The plum pudding model of the atom, in which electrons are embedded in a sphere of positive charge, was proposed by:
- A.John Dalton
- B.J. J. Thomson
- C.Ernest Rutherford
- D.Niels Bohr
Correct answer
Explanation
The correct answer is B, J. J. Thomson. After discovering the electron in 1897, J. J. Thomson pictured the atom as a sphere of positive charge with negatively charged electrons stuck in it, a picture often compared to plums in a pudding or seeds in a watermelon. It explained why an atom is electrically neutral, but it had no nucleus and could not survive Rutherford's scattering experiment. Option A is wrong because John Dalton's 1808 theory treated the atom as indivisible and offered no internal structure at all. Option C is wrong because Rutherford replaced this model with the nuclear one after the gold foil experiment. Option D is wrong because Niels Bohr then added fixed permitted shells to Rutherford's nucleus in order to explain why the atom is stable.
Read the full article: Atomic Structure and Periodic Table: Models and Trends
Practice Questions
View allWho coined the word 'atom'?
- A.Democritus
- B.Thomson
- C.E Rutherford
- D.John Dalton
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The Greek philosopher Democritus, working in the fifth century before the common era, argued that matter could be divided only up to a limit, and he called that smallest indivisible particle atomos, from which the word atom comes.
Read the full explanation →Who among the following discovered the neutrons?
- A.J. Chadwick
- B.E. Goldstein
- C.Neils Bohr
- D.Ernest Rutherford
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James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha particles and showing that the radiation produced consisted of neutral particles of nearly the same mass as the proton.
Read the full explanation →Rutherford's alpha-particle scattering experiment on a thin gold foil led to which conclusion?
- A.Electrons are embedded in a sphere of positive charge
- B.The atom is indivisible
- C.Electrons revolve in fixed permitted orbits
- D.Almost all the mass and the positive charge lie in a tiny nucleus
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Most alpha particles passed straight through the foil, a few were deflected through small angles and about one in twenty thousand bounced back.
Read the full explanation →The maximum number of electrons that can be accommodated in the M shell is:
- A.8
- B.2
- C.18
- D.32
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The capacity of a shell is given by the formula 2n squared, where n is the number of the shell counted outward from the nucleus.
Read the full explanation →Alkali metals are assigned which group in the Modern Periodic Table?
- A.Second group
- B.Eighteenth group
- C.Third group
- D.First group
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The alkali metals are lithium, sodium, potassium, rubidium, caesium and francium. Each has a single electron in its outermost shell, loses it readily to form a positive ion, and therefore stands in group 1 of the modern periodic table.
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