To evaluate the statements provided about the elements Be (Beryllium), Mg (Magnesium), Ca (Calcium), and Sr (Strontium), we need to understand their properties:
- Be (Beryllium): This is a hard and relatively dense metal.
- Mg (Magnesium): This is also a metal but is not as dense as beryllium; it is somewhat less hard, but still considered a metal.
- Ca (Calcium): This is a metal, but it is softer than Be and Mg and less dense.
- Sr (Strontium): This is also a metal and is softer and less dense compared to Ca.
Now, evaluating the statements:
a. All of them are unreactive metalloids.
- False. They are all metals, not metalloids.
b. All of them are hard and dense metals.
- False. While Be is hard and dense, Mg, Ca, and Sr are not categorized as hard and dense.
c. Be and Mg are hard and dense metals and Ca and Sr are unreactive metalloids.
- False. Be and Mg are hard metals, but Ca and Sr are not metalloids; they are metals.
d. Be and Mg are unreactive metalloids and Ca and Sr are hard and dense metals.
- False. Be and Mg are metals, not unreactive metalloids; Ca and Sr are also metals, not classified as hard and dense.
None of the options presented are true. However, if you have to choose or report the best understanding based on usual definitions, b is the least incorrect as it describes metals, albeit not collectively true. But to reiterate: the correct information is that Beryllium and Magnesium are harder and denser compared to Calcium and Strontium, who are softer and less dense. All are metals.