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Class 9 Journey Inside the Atom worksheet
CBSE Science. Protons, neutrons, electrons, shells, valency, isotopes, average atomic mass. Every sheet has 20 questions in three sections and an answer key, and the numbers change every time.
Sample questions
Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.
Section A · multiple choice
- 1.
How many protons are there in an atom of ¹²₆C?
- 18
- 12
- 13
- 6
Answer
(d) 6
Z = 6, A = 12
- 2.
The valency of calcium (Z = 20) is:
- 2
- 0
- 1
- 3
Answer
(a) 2
configuration 2, 8, 8, 2
- 3.
The electron was discovered by:
- E. Goldstein
- J. Chadwick
- J. J. Thomson
- E. Rutherford
Answer
(c) J. J. Thomson
Section B · short answer
- 4.
Hydrogen has atomic number 1 and mass number 1. Find the numbers of protons, neutrons and electrons in its atom, and write its symbol with A and Z.
Answer
Protons 1, neutrons 0, electrons 1; ¹₁H
neutrons = A − Z
- 5.
Write the distribution of electrons in the shells of magnesium (Z = 12). What is its valency?
Answer
2, 8, 2; valency 2
outer shell has 2 electrons
Section C · long answer
- 6.
Describe Rutherford's alpha-particle scattering experiment and its observations.
Answer
Fast-moving alpha particles were aimed at a very thin gold foil. Most passed straight through; some were deflected by small angles; about one in 12,000 bounced back. He concluded that the atom is mostly empty space, with a tiny, dense, positive nucleus in which almost all its mass is concentrated, and electrons revolving around it.
Fresh sheets for your child
In the app, every Journey Inside the Atom sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.
Coming soon for Android and iPhone.