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Is it necessary to know or memorize the electronegativity chart in the book? It is figure 3.12 in the book. Will we be asked questions that require these specific values? or should we just know the trend?
In general, I wouldn't memorize these kinds of values. The best way of thinking about electronegativity is that it is closely related with ionization energy and electron affinity (in fact, it's derived from these two values). Just consider how the trends work. Electron affinity and Ionization energy both increase across a period/row, and decrease down a column/family. Electronegativity will generally follow this trend. A rule of thumb is that F is the most electronegative element: those near it also have a relatively high electronegativity.
another way that I remember it is that electronegative elements like in group 17 really want to have additional electrons to reach the noble gas configuration (reach the noble gas state). this is the opposite of group 1 because they form cations and want to lose electrons to reach the noble gas configuration
The definition of electronegativity itself is "the electron-pulling power of an atom." The best way to think of it conceptually without having to memorize any numbers is to think of it in terms of electron affinity. The trend for electron affinity increases as you go from left to right across a period from the periodic table - of course, which the exceptions of particular elements that we have learned. Similarly, electron affinity decreases as you go down a group. Therefore, you can think of the trends of electronegativity as corresponding with the trends of electron affinity.
Memorization of the electronegativity chart is not the most useful way to know the electronegativities. I would recommend remembering the basic trends and possible exception by knowing the number of valence electrons of each atom at ground state due to their electron configurations.
It is definitely not necessary to memorize these numbers. It is more important to know the trends of electronegativity. A trick I use for memorizing trends is to know the element with the highest electronegativity and a line pointing in that direction is the general trend.
The general trend that you need to remember is that electronegativity increases as you go up the periodic table and to the right! I believe this should be enough in order to figure out which elements are more electronegative than others.
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