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How do you determine reactivity of elements on the periodic table?I have to determine...

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How do you determine reactivity of elements on the periodic table?

I have to determine between three elements (K, Ba, Al) which has the highest and lowest reactivity.  Is there any way to remember which way is increasing/decreasing in periods and groups, like there is for atomic radii and electronegativity?

Thanks for any help! :)

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ncchemist's profile pic

Posted (Answer #1)

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We are determining the reactivity of potassium, barium, and aluminum.  These are all classified as metals.  The general periodic trend for metals is that reactivity increases going down and to the left.  Lone s-shell electrons in higher energy orbits are easier to remove from the metals.  For non-metals, the trend is the exact opposite.  But we are focusing on three metals K, Ba, and Al.  Potassium is the furthest to the left and aluminum is furthest to the right.  Barium is a little right of K but further down than both.  This all makes Al the least reactive, but K and Ba are more of a toss up.  I would think that being in group 1a would give K the edge.  So the reactivity ranking from highest to lowest would be K, Ba, Al.

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Posted (Answer #2)

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metals- reactivity increases as you go down the group

non metals- it decreases as you down the group

for all periods, the reactivity will decrease till the middle of the period(element with valency 4) and then increases again till the valency -1..

but if you know the valency of an element, like -1 or +3, then one with the lower number is more reactive.because it will easily lose or gain enough electrons. but sodium and potassium have same valency, however sodium is less reactive than potassium.

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