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Current Question (ID: 18815)

Question:

$\text{The electronic configuration of gadolinium (atomic number of 64) is:}$

Options:

1. $[\text{Xe}] 4f^3 5d^5 6s^2$
2. $[\text{Xe}] 4f^7 5d^2 6s^1$
3. $[\text{Xe}] 4f^7 5d^1 6s^2$
4. $[\text{Xe}] 4f^8 5d^6 6s^2$

Solution:

$\text{Gadolium is a f block element.}$ $\text{The electronic configuration of La (Z=57) is } [\text{Xe}] 5d^1 6s^2.$ $\text{Therefore, further addition of electrons occurs in the lower energy 4f-orbital till it is exactly half-filled at Eu (Z=64).}$ $\text{Thus, the electronic configuration of Eu is } [\text{Xe}] 4f^7 6s^2.$ $\text{Thereafter, addition of next electron does not occur in the more stable exactly half-filled } 4f^7 \text{ shell but occurs in the little higher energy 5d-orbital.}$ $\text{Thus, the electronic configuration of Gd (Z=64) is } [\text{Xe}] 4f^7 5d^1 6s^2.$

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Expected JSON Format:

{
  "question": "The mass of carbon present in 0.5 mole of $\\mathrm{K}_4[\\mathrm{Fe(CN)}_6]$ is:",
  "options": [
    {
      "id": 1,
      "text": "1.8 g"
    },
    {
      "id": 2,
      "text": "18 g"
    },
    {
      "id": 3,
      "text": "3.6 g"
    },
    {
      "id": 4,
      "text": "36 g"
    }
  ],
  "solution": "\\begin{align}\n&\\text{Hint: Mole concept}\\\\\n&1 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\text{ moles of carbon atom}\\\\\n&0.5 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\times 0.5 \\text{ mol} = 3 \\text{ mol}\\\\\n&1 \\text{ mol of carbon} = 12 \\text{ g}\\\\\n&3 \\text{ mol carbon} = 12 \\times 3 = 36 \\text{ g}\\\\\n&\\text{Hence, 36 g mass of carbon present in 0.5 mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6].\n\\end{align}",
  "correct_answer": 4
}