In which of the following are the atoms arranged by increasing atomic size?

[Smooth Operater]

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is it

Be < Na < Mg

or

Be < Mg < Na

 

[fireblast713]

Opps... my bad

 

[Flipper405]

Be < Na < Mg is the correct order.

I disagree... I say it's Be < Mg < Na. In a given row, the atomic radius (and therefore the size) will decrease as you go to the right because there are more protons and electrons attracting each other. This "compresses" the atom.

 

[fireblast713]

I disagree... I say it's Be < Mg < Na. In a given row, the atomic radius (and therefore the size) will decrease as you go to the right because there are more protons and electrons attracting each other. This "compresses" the atom.

Yea you're right I mixed up my trend. A.R. increases down a group and decreases across a period.

 

[schoi401]

A harder question would be ... predicting the ion's radius.
I always forget this trend. Somebody help me if you know the answer.

K+ < Ar < Cl- <S2-

Next... the reasoning behind this is that they all have the same number of electrons but different number of protons. Because sulfur has the least number of protons attracting the same number of electrons, its outermost valence electrons feel less pulling force and thus orbit in a larger circle than the rest.

 

[prettysmile]

Be < Mg < Na

 

[joonkimdds]

A harder question would be ... predicting the ion's radius.
I always forget this trend. Somebody help me if you know the answer.

K+ < Ar < Cl- <S2-

Next... the reasoning behind this is that they all have the same number of electrons but different number of protons. Because sulfur has the least number of protons attracting the same number of electrons, its outermost valence electrons feel less pulling force and thus orbit in a larger circle than the rest.

I think u wrote the right answer, so why are u asking?

 

[schoi401]

I think u wrote the right answer, so why are u asking?

I only meant people to verify my reasoning behind it. I saw the question and the answer from somewhere long time ago and I believe I didnt quite agree with their explanations. So I made up my own reasoning. Sorry if I offended you by answering my own question. 😀