Which is incorrect physical property order for the given alkaline earth metals?

Options

A. Metallic radius : `Ba gt Sr gt Ca gt Mg gt Be`
B. Reducing nature : `Ba Sr gt Ca gt Mg gt Be`
C. Density : `Ba gt Sr gt Be gt Mg gt Ca`
D. Negative hydration enthalpy : `Be^(2+) gt Mg^(2+)gt Ca ^(2+)gt Ba^(2+) gt Sr^(2+)`

Answer

To determine the incorrect physical property order for the alkaline earth metals, we will analyze the properties of the alkaline earth metals: beryllium (Be), magnesium (Mg), calcium (Ca), and strontium (Sr).

### Step 1: Understand the Trend in Metallic Radius
The metallic radius of alkaline earth metals increases as we move down the group. This is because additional electron shells are added, which increases the size of the atoms.

- **Order of Metallic Radius**: Be < Mg < Ca < Sr

### Step 2: Analyze Reducing Nature
The reducing nature of alkaline earth metals increases down the group. This is due to the decrease in electronegativity and the increasing ease of losing the outer electrons.

- **Order of Reducing Nature**: Be < Mg < Ca < Sr

### Step 3: Evaluate Density
The density of alkaline earth metals does not follow a simple trend. While beryllium has a lower density than magnesium, as we move down to calcium and strontium, the density increases but not in a straightforward manner.

- **Order of Density**: Be < Mg < Ca < Sr (However, the density of strontium can be less than that of calcium, which may lead to confusion.)

### Step 4: Consider Hydration Enthalpy
Hydration enthalpy is influenced by the charge-to-size ratio. Smaller ions with higher charges have higher hydration enthalpies. Beryllium, being the smallest, has the highest hydration enthalpy, followed by magnesium, calcium, and strontium.

- **Order of Hydration Enthalpy**: Be > Mg > Ca > Sr

### Conclusion
After analyzing these properties, we can conclude that the incorrect order among the alkaline earth metals is related to density. The expected order may not hold true due to the unique properties of these metals.

### Final Answer
The incorrect physical property order for the given alkaline earth metals is related to their density.

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