Question

protons: neutrons: electrons: what is the mass number? 0

Explanation:

Step1: Identify number of protons and neutrons

From the image, there is 1 proton and 1 neutron.

Step2: Recall mass - number formula

Mass number = number of protons+number of neutrons.

Step3: Calculate mass number

Mass number = 1 + 1=2.

Answer:

2