Chemistry Multiple Choice Questions on “Atomic Models”.
1. What is the absolute charge of a proton?
a) +1.602176×10-27
b) –1.602176×10-19
c) +1.602176×10-19
d) –1.602176×10-27
Answer: b
Clarification: According to the fundamental properties of particles, protons charge is +1.602176×10-19C. It is a subatomic particle. Rutherford discovered protons. Its elementary charge is 1. Proton’s charge is positive.
2. Which of the following models are not the same as Thomson Model of Atom?
a) plum pudding model
b) watermelon model
c) raisin pudding model
d) nuclear model
Answer: d
Clarification: Thomson proposed a model of the atom, in which electrons are embedded to make it as the stable electrostatic arrangement and such that positive charge is equally distributed around a sphere. Mass is assumed to be equally distributed. So. it has different names like plum pudding, watermelon and raisin pudding model.
3. Elements do emit radiation on their own and this property is known as _____
a) Radioactivity
b) Refraction
c) Absorption
d) Adsorption
Answer: a
Clarification: Henri Becquerel discovered that elements emit radiation and termed this phenomenon as radioactivity. Later Curie on research found out about α-rays, β-rays and γ-rays. Later Rutherford concluded that α particles are helium nuclei.
4. Which of the following statements you think is wrong regarding α particle scattering effect?
a) α particles mostly move through the gold foil having zero deflection
b) A small fraction are deflected
c) One in Twenty Thousand turns 180°
d) The thickness of the gold foil is about 100μm
Answer: d
Clarification: In this effect, a thin foil (thickness 100nm) made up of gold and coated with fluorescent ZnS screen which is circular around it. α particles mostly move through the gold foil having zero deflection, a small fraction is deflected and one in twenty thousand turns 180°.
5. If the number of protons and neutrons of an element is 13 and 14 respectively, then what’s the atomic number(Z) and mass number(A)?
a) 13, 13
b) 13, 27
c) 14, 13
d) 27, 14
Answer: b
Clarification: For an element, Atomic number(Z) = number of protons in that atoms = numbers of electrons in that atom; Mass number = number of protons + number of neutrons. So Z = 13 and A = 13 + 14 = 27. Hence that element is Aluminium.
6. Which of the following is not an isotope of hydrogen?
a) protium
b) deuterium
c) tritium
d) helium
Answer: d
Clarification: Protium has only 1 proton, deuterium has one proton and 1 neutron whereas tritium has one proton and two neutrons. They are represented by 1H1, 1D2 and 1T3. Helium has 2 protons and two neutrons, hence can’t consider as an isotope. Isotope means having the same number of protons but differ in the number of neutrons.
7. Chemical properties of an atom are dependent on a number of electrons in that particular atom.
a) True
b) False
Answer: a
Clarification: Yes, chemical properties of an atom is dependent on a number of electrons in that particular atom, which in turn is decided by the number of protons present in that atom. The number of neutrons has only a small effect on this.
8. Find out the number of neutrons, protons, and electrons of 17Cl37 respectively.
a) 20, 20, 17
b) 17, 17, 20
c) 20, 17, 17
d) 17, 17, 17
Answer: c
Clarification: An atom is written in the symbol ZXA. By comparing it to 17Cl37, we get a number of protons as 17 and mass number as 37. Mass number – proton number = neutron number. Number of neutrons is 37 – 17 = 20. No. of protons = No. of electrons = 17.
9. Pick out the isobar of 18Ar40.
a) 12Mg24
b) 26Fe58
c) 19K40
d) 28Ni64
Answer: c
Clarification: Isobar is a species of an element having the same mass number but a different atomic number. As per the above question, only 19K40 satisfies the conditions of 18Ar40 to be its isotope.
10. Gravitational force = Gm1m2/r2.
a) True
b) False
Answer: a
Clarification: The formula of gravitational force is given by Gm1m2/r2. Here G is the gravitational constant, while m1 and m2 are the masses and r is the distance between m1 and m2. This theory is formulated when classic mechanics is applied to it.