Calculate the number of protons, neutrons, electrons for the chemical element selenium and ruthenium.

Let’s use the periodic table. The number of protons and electrons is equal to the ordinal number of the element. To find the number of neutrons, you need to subtract its ordinal number from the atomic mass of an element
Selenium. Atomic mass = 79, ordinal = 34
Number of protons = 34
Number of electrons = 34
Number of neutrons = 79 – 34 = 45
Ruthenium. Atomic mass = 101, ordinal = 44
Number of protons = 44
Number of electrons = 44
Number of neutrons = 101 – 44 = 57