Identify the correct order in which the covalent radius of the following elements increases (I)…

Identify the correct order in which the covalent radius of the following elements increases (I) $\mathrm{Ti}$$\quad$(II) $\mathrm{Ca}$$\quad$(III) Sc
  1. (I), $\quad$ (II), $\quad$ (III)
  2. (III), $\quad$ (II), $\quad$ (I)
  3. $\begin{array}{lll}(\mathrm{II}), & \text { (I) }, \quad \text { (III) }\end{array}$
  4. (I), $\quad$(III), $\quad$(II)

Solution

$\begin{aligned} & { }_{20} \mathrm{Ca}=[\mathrm{Ar}] 4 s^2 \\ & { }_{21} \mathrm{Sc}=[\mathrm{Ar}] 4 s^2, 3 d^1 \\ & { }_{22} \mathrm{Ti}=[\mathrm{Ar}] 4 s^2, 3 d^2 \end{aligned}$ As $d$-orbital have diffused shape, hence their electron shields nuclear charge upto lesser extent. Hence, due to increase in effective nuclear charge $\left(Z_{\text {eff }}\right)$, atomic size decrease, in the following order, $\mathrm{Ca}>\mathrm{Sc}>\mathrm{Ti}$

Asked in: AP EAMCET 2005

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