Chapter 8
Journey Inside the Atom
CBSE Class 9
Science Solutions
Educart Science class Class 9 NCERT Exemplar cover
Question:

Why did Thomson conclude that electrons are present in all atoms? [Pg. No. 143]

Answer: Verified

Thomson concluded that electrons are present in all atoms from his cathode ray experiment. He observed that cathode rays were made of negatively charged particles and their properties remained the same even when different gases were used in the discharge tube or different metals were used for the electrodes. This showed that these negatively charged particles were not specific to any one substance. Therefore, Thomson concluded that electrons are common subatomic particles present in atoms of all elements.

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More NCERT Questions
Identify the number of electrons in the outermost shell of the following elements: (A) 612C(B) 919F(C) 1428Si [Pg. No. 152] If a bromine atom is available in the form of, say two isotopes, 3579Br (49.7\%) and 3581Br (50.3\%), calculate the average atomic mass of the bromine atom. [Pg. No. 156] Write the electronic configuration of the elements having atomic numbers 12, 16 and 18. [Pg. No. 152] Two different atoms have 11 protons each, but one has 12 neutrons, and the other has 13 neutrons. How do their atomic numbers and mass numbers compare? Are they the same element or different elements?