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# Elements in the Periodic Table Question watch

1. does anyone know the answer is 1,2 and 5

and not 1,2 and 4
2. From the electron configuration we know that the element has 19 electrons therefore it is Potassium (K)
Metals reacts with oxygen to form a metal oxide therefore 5 is correct. 4K + O2 = 2K2O
The element above Potassium is Sodium. Potassium is more reactive than sodium because there is greater shielding as there is one greater oribital than sodium. Therefore 4 is incorrect.
3. (Original post by medhelp)

does anyone know the answer is 1,2 and 5

and not 1,2 and 4
The reactivity of alkali metals, such as potassium in this case, is dependent on its ability to lose an electron. As you go down group 1, the atomic radius gets bigger, there is more electron shielding and hence there is a smaller force between the valence (outermost) electron and the nucleus - hence the valence electron is lost more easily. Therefore 4 is incorrect because reactivity increases as you go down group 1.
4. (Original post by Jpw1097)
The reactivity of alkali metals, such as potassium in this case, is dependent on its ability to lose an electron. As you go down group 1, the atomic radius gets bigger, there is more electron shielding and hence there is a smaller force between the valence (outermost) electron and the nucleus - hence the valence electron is lost more easily. Therefore 4 is incorrect because reactivity decreases as you go down group 1.
but if reactivity decreases down the group, the element above X will be more reactive than X... ?
If an electron is more easy to lose that = more reactive ?

(Original post by LelouchViBrit)
From the electron configuration we know that the element has 19 electrons therefore it is Potassium (K)
Metals reacts with oxygen to form a metal oxide therefore 5 is correct. 4K + O2 = 2K2O
The element above Potassium is Sodium. Potassium is more reactive than sodium because there is greater shielding as there is one greater oribital than sodium. Therefore 4 is incorrect.
you're not allowed a periodic table for this question :/ I guess I could've figured out it's a metal because 1 electron in its outer shell = group 1
so reactivity increases as you go down group 1?

Also I can only find the reactivity series in a really simple form: K Na Li Ca Mg Al (decreasing) so you can you please check this:

(more reactive to least reactive)

Fr
Cs
Rb
K
Na
Li
Ra
Ba
Sr
Ca
Mg
Be
Al

carbon

Zn
Fe

hydrogen

Tin (can't remember symbol)
Pb
Cu
Ag
Au
Platinum (can't remember symbol)
5. (Original post by medhelp)
but if reactivity decreases down the group, the element above X will be more reactive than X... ?
If an electron is more easy to lose that = more reactive ?

you're not allowed a periodic table for this question :/ I guess I could've figured out it's a metal because 1 electron in its outer shell = group 1
so reactivity increases as you go down group 1?

Also I can only find the reactivity series in a really simple form: K Na Li Ca Mg Al (decreasing) so you can you please check this:

(more reactive to least reactive)

Fr
Cs
Rb
K
Na
Li
Ra
Ba
Sr
Ca
Mg
Be
Al

carbon

Zn
Fe

hydrogen

Tin (can't remember symbol)
Pb
Cu
Ag
Au
Platinum (can't remember symbol)
I meant to say reactivity INCREASES as you go down group 1

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