Beryllium's small size and high ionization energy result in stronger metallic bonding and a higher melting point compared to other alkaline earth metals. As you move down the group from beryllium to radium, the atomic radii of the elements increase, and the ionization energies decrease. This leads to weaker metallic bonding and lower melting points.

In addition, beryllium has a relatively high boiling point because of its high ionization energy. The ionization energy is the energy required to remove an electron from an atom. The higher the ionization energy, the stronger the attraction between the nucleus and the electrons. This strong attraction makes it more difficult to separate the electrons from the nucleus, which results in a higher boiling point.

Here's a table summarizing the melting points and boiling points of the alkaline earth metals:

| Element | Melting Point (°C) | Boiling Point (°C) |

|---|---|---|

| Beryllium | 1,287 | 2,477 |

| Magnesium | 650 | 1,090 |

| Calcium | 842 | 1,484 |

| Strontium | 768 | 1,382 |

| Barium | 727 | 1,640 |

| Radium | 973 | 1,737 |

As you can see, beryllium has the highest melting point and boiling point of all the alkaline earth metals.