Q (1): Assertion: Valency of fluorine is one.
Reason: Fluorine atom contain seven valence electrons.
Q (2): Assertion : The size of the nucleus is very small as compared to the size of the atom.
Reason : The electrons revolve around the nucleus of the atom
Q (3): Assertion : Thomson’s atomic model is known as ‘raisin pudding’ model.
Reason : The atom is visualized as a pudding of positive charge with electrons (raisins) embedded in it.
Q (4): Assertion : Electrons moving in the same orbit will lose or gain energy.
Reason : On jumping from higher to lower energy level, the electron will gain energy.
Q (5): Assertion : A few positively charged a -particles are deflected in Rutherford’s experiment.
Reason : Most of the space in the atom is empty
Q (6): Assertion : Isotopes are electrically neutral.
Reason : Isotopes are species with same mass number but different atomic numbers
Q (7): Assertion : Isotopes are electrically neutral.
Reason : Isotopes of an element have equal number of protons and electrons
Q (8): Assertion : In Rutherford’s gold foil experiment, very few a -particles are deflected back.
Reason : Nucleus present inside the atom is heavy
Q (9): Assertion : Isobars are identical in chemical properties.
Reason : Isobars have same mass number.
Q (10): Assertion : Anions are larger in size than the parent atom.
Reason : In an anion, the number of protons in the nucleus is less than the number of electrons moving around it.
Q (11): Assertion : Isotopes of an element show different valencies .
Reason : Isotopes have different atomic numbers
Q (12): Assertion : The atoms of different elements having same mass number but different atomic numbers are known as isobars.
Reason : The sum of protons and neutrons, in the isobars is always different.
Q (13): Assertion : For noble gases, valency is zero.
Reason : Noble gases have 8 valence electrons.
Q (14): Assertion : The mass of the total number of proton sand neutrons is a measure of the approximate mass of an atom.
Reason : The mass of an electron is negligible.
Q (15): Assertion : Bohr’s orbits are called stationary orbits.
Reason : Electrons remain stationary in these orbits for some time.
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