Exams › JEE Main › Chemistry
Which of the following pair is not isoelectronic species? (At. no. Sm, 62; Er, 68; Yb, 70; Lu, 71; Eu, 63; Tb, 65; Tm, 69)
- Sm2+ and Er3+
- Yb2+ and Lu
- Eu2+ and Tb4+
- Tb2+ and Tm4+
Correct answer: Tb2+ and Tm4+
Solution
Tb2+ and Tm4+ are not isoelectronic because they have different numbers of electrons; Tb2+ has 58 electrons while Tm4+ has 65 electrons, resulting in different electronic configurations.
Related JEE Main Chemistry questions
- At what wavenumber does the first line of the hydrogen Balmer series occur in the atomic spectrum?
- In the hydrogen emission spectrum, a spectral series has its limit at 12186.3 cm$^{-1}$. This series is identified as
- Two rapidly moving particles X and Y have de Broglie wavelengths of 1 nm and 4 nm, respectively. If the mass of X is nine times the mass of Y, what is the ratio of their kinetic energies, X:Y?
- Given that Planck’s constant is $6.63 \times 10^{-34}$ J s and the speed of light is $3.0 \times 10^8$ m s$^{-1}$, which of the following is nearest to the wavelength, in nanometres, of light having frequency $8 \times 10^{15}$ s$^{-1}$?
- A lithium ion and a proton are each accelerated through the same potential difference. If their de Broglie wavelengths are $\lambda_1$ and $\lambda_2$, respectively, and $m_{\text{Li}} = 9m_p$, what is the ratio $\lambda_1 : \lambda_2$?
- If the uncertainties in position and momentum are the same, what is the uncertainty in velocity?
⚔️ Practice JEE Main Chemistry free + battle 1v1 →