an atom consists of 10 neutrons ,10 electrons,and 9 protons. The atom has gained an electron resulting in a charge of -1.
What is its mass number?
To determine the mass number of an atom, you need to add up the number of protons and neutrons in the nucleus.
Given that the atom has 10 neutrons and 9 protons, you can calculate the sum:
Mass number = number of protons + number of neutrons = 9 protons + 10 neutrons = 19
Therefore, the mass number of the atom is 19.