Periodic Table and Periodicity is one of the most important chapters of Class 9 Chemistry. It helps students understand how elements are arranged and how their properties change in a regular pattern. The Modern Periodic Table is based on atomic number and shows clear trends in properties like atomic size, ionization energy, and electronegativity. This chapter is very important for exams because many MCQs, short questions, and conceptual questions are asked from it.
Modern Periodic Table
The Modern Periodic Table is a systematic arrangement of elements based on their atomic number. Elements are arranged in horizontal rows called periods and vertical columns called groups. This arrangement helps in understanding similarities and differences in element properties.
Salient Features of Modern Periodic Table
The Modern Periodic Table has several key features that make it easy to study:
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Elements are arranged according to increasing atomic number
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There are 7 periods and 18 groups
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Elements in the same group have similar properties
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Metals are on the left side, non-metals on the right side
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Metalloids are present between metals and non-metals
These features help students easily understand chemical behavior and trends.
Variation of Periodic Properties in Periods and Groups
Periodic properties change in a regular pattern across periods and down groups:
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Atomic Size: Decreases across a period and increases down a group
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Ionization Energy: Increases across a period and decreases down a group
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Electronegativity: Increases across a period and decreases down a group
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Electron Affinity: Generally increases across a period and decreases down a group
Understanding these trends helps in predicting the behavior of elements and is very important for exams.
📥 Download Chapter 8 Notes – Periodic Table and Periodicity (PDF)
Get complete Class 9 Chemistry Chapter 8 Periodic Table and Periodicity Notes according to the 2026 new syllabus. These notes are specially designed for students to easily understand concepts and prepare effectively for exams.
Skip to PDF contentWhat’s included in these notes?
✔ Modern Periodic Table explanation
✔ Salient features (important points)
✔ Periodic trends (Atomic size, Ionization energy, Electronegativity, Electron affinity)
✔ Exam-focused explanations
✔ Easy language for quick revision
⬇ Download Chapter 8 Notes (PDF)
❓ Frequently Asked Questions (FAQs)
1. What is the Modern Periodic Table?
The Modern Periodic Table is an arrangement of elements based on their atomic number. It helps in understanding the properties and behavior of elements in a systematic way.
2. How many periods and groups are in the Modern Periodic Table?
There are 7 periods (horizontal rows) and 18 groups (vertical columns) in the Modern Periodic Table.
3. What is periodicity in chemistry?
Periodicity refers to the repeating pattern of physical and chemical properties of elements when they are arranged in order of increasing atomic number.
4. How does atomic size change in the periodic table?
Atomic size decreases across a period and increases down a group due to changes in nuclear charge and number of electron shells.
Chapter 8 – Periodic Table and Periodicity | MCQs
1. Modern Periodic Table is arranged on the basis of:
(a) Atomic Mass
(b) Atomic Number ✅
(c) Valency
(d) Reactivity
2. Horizontal rows in the Periodic Table are called:
(a) Groups
(b) Periods ✅
(c) Families
(d) Series
3. Vertical columns in the Periodic Table are called:
(a) Series
(b) Periods
(c) Groups ✅
(d) Rows
4. Which element has the highest electronegativity in a period?
(a) Alkali metals
(b) Halogens ✅
(c) Noble gases
(d) Alkaline earth metals
5. Atomic size generally _____ across a period and _____ down a group.
(a) Increases, decreases
(b) Decreases, increases ✅
(c) Increases, increases
(d) Decreases, decreases
6. Ionization energy _____ across a period and _____ down a group.
(a) Decreases, increases
(b) Increases, decreases ✅
(c) Increases, increases
(d) Decreases, decreases