Chemical families?

with the exception of the transition elements,groups 3-12 in the periodic table,and the noble gases,group 18, atomic radii_________within periods,while atomic radii_________within groups








A.increase,decrese


B.decrease,increase


C.increase,remain roughly constant


D.decrease,remain roughly constant

Chemical families?
the answer is B


the atomic radii decrease down the period as the nuclear charge increases.This is due to the adding of elctrons to the valence shell and protons to the nucleus.


atomic radii increase down the group as the screening effect increases.





OR from left to right of a period, the number of protons in nucleus increases,hence increases the power of nucleus holding on to the electrons .Hence the atomic radii decreases.


when going down a group,the number of shells increases.The distance between valence shell and nucleus is wider hence it is harder for nucleus to hold tight to the valence shell down a group
Reply:cool. i had to know this last chapter. I'm pretty sure its B. The the atoms get smaller moving from left to right across each period, and get larger going down a group.