a species of atoms having the same number of protons in their atomic nuclei
500
Iridium (Ir) is number 77 on the periodic table. How many valence electrons does it have?
2 valence electrons
500
How many electrons are there in the third shell of the atom with atomic number 23?
11
500
In the column headed by Oxygen, what is the charge of the ion formed when atoms of these elements give up electrons to get a more stable electron arrangement?