The general trend when going left to right across a period is that the electronegativity increases. The electronegativity of an element is a measure of how likely, when in a bond with another atom, that atom will "pull" the bonding electrons toward itself. Going down a group, there are more inner electrons to "screen" the effects of the nucleus, so the ionization energy decreases What this basically is, is that the inner electrons act as a "screen" or "shield" that "block" the attraction to the nucleus, and thus the electrons are farther from the nucleus, and are easier to ionize because less energy is required. This is due to a property called electron screening. Going down a group, the ionization energy generally decreases. If they "would rather gain an electron than lose one", the energy required to take away an electron would thus be higher.įor metals, whose valence electrons aren't filled very much, they require much less energy to lose an electron (hey "prefer" to lose electrons to become cations) so therefore ionization energy generally increases from left to right. You may recall that nonmetals (those on the right side with more filled valence shells) tend to gain electrons to fill its valence shell. Going left to right, the number of valence electrons increases by one, and the valence shell thus becomes more and more filled. Going left to right across a period, the general trend is that ionization energy increases. The ionization energy of an element is the amount of energy required to remove the most loosely-bound electron from an isolated ("gaseous") neutral atom. Here is a visual periodic table representing this: The size of the atom thus increases as you go down a group. This means that the outer electrons occupy a different shell that is farther from the nucleus (the period number increases as you go down a group). Why?Įach successive element you come across is in a new period. Going from top to bottom within a group on the periodic table, the general trend is that the radius increases. The pull the protons exert on the electrons is greater in magnitude than the pull the electrons exert on the protons, so the overall change is that the electrons are pulled in closer, and thus the "size" of the atom has decreased. Recall that the positively-charged protons attract the electrons toward the nucleus. Why is this so?įor each successive element you come across, the atomic number, and thus the number of protons and electrons, increases by #1#. Going left to right across a period on the periodic table, the general trend is that the radius decreases with each successive element. There are several types of atomic radii, but we need not preoccupy ourselves with that, as they generally all follow the same trends. The atomic radius of an element is, for general purposes, the distance from the center of the atom's nucleus to the outermost space occupied by electrons in the "electron cloud". The four primary periodic trends I can think of are trends in
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