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As the atoms go down a group, there are more electron levels added and the valence electrons (the outer shell of electrons) gets farther away from the nucleus, which not only increases the radius because there are more electron levels in between, but the attraction that binds the electrons and nucleus together lessens, which creates a greater atomic radius
As you go down a group, the radius increases because the principal quantum number (n) increases, but you have you take more into account. The nuclear charge increases because there are more protons pulling electrons, but the effective nuclear charge is affected because the electron-electron repulsions push the radius further out as well as the electron shielding from the inner levels and subshells causing the attraction of the valence electrons to the positively charged nucleus to be weaker. Thus, the ionic radius increases as you go down a group.
I know ionic and atomic radius follow the same trend in the periodic table increasing down the group and decreasing across a period, but does the covalent radius also follow this trend? Lavelle mentioned it in class but I was confused about the trend it follows.
Ruby Richter 4G wrote:I know ionic and atomic radius follow the same trend in the periodic table increasing down the group and decreasing across a period, but does the covalent radius also follow this trend? Lavelle mentioned it in class but I was confused about the trend it follows.
I believe covalent radii follow the same trends because as you move down a group, additional shells are still being added which would increase the radii. Conversely, as you move across the period, electrons are being added in the same shell, decreasing the radii regardless of the type of bond.
But someone please correct me if I'm wrong! This is just based on what I understood from today's lecture.
Kimberly Bauer 4E wrote:I have a question regarding whether it's a cation or anion. Does that affect the ionic radius of the element? In my notes, I wrote "cations are smaller than their parent atoms and anions are larger"
I wrote the same, I think they do have an effect on the radius of an element, but I don't understand how we could find those numbers? They are given right?
The actual values of the atomic radius are always given. You just need to know that cations are smaller than their parent atoms because they have less electrons which means there is less electron repulsion. Anions are larger than their parent atoms because they have more electrons and thus more electron repulsion.
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