describe the change in the atomic radius of elements in:?

Question

a. period 2 (Li to Ne)
b. period 3 (Na to Ar)

Answer 1

a. quit preten=ding you REALLY know the PTE

b. talk nasty chem,istry and you are sOy BoMB

Answer 2

it is important to know WHY the change is just as Truckie said it is...


All the elements of a Period hold their Valence Electrons in the same Electron Shell (each row represents a new Electron Shell), meaning the same Distance from the positive nuclear charge. With COULOUMB LAW we have:

Force of attraction =[Q1xQ2 ]/square of Radius

Q1 & Q2 are the total magnitudes of the different charges (+ for each proton in the nucleus, - for each electron).

Radius is the distance from the nuclueus

1) Since an element always has the same # of protons Q1 is Fixed.
2) Since the electrons of elements in the SAME PERIOD occupy the same Electron Shell, the Radius is also Fixed

That leaves Q2 as a varying quantity (each element in a Period has its own # of electrons).

With this relationship, we can predict that as you move from left to right in the same period, the FORCE OF ATTRACTION between the Nucleus and the Valence shell will get stronger, because there is more Negative (-) charge (due to higher # of electrons present in the shell) to be "acted on" by the Positive (+) Nuclear charge.

This causes the atomic radii to DECREASE as you move from left to right in ANY period on the PTE.

Answer 3

Period 2: Decreasing radii from Li to Ne.
Period 3: Decreasing radii from Na to Ar.

Answer 4

radius increases as you go down a group and across the table.

know thy trends!