4. Structure of The Atom Class 9 Science [LATEST] Solutions Chapter Review in English - CBSE Study
NCERT Solutions for Class 9 Science are carefully prepared according to the latest CBSE syllabus and NCERT textbooks to help students understand every concept clearly. These solutions cover all important 4. Structure of The Atom with detailed explanations and step-by-step answers for better exam preparation. Each Chapter Review is explained in simple language so that students can easily grasp the fundamentals and improve their academic performance. The study material is designed to support daily homework, revision practice, and final exam preparation for Class 9 students. With accurate answers, concept clarity, and structured content, these NCERT solutions help learners build confidence and score higher marks in their examinations. Whether you are revising a specific topic or preparing an entire chapter, this resource provides reliable and syllabus-based guidance for complete success in Science.
Class 9 English Medium Science All Chapters:
4. Structure of The Atom
1. Chapter Review
Chapter Review:
- Atoms and molecules are the fundamental building blocks of matter.
- The existence of different kinds of matter is due to different atoms constituting them.
- The electron is identified by J.J. Thomson.
- Electrons, protons and nutrons are sub atomic particles.
- E. Goldstein in 1886 discovered the presence of new radiations in a gas discharge and called them canal rays.
- Electrons carry Negative (-) charge.
- Protons carry Positive (+) charge.
- Nutrons carry No any charge.
- J.J. Thomson was the first one to propose a model for the structure of an atom.
- The electrons revolve around the nucleus in well-defined orbits.
- The size of the nucleus is very small as compared to the size of the atom.
- Protons and Nutrons are situated in nucleus of atom.
- Orbits or shells of an atom are represented by the letters K, L, M, and N.
- J. Chadwick discovered another sub atomic particles named nutron.
- The number of protons present in nucleus of an atom is known as atomic number. i.e Atomic mass = total number of protons in nucleus os an atom.
- The sum of the masses of protons and neutrons present in the nucleus is known as Atomic Mass.
- The maximum number of electrons present in a shell is given by the formulla 2n2.
- The electrons present in the outermost shell of an atom are known as the valence electrons.
- The number of valence electrons present in outer most shell of an atom is known as its valency.
- The mass number is defined as the sum of the total number of protons and
neutrons present in the nucleus of an atom. - The atoms of the same element, having the same atomic number but differentmass numbers is called its isotopes.
- Protium, Deuterium and tritium are isotopes of Hydrogen.
- Many elements consist of a mixture of isotopes. Each isotope of an element is a pure substance.
- The chemical properties of isotopes are similar but their physical properties are different.
- An isotope of uranium is used as a fuel in nuclear reactors.
- An isotope of cobalt is used in the treatment of cancer.
- An isotope of iodine is used in the treatment of goitre.
- Atoms of different elements with different atomic numbers, which have the same mass number, are known as isobars.
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