Atomic radius question!!! HELP ME

[Banana_nut95]

HELP, This was a question from the DAT Destroyer Gen. Chem. pg.115

Question: Rank by size :
Al, K, Br, I

Answer: K > Al > I > Br

I thought the more electrons it has, the bigger the atom
Al = 13e
K = 19e
Br = 35 e
I = 53e

So according to my logic, shouldn't the answer be I > Br > K > Al

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[DAT Destroyer]

HELP, This was a question from the DAT Destroyer Gen. Chem. pg.115

Question: Rank by size :
Al, K, Br, I

Answer: K > Al > I > Br

I thought the more electrons it has, the bigger the atom
Al = 13e
K = 19e
Br = 35 e
I = 53e

So according to my logic, shouldn't the answer be I > Br > K > Al

As you go across the table size will generally DECREASE.....and as you go down a group size will INCREASE. Consult any Gen Chem text for more clarity.

 

[NextStepTutor_2]

Hello,

Here is the reasoning behind the periodic table trends for the atomic radius:

1. Radius increases as you go further down the periodic table. This is because in atoms further down the periodic table, you are adding electron shells. In other words, there are electrons occupying electron shells that are further from the nucleus.

2. Radius decreases as you go from left to right on the periodic table. This is because there are more protons in the nucleus as you go across the period. More protons means a STRONGER PULL on the electrons in the outer shell and a smaller overall radius.


Hope this helps!


Alicia

 

[Banana_nut95]

thanks so much!!