These are two questions and two answers.
Question 1: protons, electrons, and neutrons in I⁻
Answer: 53 protons, 54 electrons, and a variable number of neutrons. One possibility is 74 neutrons, if it is the most stable isotope, iodine-127.
Explanation:
1) I⁻ is the anion of the atom I
2) One negative charge means that one electron has been added to the neutral atom of I.
3) The element I has atomic number 53 (you see this is a periodic table).
4) The atomic number 53 means that it has 53 protons.
5) The neutral atom has the same number of electrons than protons, i.e. 53. Since the anion I⁻ has one additional electron, it has 54 electrons.
6) The number of neutrons is not a fixed quantity. Different isotopes of the same element have different number of neutrons.
7) The isotope iodine-127, which is the only stable isotope of iodine has 74 neutrons.
The number of neutrons is calculated as the mass number (127) less the number of protons (53): 127 - 53 = 74.
Question 2: protons, electrons, and neutrons in Li⁺
Answer: 3 protons, 2 electrons, variable number of neutrons, may be 3 or 4 depending of the isotope.
Explanation:
1) Li⁺ is the cation of the atom Li
2) One positive charge means that one electron has been removed from the neutral atom of Li.
3) The element Li has atomic number 3 (you see this is a periodic table).
4) The atomic number 3 means that it has 3 protons.
5) The neutral atom has the same number of electrons than protons, i.e. 3. Since the anion Li has one less electron, it has 2 electrons.
6) The number of neutrons is not a fixed quantity. Different isotopes of the same element have different number of neutrons.
7) There are two natural stable isotopes of lithium.
The isotope lithium-7, has 4 neutrons, and the isotope lithium-6 has 3 neutrons.
The number of neutrons is calculated as the mass number less the number of protons (3):
i) 7 - 3 = 4
ii) 6 - 3 = 3
