columns (groups) sharing chemical properties.
Provide an example of a diagonal relationship in the periodic table.
hardAnswer: A diagonal relationship exists between lithium and magnesium, where both share a tendency to form covalent compounds rather than ionic, unlike their respective groups.
Explain the term 'periodic trend' in elemental properties.
mediumAnswer: Periodic trends refer to patterns observed in elemental properties (such as atomic radius, electronegativity) as one moves across the periods or down the groups of the periodic table.
Why do transition elements exhibit variable valencies?
hardAnswer: Transition elements exhibit variable valencies due to the involvement of (n-1)d electrons along with ns electrons in bonding.