Atomic number Tc = 43 , which is equivalent to the number of protons in nucleus.
Number neutrons = mass number - number of protons = 99 - 43 = 56 neutrons .
Number of electrons = number of protons - charge = 43 - (+7) = 36 electrons
Explanation;
-Atomic number is the number of proton in the nucleus of an atom of a given element. Mass number is the total number of protons and neutrons in the nucleus of an atom. A neutral atom has equal number of protons and neutrons.
-Isotopes are atoms of the same element with the same atomic number but different mass number.
you are using your shoulder muscle. The reason you are using this muscle is when you put your arm strait up there is no reason to use a bicep or tricep muscle.