Question

the periodic table entry for beryllium (be) is shown below. beryllium has a single naturally occurring isotope. which isotopic notation correctly represents beryllium? o be_5^4 o be_0^4 o be_4^5 o be_4^9

Explanation:

Step1: Identify atomic number

The atomic number of beryllium from the periodic - table entry is 4. It is the sub - script in isotopic notation.

Step2: Identify mass number

The average atomic mass of beryllium is approximately 9.012. Since it has a single naturally occurring isotope, the mass number (the sum of protons and neutrons) is 9. It is the super - script in isotopic notation.

Step3: Write isotopic notation

The correct isotopic notation is $^{9}_{4}\text{Be}$, where the mass number 9 is on the top and the atomic number 4 is on the bottom.

Answer:

D. $^{9}_{4}\text{Be}$