Class 10 Science - KARNATAKA
Periodic Classification of Elements
The chapter Periodic Classification of Elements in Karnataka SSLC Science explores how scientists organized the known elements to study their properties systematically. Students learn about early attempts like Dobereiner's Triads and Newlands' Law of Octaves, Mendeleev's Periodic Table, and finally the Modern Periodic Table proposed by Henry Moseley. This chapter is extremely important for board exams as it tests foundational concepts of atomic structure, electronic configurations, and periodic trends such as valency, atomic size, and metallic character, which frequently appear in both objective and descriptive questions.
Start Learning FreeKey Concepts
Mendeleev's Periodic Law
States that the properties of elements are the periodic function of their atomic masses.
Modern Periodic Law
States that properties of elements are a periodic function of their atomic numbers.
Groups and Periods
The vertical columns in the Modern Periodic Table are called groups (18 in total) and horizontal rows are called periods (7 in total).
Valency
The combining capacity of an element, determined by the number of valence electrons present in the outermost shell.
Atomic Size
Refers to the radius of an atom, which generally decreases across a period from left to right and increases down a group.
Important Formulas
Board Exam Info
In the Karnataka SSLC (KSEEB) Science board exam, this chapter typically carries around 4 to 6 marks. Questions usually include 1-mark multiple-choice or reasoning questions, 2-mark definitions or trend explanations (like variation of atomic size across a period), and occasionally a 3-mark application-based question on electronic configuration and group identification.
Frequently Asked Questions
Mendeleev's table was based on atomic mass, which failed to explain the position of isotopes and anomalies like placing heavier elements before lighter ones. Moseley discovered atomic number is a more fundamental property, leading to the Modern Periodic Table.
Mendeleev's table could not accommodate isotopes and had anomalies in atomic masses. Henry Moseley proved that atomic number is a more fundamental property, which resolved these issues in the Modern Periodic Table.
How does atomic radius change down a group and across a period?
Atomic radius increases down a group because new shells are added, increasing the distance from the nucleus. It decreases across a period from left to right because nuclear charge increases, pulling the electrons closer.
What are valence electrons and how do they determine group number?
Valence electrons are the electrons present in the outermost shell of an atom. Elements having the same number of valence electrons belong to the same group in the Modern Periodic Table.
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