Question

Which of the following elements has the highest melting point?
A. $Ba$
B. $Sr$
C. $Ca$
D. $Be$

Answer 1

In order to answer the question, first we have to compare all the optional elements with their properties and then conclude on the basis of their physical and chemical properties that which one has the highest melting point.

Complete answer: Melting point of any element depends on the basis of their size and their polarisation power. If the melting point of any element is higher that means the particular element is in small size and has high polarisation power. And, the size of any element is measured on the basis of their bond lengths. The lattice energy depends on the size of the atom. So, bigger the size of an atom , lesser is its lattice energy and lesser is the melting point.
The atomic number of the following given elements are:
$Ca$ -20, period-4, group-2
$Ba$ -56, period-6, group-2
$Sr$ -38, period-5, group-2
$Be$ -4, period-2, group-2
Since, according to the periodic trend: $Be$ belongs to the lowest period and it has also the least atomic size. So, $Be$ has a larger melting point than others from the options.Or on the other hand, $Be$ has the highest melting point than all other optional elements due to its small size and high polarisation power. When it forms a metal, it means that the bonds are very high energy relative to the atomic size which causes the atoms to be bound tightly. This means it requires more energy (higher temperature) to break the bonds.

Hence, the correct option is (D.) $Be$.

Note: The chemical element with the lowest melting point is Helium and the element with the highest melting point is Carbon. The unity used for the melting point is Celsius (C).