Class 11 Chemistry - ANDHRA-PRADESH
Classification of Elements and Periodicity in Properties
The chapter 'Classification of Elements and Periodicity in Properties' in Class 11 Chemistry is foundational for understanding chemical behavior. It traces the historical development of the periodic table, culminating in the Modern Periodic Law based on atomic number. Students learn about the electronic configurations of elements in periods and groups, and the periodic trends in physical and chemical properties such as atomic radius, ionization enthalpy, electron gain enthalpy, and electronegativity. This chapter is extremely important for the Andhra Pradesh (BSEAP) board examinations as it forms the basis for chemical bonding, coordination chemistry, and inorganic chemistry as a whole.
Start Learning FreeKey Concepts
Modern Periodic Law
Properties of elements are a periodic function of their atomic numbers, which resolved anomalies in Mendeleev's periodic table based on atomic mass.
Atomic and Ionic Radii
Atomic radius generally decreases across a period due to increasing effective nuclear charge and increases down a group due to the addition of principal energy shells.
Ionization Enthalpy
The energy required to remove an electron from an isolated gaseous atom in its ground state, which increases across a period and decreases down a group.
Electron Gain Enthalpy
The enthalpy change when an electron is added to a neutral gaseous atom to form an anion, becoming more negative across a period and less negative down a group.
Electronegativity
The qualitative measure of an atom's ability to attract shared electrons in a covalent bond, increasing across a period and decreasing down a group.
Important Formulas
Board Exam Info
In the Andhra Pradesh (BSEAP) Class 11 Chemistry board examinations, this chapter typically carries around 4 to 6 marks. Questions usually include very short answer questions (2 marks) on periodic trends and definitions, and short answer questions (4 marks) explaining anomalies in ionization enthalpy or electron gain enthalpy.
Frequently Asked Questions
Noble gases are measured in terms of van der Waals radius rather than covalent radius, which inherently accounts for non-bonding interactions and is naturally larger.
Noble gases are measured using van der Waals radius which is larger than covalent radius.
Why does fluorine have a lower electron gain enthalpy than chlorine?
Due to the small size of the fluorine atom, the incoming electron experiences strong interelectronic repulsions in its compact 2p orbitals, making chlorine's electron addition more exothermic.
What is screening effect or shielding effect?
The repulsion felt by valence electrons from the inner-shell electrons, which reduces the nuclear charge experienced by the outer electrons.
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