Test: Atomic Models - Chemistry MCQ

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.

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°.

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.

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.

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.

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.

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.

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.

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.

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.