Do we need to memorize all the conversion units for SAT 2?
such as 1 inch = 2.54 cm and other stuff?
What is the reason for Peaks and Valleys in Ionization versus Atomic Number graph?
Yes. The conversions should be very commonplace by then. Know mostly your stoichio though…
Ionization energy is defined as the energy needed to discharge an electron from an atom in its gaseous state. The “peaks and valleys” are the graphical representation (usually obtained by infrared spectroscopy) of ionization energies. The higher a peak is, the more “work” or energy has to be put in to remove an electron, so something like Helium would have an extremely endothermic ionization energy. “Valleys” are just when very little work is put in to remove an electron. The reason why you see a valley right after a peak is because noble gases tend to have very high ionization energies due to their high effective nuclear charge and extremely small atomic radii, while alkali metals have relatively large atomic radii due to repulsion, making it a lot easier to remove the lone electron from the valence shell. Also, as you move left to right on these graphs, you’ll realize that the peaks get lower and lower. This is due to shielding. The more “shells” an atom has, the less attraction there is between the nucleus and the valence shell because the inner shells “shield” the nucleus. If you take two elements from the same family, say Helium and Argon, Argon has a smaller ionization energy despite both elements being noble gases. That is because Argon is in the third period, which means it has a lot more energy levels between the valence shell and he nucleus. Helium has the highest ionization energy of all elements because of its tiny atomic radius, single energy level, and strong attraction between the nucleus and the valence (its only) shell.