Explanation:
Group 2 elements in the periodic table are known as alkaline earth metals. These elements include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). These elements share similar chemical properties as they all belong to the same group.

Differences between the elements:
Although all the given options, except Beryllium, are Group 2 elements, Beryllium (Be) differs from the other elements in several aspects:

1. Electron configuration:
Beryllium has an electron configuration of 1s^2 2s^2, while the other Group 2 elements have electron configurations of ns^2 (where n represents the period number). This difference in electron configuration affects the reactivity and chemical behavior of Beryllium compared to the other elements in the group.

2. Atomic size:
Beryllium has the smallest atomic size among the Group 2 elements. As you move down the group, atomic size increases due to the addition of new energy levels. The larger atomic sizes of the other elements in the group result in different chemical and physical properties compared to Beryllium.

3. Reactivity:
Beryllium is the least reactive element among the Group 2 elements. It does not react with water or oxygen at room temperature, unlike the other elements. This is due to its small atomic size and high ionization energy, which make it less likely to lose electrons and form compounds.

4. Physical properties:
Beryllium has a higher melting point and boiling point compared to the other Group 2 elements. It also has a lower density and is harder and more brittle than the other elements. These differences in physical properties can be attributed to Beryllium's unique atomic structure.

In conclusion, Beryllium (Be) is the element that differs from the other Group 2 elements (Magnesium, Calcium, and Strontium) due to its electron configuration, smaller atomic size, lower reactivity, and distinct physical properties.