Question

3 of 14
actinide series**
89 ac (227)
90 th 232
91 pa 231
92 u 238
93 np (237)
94 pu (244)
95 am (243)
96 cm (247)
97 bk (247)
98 cf (251)
99 es (252)
100 fm (257)
101 md (258)
102 no (259)
103 lr (262)
which of the diagrams is the correct model for the element beryllium?
a
b
c
d

Explanation:

1. First, find beryllium's atomic number: it is 4. This means it has 4 protons ($p^+$) and, in a neutral atom, 4 electrons ($e^-$).
2. Beryllium's most common isotope has 5 neutrons ($n$), so the nucleus has $4p^+ + 5n$.
3. Use the electron shell rule: the first shell holds max 2 electrons, the remaining 2 electrons go to the second shell.
4. Match this to the options: Option B has 4 protons, 5 neutrons, 2 electrons in the first shell, and 2 in the second shell.

Answer:

B. <Diagram with 4 protons, 5 neutrons, 2 inner-shell electrons, 2 outer-shell electrons>