Question

multiple choice 5 points
what element has 9 e - and an atomic mass number of 19?
f
ag
kr
pd

Explanation:

In a neutral atom, the number of electrons (\(e^-\)) equals the number of protons. The number of protons is the atomic number (\(Z\)). So, if there are \(9e^-\), the atomic number \(Z = 9\).
The atomic mass number (\(A\)) is given as \(19\).
Looking at the periodic table:

• For \(F\) (Fluorine): \(Z=9\) and \(A = 19\) (common isotope).
• For \(Ag\) (Silver): \(Z = 47\).
• For \(Kr\) (Krypton): \(Z=36\).
• For \(Pd\) (Palladium): \(Z = 46\).

Answer:

F