Which of the following pairs is not isoelectronic species? (At. no. Sm, 62; Er, 68; Yb, 70; Lu, 71; Eu, 63; Tb, 65; Tm, 69)
- \(Sm^{2+} \space and \space Er^{3+}\)
- \(Yb^{2+} \space and \space Lu^{3+}\)
\(Eu^{2+} \space and \space Tb^{4+}\)
- \(Tb^{2+} \space and \space Tm^{4+}\)
The Correct Option is A, D
Solution and Explanation
Top JEE Main Chemistry Questions
- A D-aldotetrose on oxidation with concentrated \(HNO_3\) resulted in optically inactive dicarboxylic acid. The structure of the D-aldotetrose is:
- JEE Main - 2026
- Chemistry
- Carbohydrates
- Statement I: For an ideal gas, heat capacity at constant volume is always greater than the heat capacity at constant pressure.
Statement II: In a constant volume process, no work is produced and all the heat withdrawn goes into the chaotic motion and is reflected by a temperature increase of the ideal gas.
In the light of the above statements, choose the correct answer:- JEE Main - 2026
- Chemistry
- The Kinetic Theory of Gases
\(t_{100\%}\) is the time required for 100% completion of a reaction, while \(t_{1/2}\) is the time required for 50% completion of the reaction. Which of the following correctly represents the relation between \(t_{100\%}\) and \(t_{1/2}\) for zero order and first order reactions respectively
- JEE Main - 2026
- Chemistry
- Zero-order Reactions
One mole of an alkane (\(x\)) requires 8 mole oxygen for complete combustion. Sum of number of carbon and hydrogen atoms in the alkane (\(x\)) is ______.
- JEE Main - 2026
- Chemistry
- Hydrocarbons
For reaction \(A \rightarrow P\), rate constant \(k = 1.5 \times 10^3\ s^{-1}\) at \(27^\circ C\). If activation energy for the above reaction is \(60\ kJ\ mol^{-1}\), then the temperature (in \(^{\circ}C\)) at which rate constant \(k = 4.5 \times 10^3\ s^{-1}\) is ______. (Nearest integer) \[ \text{Given: } \log 2 = 0.30,\ \log 3 = 0.48,\ R = 8.3\ J\ K^{-1}\ mol^{-1},\ \ln 10 = 2.3 \]
- JEE Main - 2026
- Chemistry
- Activation energy
Top JEE Main Structure of atom Questions
- Consider the last electron of an element having atomic number $9$ and choose the correct option.
- JEE Main - 2025
- Chemistry
- Structure of atom
- Wavenumber for a radiation having $5800 \, \mathring{A}$ wavelength is $x \times 10 \, \text{cm}^{-1}$. The value of $x$ is _________
- JEE Main - 2024
- Chemistry
- Structure of atom
- In case of isoelectronic species the size of \(F^-\), \(Na\) and \(Na^+\) is affected by:
- JEE Main - 2024
- Chemistry
- Structure of atom
Which transition in the hydrogen spectrum would have the same wavelength as the Balmer type transition from $n =4$ to $n =2$ of $He ^{+}$spectrum
- JEE Main - 2023
- Chemistry
- Structure of atom
Arrange the following orbitals in decreasing order of energy
A. $n=3, l =0, m =0$
B. $n =4, l =0, m =0$
C. $n =3, l =1, m =0$
D. $n =3, l =2, m =1$
The correct option for the order is :- JEE Main - 2023
- Chemistry
- Structure of atom
Top JEE Main Questions
- Let $A = \begin{bmatrix} -1 & 1 & -1 \\ 1 & 0 & 1 \\ 0 & 0 & 1 \end{bmatrix}$ satisfy $A^2 + \alpha(\text{adj}(\text{adj}(A))) + \beta(\text{adj}(A)(\text{adj}(\text{adj}(A)))) = \begin{bmatrix} 2 & -2 & 2 \\ -2 & 0 & -1 \\ 0 & 0 & -1 \end{bmatrix}$ for some $\alpha, \beta \in \mathbb{R}$.
Then $(\alpha - \beta)^2$ is equal to __________.- JEE Main - 2026
- Algebra
- If the mean of the following grouped data is \(21\):
then \(k\) is one of the roots of the equation:- JEE Main - 2026
- Arithmetic Mean
- In a screw gauge the zero of main scale reference line coincides with the fifth division of the circular scale when two studs are in contact. There are 100 divisions in circular scale and pitch of screw gauge is 0.1 mm. When diameter of a sphere is measured, the reading of main scale is 5 mm and 50th division of circular scale coincides with the reference line of main scale. The diameter of sphere is _______ mm.}
- JEE Main - 2026
- Units, Dimensions and Measurements
- A D-aldotetrose on oxidation with concentrated \(HNO_3\) resulted in optically inactive dicarboxylic acid. The structure of the D-aldotetrose is:
- JEE Main - 2026
- Carbohydrates
- Statement I: For an ideal gas, heat capacity at constant volume is always greater than the heat capacity at constant pressure.
Statement II: In a constant volume process, no work is produced and all the heat withdrawn goes into the chaotic motion and is reflected by a temperature increase of the ideal gas.
In the light of the above statements, choose the correct answer:- JEE Main - 2026
- The Kinetic Theory of Gases
Concepts Used:
Structure of Atom
Atomic Structure:
The atomic structure of an element refers to the constitution of its nucleus and the arrangement of the electrons around it. Primarily, the atomic structure of matter is made up of protons, electrons and neutrons.
Dalton’s Atomic Theory
Dalton proposed that every matter is composed of atoms that are indivisible and indestructible.
The following are the postulates of his theory:
- Every matter is made up of atoms.
- Atoms are indivisible.
- Specific elements have only one type of atoms in them.
- Each atom has its own constant mass that varies from element to element.
- Atoms undergo rearrangement during a chemical reaction.
- Atoms can neither be created nor be destroyed but can be transformed from one form to another.
Cons of Dalton’s Atomic Theory
- The theory was unable to explain the existence of isotopes.
- Nothing about the structure of atom was appropriately explained.
- Later, the scientists discovered particles inside the atom that proved, the atoms are divisible.
Subatomic Particles
- Protons - are positively charged subatomic particles.
- Electron - are negatively charged subatomic particles.
- Neutrons - are electrically neutral particles and carry no charge
Atomic Structure of Isotopes
Several atomic structures of an element can exist, which differ in the total number of nucleons.These variants of elements having a different nucleon number (also known as the mass number) are called isotopes of the element. Therefore, the isotopes of an element have the same number of protons but differ in the number of neutrons. For example, there exist three known naturally occurring isotopes of hydrogen, namely, protium, deuterium, and tritium.