6/11/2023 0 Comments Periodic table k 3d![]() You have already seen evidence of this in the fact that the ionization energies in period 3 are all less than those in period 2. Both of these factors offset the effect of the extra proton.Īs you go down a group in the Periodic Table ionization energies generally fall. The 3p electron in aluminum is slightly more distant from the nucleus than the 3s, and partially screened by the 3s 2 electrons as well as the inner electrons. The explanation for the drop between magnesium and aluminum is the same, except that everything is happening at the 3-level rather than the 2-level. That also reduces the pull from the nucleus and so lowers the ionization energy. The 2p orbital is screened not only by the 1s 2 electrons but, to some extent, by the 2s 2 electrons as well.The increased distance results in a reduced attraction and so a reduced ionization energy.2p orbitals have a slightly higher energy than the 2s orbital, and the electron is, on average, to be found further from the nucleus. Offsetting that is the fact that boron's outer electron is in a 2p orbital rather than a 2s. You might expect the boron value to be more than the beryllium value because of the extra proton. The outer electron is removed more easily from these atoms than the general trend in their period would suggest. The explanation lies with the structures of boron and aluminum. Why the drop between groups 2 and 3 (Be-B and Mg-Al)? Lithium's first ionization energy drops to 519 kJ mol -1 whereas hydrogen's is 1310 kJ mol -1. If you compare lithium with hydrogen (instead of with helium), the hydrogen's electron also feels a 1 pull from the nucleus, but the distance is much greater with lithium. One can think of the electron as feeling a net 1 pull from the center (3 protons offset by the two 1s 2 electrons). You might argue that that would be offset by the additional proton in the nucleus, but the electron does not feel the full pull of the nucleus - it is screened by the 1s 2 electrons. Its outer electron is in the second energy level, much more distant from the nucleus. The value of the ionization energy (2370 kJ mol -1) is much higher than hydrogen, because the nucleus now has 2 protons attracting the electrons instead of 1. It is close to the nucleus and unscreened. The electron is being removed from the same orbital as in hydrogen's case. There are no electrons screening it from the nucleus and so the ionization energy is high (1310 kJ mol -1). ![]() It is a very small atom, and the single electron is close to the nucleus and therefore strongly attracted. Hydrogen has an electronic structure of 1s 1. This offsets the attraction of the nucleus, so that paired electrons are removed rather more easily than you might expect.
0 Comments
Leave a Reply. |