For each of the following pairs, which element has the larger first ionization energy? Please provide a detailed explanation.
a. Rb, Mo
b. N, P
c. Ga, Cl
d. Pb, Rn
SOLUTION This solution is FREE courtesy of BrainMass!
Ionization energy is the energy required to pull an electron away from an atom's orbit, such that the atom is now an ion. The first ionization energy refers to the distinct amount of energy specific to each element required to pull the very first electron out of valence orbit. How tightly an atom holds on to valence electrons will depend mainly on two factors: the number of protons the atom has and the overall size of the elemental atom, which practically translates into how far away the valence orbit electrons are from the nucleus.
The farther these electrons are, the less held together they are by the nucleus, the easier it is to pull off, the less energy is required to ionize the atom, thus the smaller the ionization energy. The more protons there are; however, the more the atom holds onto the valence electrons, the more energy is required for the electron to break orbit.
Therefore, in general, trends in ionization energy follow this pattern in the periodic table:
Across a row in the periodic table, the number of energy levels remain the same, but the number of protons continue to increase, therefore, elements in the same row will, from left to right, have increasing # of protons for the same # of energy levels, thus the atoms will increasingly hold on to their electrons, increasing ionization energy.
When considering the columns, the elements farther down a column have more electrons and thus more energy levels. Each added energy level is farther from the nucleus, and since first ionization energy has to do with the first electron pulled off of the valence energy level, the farther the valence level is from the nucleus, the easier it is to eject an electron. Thus, ionization energy decreases down a column (or increases going up a column).
Looking at our examples:
Rb vs. Mo: Both row 5, Mo is farther to the right. This means Mo has more protons for the same number of energy levels as Rb.
N vs. P: Same column, but P directly below N. This means P has one more energy level than N.
Ga vs. Cl: Ga is both below Cl vertically, and to the left of Cl horizontally. It has one more energy level and a smaller proton:electron ratio than Cl. In this case, it's useful to consider the general trends as illustrated in the diagram provided to figure out the answer.
Pb vs. Rn: same row, Pb to the left of Rn, which means Pb has less protons than Rn, but both have the same # energy levels.
This should pave the way for you to figure out which has the higher first ionization energies. Hope it helps!© BrainMass Inc. brainmass.com September 27, 2022, 4:02 pm ad1c9bdddf>