Understanding Enthalpy of Atomization
Enthalpy of atomization is defined as the energy required to convert one mole of a substance in its standard state into gaseous atoms. For metals, it signifies the strength of the metallic bond holding the atoms together in the solid state. A higher enthalpy of atomization indicates stronger metallic bonding, meaning more energy is needed to break these bonds.
The First Transition Series
The first transition series includes the elements from Scandium (Sc, atomic number Z=21) to Zinc (Zn, atomic number Z=30). These elements are characterized by the gradual filling of the $3d$ atomic orbitals.
- Scandium (Sc)
- Titanium (Ti)
- Vanadium (V)
- Chromium (Cr)
- Manganese (Mn)
- Iron (Fe)
- Cobalt (Co)
- Nickel (Ni)
- Copper (Cu)
- Zinc (Zn)
Factors Influencing Enthalpy of Atomization
The enthalpy of atomization in transition metals is primarily influenced by the strength of metallic bonding, which depends on:
- Number of unpaired d-electrons: A higher number of unpaired $d$-electrons generally leads to stronger metallic bonds due to increased orbital overlap and electron delocalization.
- Contribution of valence electrons: The extent to which both $4s$ and $3d$ electrons participate in the metallic bond.
- Interatomic metallic bonding: The overall strength of attraction between metal atoms in the crystal lattice.
Typically, the enthalpy of atomization increases across the first transition series as the number of unpaired $d$-electrons increases (up to Cr), reaching a maximum, and then generally decreases towards the end of the series (Zn). However, elements like Manganese (Mn) show a dip due to the stability of its half-filled $3d^5$ configuration and possible electron-electron repulsions.
Analyzing the Options Provided: V, Fe, Mn, Cu
Let's compare the electronic configurations and typical enthalpy of atomization values for the specific elements mentioned in the options:
| Element | Electronic Configuration | Number of Unpaired d-electrons | Approx. Enthalpy of Atomization (kJ/mol) |
|---|---|---|---|
| Vanadium (V) | [Ar] $3d^3 4s^2$ | 3 | ~504 |
| Iron (Fe) | [Ar] $3d^6 4s^2$ | 4 | ~416 |
| Manganese (Mn) | [Ar] $3d^5 4s^2$ | 5 | ~285 |
| Copper (Cu) | [Ar] $3d^{10} 4s^1$ | 0 (in d-shell) | ~339 |
Note: While Chromium (Cr) with configuration [Ar] $3d^5 4s^1$ (6 unpaired electrons) usually has the highest enthalpy of atomization in the series (~523 kJ/mol), Vanadium (V) shows a very high value due to effective metallic bonding.
Conclusion on Highest Enthalpy of Atomization
Comparing the provided options, Vanadium (V) has the highest enthalpy of atomization (~504 kJ/mol). Iron (Fe) follows with ~416 kJ/mol. Manganese (Mn) has a significantly lower value (~285 kJ/mol) than expected from its unpaired electrons, and Copper (Cu) also has a moderate value (~339 kJ/mol), partly due to its filled $d$-shell.
Important Questions from Miscellaneous
- An electromagnetic wave with its magnetic field $B = 0.3\cos(ky-10^8t)i$ tesla is propagating in a non-magnetic dielectric medium of refractive index 2. The wavelength of the wave is
For a given system of resistors having resistances R, 2R, R$_0$ and 2R (shown in the figure), what will be the value of resistance of the resistor R$_0$, when there is NO current in the galvanometer G?
- A cyclotron has an oscillator frequency of $12\times10^6$ Hz and 'Dee' radius of 21 inches. The value of magnetic induction (field) needed to accelerate a deuteron (mass = $3.34 \times 10^{-27}$ kg and charge = $1.6\times10^{-19}$ C) is
- When white light propagating in air passes through a glass prism, it splits into a band of colours referred to as the white light spectrum. This phenomenon is called the dispersion of light. Among the following colours, the angle of deviation will be the highest in
- Why do we prefer to have a liquid and not a gas to be used as the fluid in a hydraulic machine?
