Which of the following best describes an electron?
a It has no charge and about the same mass as a proton.
b It has a negative charge and much less mass than a proton.
c It has a positive charge and much more mass than a neutron.
d It has a negative charge and about the same mass as a neutron
Which of the following is the mass number of an element?
a Number of protons + Number of neutrons in each atom
b Number of protons + Number of electrons in each atom
c Number of neutrons + Number of electrons in each atom
d Number of protons + Number of neutrons + Number of electrons in each atom