Which of the following pairs are isotopes?
  • Ice and steam
  • Hydrogen and deuterium
  • Nitric oxide and nitrogen dioxide
  • Oxygen and ozone
Why was Thomson’s Model of an atom failed? i. It could not explain the screening of negative charges from that of positive ii. It did not tell about the presence of electrons iii. It did not give an idea about the discrete energy levels iv. It explained the atom as a whole to be electrically neutral Choose the correct option from the following:
  • Both (ii) & (iv)
  • Both (i) & (iii)
  • Only (iii)
  • Only (i)
What property of an element determines its chemical behavior?
  • Valency of an element
  • The molar mass of the element
  • Size of an element
  • None of these
The relative atomic masses of many elements are not whole numbers because:
  • The atoms ionize during the determination of their masses
  • They cannot be determined accurately
  • Presence of impurities
  • Existence of isotopes
Which f the following is not a basic particle of an element?
  • An atom
  • A molecule
  • An ion
  • None
The work function of a metal is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from the metal is approximately:
  • 540nm
  • 400 nm
  • 220 nm
  • 300 nm
The atomic number of an element is 11 ad its mass number isThe correct order representing the number of electrons, protons and neutrons respectively in this atom is:
  • 23, 11, 23
  • 11, 12, 11
  • 11, 11, 12
  • 12, 11, 11
What is an electron?
  • A wave
  • Either of two, depending on how it is observed
  • Neither of these
  • A particle
Which of the following has a charge of +1 and a mass of 1 amu?
  • An electron
  • A helium nucleus
  • A neutron
  • A proton
The isotopes of an element have:
  • Same mass number
  • The same number of neutrons
  • None of these
  • Same atomic number
In an atom valence electron are present in:
  • Anyone of its orbit
  • Next to outermost orbit
  • Outermost orbit
  • First orbit
Which would be the electrical charge on a sulphur atom-containing 18 electrons?
  • \(1^-\)
  • \(2^+\)
  • 0
  • \(2^-\)
Which of the following isotopes is used as the standard for atomic mass?
  • 12 C
  • 13 C
  • 16 O
  • 1 H
In an atom, the constituent electrons:
  • Are uniformly distributed
  • Move around the nucleus in fixed energy levels.
  • Move around the nucleus in a random way.
  • Do not move
Which of the following statements is not correct for Bohr’s model of an atom?
  • The nucleus of an atom is situated at ts center
  • Electrons jump from one orbit to another
  • The electrons move in circular orbits
  • An electron neither loses nor gains energy it jumps from one orbit to another.
A natural phenomenon that supports the experimental conclusion that atoms are divisible is:
  • Allotropy
  • Radioactivity
  • Cracking
  • None of these
The cathode ray experiment was done for the first time by:
  • Goldstein
  • J.J. Thomson
  • Rutherford
  • John Dalton
What is the number of valence electrons of Al?
  • 4
  • 2
  • 3
  • 1
The number of electrons in an element with atomic number X and atomic mass Y will be:
  • (X + Y)
  • X
  • (X - Y)
  • (Y - X)
Which of the following statements is incorrect for cathode rays?
  • They cost shadow of solid objects placed in their path
  • They move in a straight line
  • They get deflected towards positive charge.
  • Their nature depends upon the nature of the gas present in the discharge tube.
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