Chapter 4: Structure of the Atom
Learning Notes (Set 2) for Class 9 Science
Exam oriented Study Guide for CBSE Class 9 Science
Here are 10 quick question-and-answer notes to help you revise the key concepts from the chapter on Structure of the Atom. Use these for a quick study session before your exam!
Question 1: Who discovered the presence of positively charged canal rays?
Answer: E. Goldstein discovered the presence of canal rays in a gas discharge experiment.
Question 2: What are the key properties of a proton?
Answer: A proton is a positively charged subatomic particle with a mass of approximately one unit.
SOURCE: WWW.QUIZNEST.INQuestion 3: What are the characteristics of a neutron?
Answer: A neutron is a subatomic particle with no charge and a mass nearly equal to that of a proton.
You are on Chapter 4: Structure of the Atom (Learning Notes for Class 9 Science) Set 2
Question 4: What was the main feature of Thomson's "Plum Pudding" model of the atom?
Answer: The model suggested that an atom is a positively charged sphere with electrons embedded in it.
Question 5: What did Rutherford's alpha-particle scattering experiment conclude about the space inside an atom?
Answer: The experiment showed that most of the space inside an atom is empty, as most alpha particles passed straight through the gold foil.
Question 6: Why did Rutherford's model fail to explain the stability of the atom?
Answer: The model failed because, according to classical physics, a revolving electron would lose energy and eventually fall into the nucleus.
SOURCE: WWW.QUIZNEST.INQuestion 7: What is the definition of valency?
Answer: Valency is the combining capacity of an atom, determined by the number of electrons in its outermost shell.
Question 8: What is the maximum number of electrons an L-shell can accommodate?
Answer: The L-shell, which is the second orbit (n=2), can accommodate a maximum of 8 electrons (2n2 = 2(2)2 = 8).
You are on Chapter 4: Structure of the Atom (Learning Notes for Class 9 Science) Set 2
Question 9: What is the rule of octet?
Answer: An atom is considered stable when it has eight electrons in its outermost shell, which it tries to achieve by gaining, losing, or sharing electrons.
Question 10: What is the difference between isotopes and isobars?
Answer: Isotopes have the same atomic number but different mass numbers, while isobars have the same mass number but different atomic numbers.
SOURCE: WWW.QUIZNEST.IN
