Who among the following discovered the neutrons?
- A.J. Chadwick
- B.E. Goldstein
- C.Neils Bohr
- D.Ernest Rutherford
Correct answer
Explanation
The correct answer is A, J. Chadwick. 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. The discovery explained why the mass of an atom is greater than the mass of its protons and electrons together. Option B is wrong because E. Goldstein discovered canal rays, which carried positive charge and led to the identification of the proton. Option C is wrong because Niels Bohr gave the model in which electrons revolve in fixed permitted shells without radiating energy. Option D is wrong because Ernest Rutherford discovered the nucleus through alpha-particle scattering and had only predicted that a neutral particle should exist. Note the years, which papers like to ask together: the electron in 1897, the nucleus in 1911 and the neutron in 1932, the last of the three fundamental particles to be found.
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 →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.
Read the full explanation →Which of the following elements has the highest electronegativity?
- A.Fluorine
- B.Bromine
- C.Iodine
- D.Chlorine
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Electronegativity is the tendency of an atom to attract a shared pair of electrons towards itself. It increases from left to right across a period, as nuclear charge grows, and decreases down a group, as each new shell puts the outer electrons further from the nucleus.
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