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Current Question (ID: 18808)

Question:
$\text{The } +2 \text{ oxidation state becomes more stable in the first half of the first-row transition elements with increasing atomic number because:}$
Options:
  • 1. $\text{s-Orbital is becoming more and more half-filled.}$
  • 2. $\text{f-Orbital is becoming more and more half-filled.}$
  • 3. $\text{d-Orbital is becoming more and more half-filled.}$
  • 4. $\text{p-Orbital is becoming more and more half-filled.}$
Solution:
$\text{HINT: It is because the d-orbital is becoming more and more half-filled.}$ $\text{STEP 1:}$ $\text{The oxidation states displayed by the first half of the first row of transition metals are given in the table below.}$ $\begin{array}{cccccc} & \text{Sc} & \text{Ti} & \text{V} & \text{Cr} & \text{Mn} \\ +2 & +2 & +2 & +2 & +2 \\ +3 & +3 & +3 & +3 & +3 \\ +4 & +4 & +4 & +4 \\ & +5 & +5 & +6 \\ & & +6 & +7 \end{array}$ $\text{It can be easily observed that except Sc, all other metals display a } +2 \text{ oxidation state. Also, on moving from Sc to Mn, the atomic number increases from 21 to 25.}$ $\text{STEP 2:}$ $\text{This means the number of electrons in the 3d-orbital also increases from 1 to 5.}$ $\text{Sc } (+2) = d^1; \text{Ti } (+2) = d^2; \text{V } (+2) = d^3; \text{Cr } (+2) = d^4 \text{ and Mn } (+2) = d^5$ $+2 \text{ oxidation state is attained by the loss of the two 4s electrons by these metals.}$ $\text{Since the number of d electrons in the } (+2) \text{ state also increases from Ti}(+2) \text{ to Mn}(+2), \text{ the stability of the } +2 \text{ state increases (as d-orbital is becoming more and more half-filled).}$ $\text{Mn } (+2) \text{ has } d^5 \text{ electrons (that is half-filled d shell, which is highly stable)}$

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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
}