#1
Who proposed the first atomic theory?
Democritus
ExplanationDemocritus proposed the idea of indivisible particles called atoms.
#2
What is the primary factor that differentiates isotopes of an element?
Number of neutrons
ExplanationIsotopes of an element have the same number of protons but different numbers of neutrons.
#3
What is the primary force that holds the nucleus of an atom together?
Nuclear force
ExplanationThe nuclear force binds protons and neutrons in the nucleus despite their electrostatic repulsion.
#4
In the context of atomic theory, what does the term 'quantum leap' refer to?
Sudden change in the energy levels of electrons
ExplanationA quantum leap refers to an electron moving between energy levels in an atom, emitting or absorbing energy.
#5
What is the fundamental concept of Dalton's atomic theory?
Atoms are indivisible and indestructible.
ExplanationDalton's theory states that atoms cannot be divided or destroyed.
#6
Who discovered the electron and proposed the 'plum pudding' model of the atom?
J.J. Thomson
ExplanationJ.J. Thomson discovered electrons and proposed a model where they were embedded in a positively charged sphere.
#7
What is the name of the experiment conducted by Rutherford that led to the discovery of the atomic nucleus?
Gold foil experiment
ExplanationRutherford's gold foil experiment showed that the atom is mostly empty space with a dense central nucleus.
#8
Which of the following elements did Mendeleev leave gaps for in his periodic table, predicting the existence of undiscovered elements?
Germanium
ExplanationMendeleev predicted the properties of missing elements, like Germanium, based on the periodic trends of known elements.
#9
Who proposed the concept of the neutron as a neutral subatomic particle in the nucleus?
Chadwick
ExplanationChadwick discovered the neutron, which contributes to the nucleus's mass without a charge.
#10
Which scientist proposed the concept of the wave-particle duality of electrons?
Louis de Broglie
ExplanationDe Broglie suggested that particles like electrons exhibit both wave-like and particle-like behavior.
#11
Which scientist developed the planetary model of the atom with electrons orbiting the nucleus in specific energy levels?
Niels Bohr
ExplanationNiels Bohr proposed a model where electrons orbit the nucleus in discrete energy levels.
#12
Who proposed the uncertainty principle, stating that it is impossible to simultaneously know the exact position and momentum of a particle?
Werner Heisenberg
ExplanationHeisenberg introduced the concept that the more precisely the position of a particle is determined, the less precisely its momentum can be known.
#13
In Bohr's model of the atom, what is the significance of electrons residing in specific energy levels or orbits?
It explains the quantization of energy levels.
ExplanationBohr's model explains how electrons can only exist in certain energy levels, explaining the discrete lines in atomic spectra.
#14
Which scientist introduced the concept of quantum numbers and the quantum mechanical model of the atom?
Erwin Schrödinger
ExplanationSchrödinger formulated an equation describing the behavior of electrons in atoms using quantum numbers.
#15
Which of the following elements was the first to be artificially synthesized by scientists?
Technetium
ExplanationTechnetium was the first element to be artificially produced, filling a gap in the periodic table.
#16
What is the modern understanding of the electron cloud or orbital in an atom?
Region where an electron is likely to be found
ExplanationElectron cloud represents the probability distribution of finding an electron around the nucleus.