Question

how many protons does this have? * 19 9 f 9 19 10 -1 28

Explanation:

Step1: Identify atomic number meaning

The sub - script number in an atomic notation represents the atomic number. For the element $^{19}_{9}F$, the sub - script number is 9.

Step2: Recall proton - atomic number relationship

The atomic number of an element is equal to the number of protons in its nucleus.

Answer:

A. 9