🛠️ JEE🧪 Chemistry

Structure of Atom

5 solved JEE Chemistry previous year questions on Structure of Atom, each with the correct answer and a full explanation.

Among the following, the correct statement(s) for electrons in an atom is(are)

aUncertainty principle rules out the existence of definite paths for electrons.

bThe energy of an electron in 2s orbital of an atom is lower than the energy of an electron that is infinitely far away from the nucleus.

cAccording to Bohr’s model, the most negative energy value for an electron is given by n = 1, which corresponds to the most stable orbit.

dAccording to Bohr’s model, the magnitude of velocity of electrons increases with increase in values of n.

✓ Correct answer: a) Uncertainty principle rules out the existence of definite paths for electrons.

ExplanationThus, n=1 will have most negative energy According to Bohr's model, an electron in an atom is located at a definite distance from the nucleus and is revolving with a definite velocity around it.According to Heisenberg's principle, it is impossible to determine simultaneously the exact position and momentum (or velocity) of the electron.Uncertainity principle rules out the existence of definite paths or trajectories of electron and other similar particles.Shell or orbit more near to the nucleus has less energy than far away.As we go farther from nucleus, electrons at higher energy levels have more energy.Option D is incorrect as velocity of an electron varies inversely with 'n', hence, when 'n' increases, velocity decreases.

Given below are two statements: Statement-I: The orbitals having same energy are called as degenerate orbitals. Statement-II: In hydrogen atom, 3p and 3d orbitals are not degenerate orbitals. In the light of the above statements, choose the most appropriate answer from the options given

aStatement-I is true but Statement-II is false

bBoth Statement-I and Statement-II are true.

cBoth Statement-I and Statement-II are false

dStatement-I is false but Statement-II is true

✓ Correct answer: a) Statement-I is true but Statement-II is false

ExplanationStatement I is true: orbitals with same energy are called degenerate.Statement II is false: in hydrogen atom, 3s, 3p, 3d orbitals are degenerate because energy depends only on principal quantum number n, not on l. So, correct answer is: Option A — Statement I is true, Statement II is false.

The first use of quantum theory to explain the structure of atom was made by:

aHeisenberg

bBohr

cPlanck

dEinstein

✓ Correct answer: b) Bohr

ExplanationBohr was the first to apply quantum ideas (quantized angular momentum, ) to describe the hydrogen atom’s structure and spectrum.

In a given atom no two electrons can have the same values for all the four quantum numbers. This is called:

aHund's Rule

bAufbau principle

cUncertainty principle

dPauli's Exclusion principle.

✓ Correct answer: d) Pauli's Exclusion principle.

Explanationn a given atom no two electrons can have the same values for all the four quantum numbers.This is called Pauli's exclusion principle.

The number of angular nodes and radial nodes in 3s orbital are [Re-NEET 2020]

a1 and 0, respectively

b3 and 0, respectively

c0 and 1, respectively

d0 and 2, respectively

✓ Correct answer: d) 0 and 2, respectively

ExplanationNumber of angular nodes = .For 3s ( ), angular nodes =0. Number of radial nodes = .For 3s ( , ), radial nodes = .

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