D & F Block Elements MCQs for NEET — Chemistry Questions with Answers

The context (MAGNETISM_AND_MATTER, Figure 5.7 and accompanying text on page 147) states: 'Figure 5.7(a) shows a bar of diamagnetic material placed in an external magnetic field. The field lines are repelled or expelled and the field inside the material is reduced.'

While the text (The d - and f - Block Elements, page 102) states that for the first series transition metals the contribution of the orbital angular momentum is effectively quenched, Table 4.7 shows slight discrepancies between 'Calculated' and 'Observed' magnetic moments. These small differences are often attributed to the incomplete quenching of orbital angular momentum in some cases, or other complex interactions not accounted for by the simple 'spin-only' formula, which considers only spin contribution. The question from coordination compounds 5.7: '[Fe(H2O)6]3+ is strongly paramagnetic whereas [Fe(CN)6]3– is weakly paramagnetic. Explain.' highlights that environmental factors can influence magnetic properties.

The text (MAGNETISM_AND_MATTER, page 148, and page 152 summary point 6) states: 'Diamagnetism is present in all the substances. However, the effect is so weak in most cases that it gets shifted by other effects like paramagnetism, ferromagnetism, etc.' and 'Diamagnetism is universal. It is present in all materials. But it is weak and hard to detect if the substance is para- or ferromagnetic.'

The text explains (MAGNETISM_AND_MATTER, page 148): 'When magnetic field is applied, those electrons having orbital magnetic moment in the same direction slow down and those in the opposite direction speed up. This happens due to induced current in accordance with Lenz’s law...'

According to IUPAC, transition metals are defined as metals which have incomplete d subshell either in neutral atom or in their ions. Zinc (Z=30) has a full $3d^{10}$ configuration in its ground state as well as in its common oxidation states, and therefore is not regarded as a transition metal. Scandium (Z=21) has $3d^1$, Chromium (Z=24) has $3d^5$, and Copper (Z=29) has $3d^{10}$ (with $4s^1$), making their d-subshells incompletely filled in their elemental or common ionic states.

For $n=4$, the outer electronic configuration is $3d^24s^2$. The principal quantum number 'n' represents the period, so the element is in Period 4. The sum of electrons in the $(n-1)d$ and $ns$ orbitals gives the group number for d-block elements. Here, $2 (d) + 2 (s) = 4$. Thus, it is in Group 4. This corresponds to Titanium (Ti, Z=22).

The electronic configurations of Cr and Cu show exceptions due to the extra stability of half-filled ($d^5$) and completely filled ($d^{10}$) d-orbitals. Cr (Z=24) has the configuration $3d^54s^1$ instead of $3d^44s^2$. Cu (Z=29) has the configuration $3d^{10}4s^1$ instead of $3d^94s^2$. This is because the energy gap between the 3d and 4s orbitals is small enough to allow this electron promotion.

The outermost electronic configuration is $7s^1$. Elements ending in 's' orbitals are s-block elements. The number of electrons in the outermost 's' orbital determines the group for s-block elements. Since there is 1 electron in the $7s$ orbital, it belongs to Group 1. This configuration corresponds to Francium (Fr, Z=87).

Helium strictly belongs to the s-block as its configuration is $1s^2$. However, its positioning in the p-block (Group 18) along with other noble gases is justified because it has a completely filled valence shell ($1s^2$) and exhibits properties characteristic of other noble gases. Hydrogen, with $1s^1$, can be placed in Group 1 (alkali metals) or Group 17 (halogens) due to its ability to lose or gain an electron, respectively.

P-block elements are characterized by the filling of p-orbitals. Their general outer electronic configuration ranges from $ns^2np^1$ (Group 13) to $ns^2np^6$ (Group 18), excluding Helium which is an exception placed in Group 18.