Periodic Law: Elements with similar properties recur at regular intervals when elements are arranged ∈ order of increasing atomic number.
Dobereiner's Triads: Elements with similar properties occur ∈ groups of three, with atomic weights of the middle element being the average of the other two.
Newlands' Law of Octaves: Elements with similar properties recur after every 8th element, similar to the octaves ∈ music.
Mendeleev's Periodic Law: Elements with similar properties have the same valency or the same number of valence electrons.
Periodic Trends: Atomic radius decreases from left to right across a period, and increases down a group.
Metalloids: Elements with properties intermediate between metals and non-metals, located on the border between metals and non-metals ∈ the periodic table.

🪤 The 5 Mistakes That Cost Marks

Not understanding the difference between a period and a group ∈ the periodic table.
Confusing the terms valency and valence electrons.
Not recognizing the relationship between the position of an element ∈ the periodic table and its properties.
Not being able to identify the blocks of the periodic table (s, p, d, f).
Not understanding the concept of metalloids and their position ∈ the periodic table.

✏️ 3 Solved PYQs

Question 1: What is the basis of the modern periodic table? Step 1: The modern periodic table is based on the atomic number of elements. Step 2: The atomic number is the number of protons present ∈ the nucleus of an atom. Step 3: Elements with the same number of protons ∈ their atoms have the same atomic number and are placed ∈ the same group.
Question 2: What is the significance of the periodic table? Step 1: The periodic table helps ∈ the classification of elements. Step 2: It shows the relationship between the position of an element ∈ the periodic table and its properties. Step 3: It helps ∈ the prediction of the properties of an element.
Question 3: What are the advantages of the modern periodic table? Step 1: The modern periodic table is more accurate and reliable. Step 2: It helps ∈ the prediction of the properties of an element. Step 3: It shows the relationship between the position of an element ∈ the periodic table and its properties.

🧠 The One Thing Most Students Get Wrong

The most common mistake students make is not understanding the relationship between the position of an element ∈ the periodic table and its properties.
Students often confuse the terms valency and valence electrons, and do not recognize the significance of the blocks of the periodic table (s, p, d, f).
Understanding the periodic trends, such as the decrease ∈ atomic radius from left to right across a period, and the increase down a group, is crucial for predicting the properties of an element.

👁️ Ayush's Note

To excel ∈ the CBSE Board 2026 exam, it is essential to have a thorough understanding of the periodic classification of elements.
Practice is key, and students should attempt as many questions as possible to reinforce their understanding of the subject.
The periodic table is a powerful tool for predicting the properties of an element, and students should be able to identify the blocks of the periodic table (s, p, d, f) and understand the significance of metalloids.

🔁 Last 5 Minutes Box

Revision of key terms: periodic law, Dobereiner's triads, Newlands' law of octaves, Mendeleev's periodic law.
Quick review of the periodic trends: atomic radius, electronegativity, valency.
Check the position of elements ∈ the periodic table and their properties.
Go through the significant figures and SI units.
Make a mental note of the most common mistakes and how to avoid them.

📝 Practice MCQs

1. What is the basis of the modern periodic table?

A) Atomic mass

B) Atomic number

C) Valency

D) Electron configuration

Answer: B) Atomic number.

2. Which of the following is a metalloid?

A) Sodium

B) Carbon

C) Silicon

D) Oxygen

Answer: C) Silicon.

3. What is the trend ∈ atomic radius down a group?

A) Decreases

B) Increases

C) Remains the same

D) None of the above

Answer: B) Increases.

4. What is the significance of the periodic table?

A) It helps ∈ the classification of elements

B) It shows the relationship between the position of an element ∈ the periodic table and its properties

C) It helps ∈ the prediction of the properties of an element

D) All of the above

Answer: D) All of the above.

5. Which block of the periodic table does the element with atomic number 12 belong to?

A) s-block

B) p-block

C) d-block

D) f-block

Answer: A) s-block.

🚀 Ready to Ace Your Exam?

Put your knowledge to the test! Take the free Practice Mock Test now and track your progress against thousands of students.

🎬 Watch video explanations on YouTube →

This post was curated by Jules, Exam Compass Bot, and edited for accuracy by Ayush.

📚 Related Topics

Continue your revision with these related guides:

Periodic Law: Elements with similar properties recur at regular intervals when elements are arranged ∈ order of increasing atomic number.
Dobereiner's Triads: Elements with similar properties occur ∈ groups of three, with atomic weights of the middle element being the average of the other two.
Newlands' Law of Octaves: Elements with similar properties recur after every 8th element, similar to the octaves ∈ music.
Mendeleev's Periodic Law: Elements with similar properties have the same valency or the same number of valence electrons.
Periodic Trends: Atomic radius decreases from left to right across a period, and increases down a group.
Metalloids: Elements with properties intermediate between metals and non-metals, located on the border between metals and non-metals ∈ the periodic table.