Question

the atomic number is the number of protons in the nucleus.which element has an atomic number of 19?

Explanation:

The atomic number is the number of protons in the nucleus of an atom. Looking at the periodic table information provided, potassium (K) has an atomic number of 19. Sodium (Na) has an atomic number of 11 and calcium (Ca) has an atomic number of 20.

Answer:

Potassium