CHEMISTRY COMMUNITY

Can someone summarize the periodic trends for the following: atomic radius, ionic radius, ionization energy, electron affinity?

Thanks in advance :)

based on the lectures:
atomic/ionic radii: increases down (more shells=e- farther from nucleus), decreases across (more nuclear charge pulls e- closer)
ionic radii: cations smaller than parent/anion larger than parent
ionization energy: decreases down (bigger size=farther e-=less energy req.), increases across (due to stronger nuclear charge holding e-)
e- affinity: generally, increases across, decreases down (but less of a periodic trend/more based on the equation, i think)

Atomic/Ionic radius:
Trend: Increases down a group and increases as you go left across a period (or you could remember it as decreases as it goes right). Increases as you approach bottom left corner
Reason: bigger atoms have larger radii and larger atoms in the same period have more nuclear charge so the electrons are pulled in more
Reason (ions): same reason, the more protons an ion has, the smaller the radius within a given period

Ionization Energy:
Trend: Increases up a group and increases across a period as you go right (Increases as you approach top right corner)
Reason: smaller atoms are harder to ionize since the electrons are so close to the nucleus and less valence electrons are easier to give up. Basically the inverse of the atomic radius trend

Electron affinity:
Same as ionization energy; increases up a group and increases across a period as it goes right (Increases as you approach top right corner).
Reason: I'm honestly not sure. Sorry :(

Do remember that these trends are just guidelines and that atoms are weird and there are almost always exceptions to these trends.

Atomic Radius
Period - atomic radius decreases as you go from left to right across a period because stronger attractive forces in atoms (as you go from left to right)
with the electrons cause the atom to be kept together a little tighter.

Group - atomic radius increases as you go down a group since there is an increase in the size of the nucleus (protons + neutrons) each time you move from period to period down a group + new energy levels are added to the atom as you move from period to period down a group, making the atom bigger.

Ionization Energy
Period - ionization energy increases as you go from left to right across a period since elements on the right of the chart want to take others atom's electrons, instead of giving them up, because they are close to getting the octet. Elements on the left of the chart tend to give up their electrons so it is easy to remove them, so lower ionization energy.

Group - ionization energy decreases as you go down a group because the shielding effect makes it easier to remove the outermost electrons from those atoms that have many electrons.

Electronegativity

Period- electronegativity increases as you go from left to right across a period. Elements on the left of the period table have few valence electrons and would rather give away those electrons than grab another atom's electrons so they have low electronegativity. Elements on the right side of the period table only need a few electrons to complete the octet, so they want to to grab another atom's electrons.

Group - electronegativity decreases as you go down a group because elements near the top of the period table have few electrons to begin with so they have a stronger desire to get more electrons. Elements near the bottom of the chart have a lot of electrons so losing or getting an electron is not as big of a deal. This is from the shielding effect where electrons in lower energy levels shield the positive charge of the nucleus from outer electrons resulting in those outer electrons not being as tightly bound to the atom.

Is there a basic rule for whether being in a period or being in a group will change the ionization energy/atomic radius/electronegativity? In short, does going down or across make a bigger difference?

I personally write a bunch of arrows on my periodic table

This is how my periodic table usually looks :)

https://www.google.com/url?sa=i&url=https%3A%2F%2Fblog.prepscholar.com%2Felectronegativity-chart-trend-definition&psig=AOvVaw2MzPa7PM0MsY8Ma01YKgOD&ust=1634054453450000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCKC1jLDdwvMCFQAAAAAdAAAAABAD

Idk if this url will work but I’m just adding this electronegativity chart b/c the other chart doesnt have it

Hello!

I've found this table most useful in summarizing periodic table trends:

https://www.thoughtco.com/chart-of-peri ... nds-608792