![]() ![]() Across a period from left to right the electronegativity of atoms. Trends in reactivity in the periodic table Resource RSC Education This could be used to follow up some work on the periodic table where the trends in reactivity in groups 1 and 7 have been identified. Trends like this one demonstrate that electrons within atoms are organized in groups. 1 2 3 4 5 6 7 8 Electronegativity Electronegativity is a measure of an atom’s attraction for the electrons in a bond. Thus, it takes much more energy than just overcoming a larger ionic charge would suggest. ![]() However one can determine the valency of an element simply from its position in the periodic table. As you already know, the valency of an atom is the number of electrons it has in its outermost shell or the number of atoms in requires to complete its outermost shell. Why is it so much larger? Because the first two electrons are removed from the 3 s subshell, but the third electron has to be removed from the n = 2 shell (specifically, the 2 p subshell, which is lower in energy than the n = 3 shell). One of the trends in the modern periodic table is that of the valency of an atom. As you move down a group in the periodic table, atomic number increases - surely this means that nuclear charge increases as well But as you go down a group. The third IE, however, is over five times the previous one. The second IE is twice the first, which is not a surprise: the first IE involves removing an electron from a neutral atom, while the second one involves removing an electron from a positive ion. ![]()
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