Final answer:
A beryllium atom is represented by a nucleus with four protons, surrounded by two electrons in the 1s orbital, and two valence electrons in the 2s orbital, depicted in an electron dot diagram similar to helium. Beryllium hydride, BeH₂, has a linear structure due to the two electron groups surrounding beryllium.
Step-by-step explanation:
Correct Representation of a Beryllium Atom
An atom of the alkaline earth metal beryllium, with an atomic number of 4, contains four protons in the nucleus and four electrons surrounding the nucleus. The electrons occupy energy levels with the configuration 1s² 2s². The fourth electron fills the remaining space in the 2s orbital. Therefore, the correct representation of a beryllium atom includes a nucleus with four protons (and typically five neutrons for the most common isotope, 9Be), surrounded by two electron shells: the first shell containing two electrons in the 1s orbital, and the second shell also containing two electrons in the 2s orbital. Since beryllium has two valence electrons in its 2s shell, its electron dot diagram is similar to that of helium, symbolized as Be with two dots representing the two valence electrons.
When discussing compounds such as Beryllium hydride (BeH₂), the bonding scenario is more complex because beryllium's filled 2s orbital must interact with the 1s orbitals of hydrogen. Beryllium hydride adopts a linear structure as per the Valence Shell Electron Pair Repulsion (VSEPR) model because there are only two electron groups around beryllium which orients them as far apart as possible.