Cations and Anions

[Samantha Loc 1B]

When considering the effects of losing/gaining electrons, why is it that cations are smaller than their parent ions while anions are larger?

Also, if a cation of one element and anion of another element are isoelectronic, how do you know which will have a larger radii?

[Jocelyn Chin 1K]

I think that cations will be smaller because when you remove an electron, the proton to electron ratio increases, so protons can better attract electrons to the nucleus. Also, I think anions will be larger because more electrons will be in electron orbitals, so there is more electron electron repulsion, which increases atomic radius.
For the second question, you know which has a larger radii based on the number of protons. The more protons, the smaller the ion will be, because there are more protons attracting electrons to the nucleus, so electrons are closer to the nucleus, which decreases atomic radius.

[Noa Popko 3I]

Cations are positively charged and have lost electrons, and since there are fewer electrons but the same amount of positively charged protons in the nucleus, the electrons are pulled more tightly in creating a smaller radius. On the other hand, anions are negatively charged and have gained electrons, and because there are more electrons but the same amount of positively charged protons in the nucleus, the electrons are not held as closely creating a larger radius.

Among isoelectronic elements, look at the number of protons. More protons means a stronger positive force pulling the electrons in and making the radius smaller.

[Alyssa H]

I try to think of it like a game of tug-of-war! If electrons and protons are two teams, whenever one electron is added or subtracted, one "team" becomes stronger. When a cation is formed, an electron leaves its "team," so the protons can pull the electrons closer and make the atom smaller, and vice versa when an anion is formed. Hopefully this makes sense :D

[105719095]

Cations are smaller because they are positively charged ions, meaning they have less electrons. Electrons make up an atom's radius, so if the atom has less electrons, then the radius is smaller. Anion are larger because they are negatively charged ions, meaning they have more electrons. The radius will be larger with more electrons. In isoelectronic elements, the element with the more protons will have the smaller radii because the protons pull the electrons in closer.

[Skylar Lo 2C]

Cations would be smaller because they have lost an electron meaning the protons have a larger magnetic force on the electrons. Anions would be larger because with an electron there would be more electron-electron repulsion, thus expanding the electron cloud.

[Stephen_Kim_1D]

Cations lose electrons but their number of protons remains the same (higher than the number of electrons). This means the protons attract these fewer electrons more tightly. Anions are the opposite. They gain electrons but their number of protons is now lower than the number of electrons. The protons now have "more electrons" to attract and don't pull them as tightly as in their parent atoms.

For your second question, the greater the protons, the stronger the attractive force = tighter/smaller radius.

[Emily Quill 2H]

Hi! For the second question, the more protons one atom has the smaller the atomic radius will be, so you can compare using the number of protons.

[indigoaustin 3H]

Cations are smaller than parent ions because removing an electron increases attraction to the nucleus. Conversely, anions are larger than parent ions because gaining electrons lowers effective nuclear charge.

If ions are isoelectronic, you can determine size based on the atomic number/number of protons. More protons indicates greater attraction towards the nucleus and smaller size.

[Sidharth Paparaju 3B]

Cations are smaller since an electron is gone, so their is less electron shielding, which means that Zeff is higher. Anions get more electrons, increasing shielding and decreasing Zeff.

[Erin Woolmore 1C]

Hi! Cations have a bigger radius because they have lost electrons, so the more positively charged nucleus does not attract the remaining electrons in the valence shell as tightly. Anions have a smaller radius because they have gained electrons, so their electrons are more tightly drawn to its nucleus. As for the second part of your question, for isoelectronic elements, the atom with more protons will have a more positive nucleus, therefore having a stronger pull on the electrons, making its atomic radius smaller.