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cations and anions

Posted: Tue Oct 22, 2019 9:15 pm
by halle young 4A
Can someone please explain more in depth what cations and anions are and how they relate to the ionic radius? I know we touched on this in lecture but I still seem to be a bit confused

thanks

Re: cations and anions

Posted: Tue Oct 22, 2019 9:21 pm
by Hiba Alnajjar_2C
An atom is considered to be a cation when it's lost an electron(s) from its neutral state and is thus positive (a common method used to remember this is that "cats" are paws-itive). On the other hand, if an atom gains an electron(s), it becomes more negative and is considered to be an anion. Because cations have less electrons than the neutral atom, there is subsequently less electron/electron repulsion. As a result, the ionic radius is smaller. However, with anions, the ionic radius is bigger than that of the neutral atom since the presence of more electrons would lead to greater electron/electron repulsion that would result in a bigger ion. Essentially, when looking at ionic radii, cations<atoms<anions, because the presence/absence of electrons affects the size of the atom (particularly due to electron/electron repulsion). Hope this helps!

Re: cations and anions

Posted: Tue Oct 22, 2019 9:21 pm
by anjali41
An anion is a negatively charged ion. On the other hand, a cation is a positively charged ion. I think when you have a neutral atom and it either loses or gains an atom (which creates a cation or anion), the radius either decreases or increases respectively.

Re: cations and anions

Posted: Tue Oct 22, 2019 9:59 pm
by MMckinney_4H
Atoms' numbers of protons and electrons are balanced to have a charge of 0. However, when electrons are exchanged, some atoms can either have a positive or have a negative charge depending on which atom receives an electron and which one gains one. When an electron which has a negative charge is gained, the atom has a negative charge. These are called anions. The opposite is true for positive ions (cations) who lose the electron and therefore have more protons than electrons.

Re: cations and anions

Posted: Tue Oct 22, 2019 10:08 pm
by Nyari Muchaka_Discussion 4A
When ionic bonds are made a highly electronegative atom is bonding with an atom of less electronegativity. This essentially means one atom wants electrons more than the other atoms in order to fill its valence shell and become more stable. Thus, this atom will steal electrons from the atom it bonds to, making it more negative. Say you have fluorine with seven electrons in its valence shell and needs one more to stabilize it. It becomes highly electronegative and if it comes across and element like hydrogen, it will steal hydrogen's electron in order to fill its valence shell. Now fluorine has a charge imbalance as it has more electrons than protons, and thus becomes an anion as it is now negatively charged. Hydrogen would become a cation as it loses an electron so it has more protons than electrons. The two will remain bonded however as their opposite charges will attract each other. Their radius will be different than say the radius of a covalently bonded molecule due to the nature of the bond. The opposite charges and stealing of an electron may draw the two atoms closer together than just a covalently bonded molecule and thus the radius will be smaller.

Re: cations and anions

Posted: Tue Oct 22, 2019 10:36 pm
by serenabirkhoff_1K
Hiba Alnajjar_4B wrote:An atom is considered to be a cation when it's lost an electron(s) from its neutral state and is thus positive (a common method used to remember this is that "cats" are paws-itive). On the other hand, if an atom gains an electron(s), it becomes more negative and is considered to be an anion. Because cations have less electrons than the neutral atom, there is subsequently less electron/electron repulsion. As a result, the ionic radius is smaller. However, with anions, the ionic radius is bigger than that of the neutral atom since the presence of more electrons would lead to greater electron/electron repulsion that would result in a bigger ion. Essentially, when looking at ionic radii, cations<atoms<anions, because the presence/absence of electrons affects the size of the atom (particularly due to electron/electron repulsion). Hope this helps!

Thank you so much this helped a lot!!!!!