Question

atomic number relating to activation energy

Answer 1

which element has the highest Ea?
cesium
lithium
potassium
sodium



so what i know so far is as the atomic number increases it gets more and more reactive therefore the faster they react...
so in that case i think it is litium since is is the least reactive.....?

@Hoslos

Answer 2

Activation energy is the amount of energy required to remove an electron from the outermost shell of an element in its gaseous form.
Down the group, the number of shells increase, the atomic size as well and so the attraction of electrons to the nucleus decreases. Hence Ea increases, as the electrons become less attractive to the nucleus.

Across the period, the activation energy increases, because the atomic size decreases. As this happens, the electrons become more attractive to the nucleus.
The answer would be lithium, as it is the smallest atom.

Answer 3

Ok Hoslos is right, but don't get your terminology mixed up.

What he described is ionization energy, the energy needed to remove a valence shell electron.

Activation energy is the minimum energy needed to begin a chemical reaction.

Answer 4

Just remember:

Bigger the atomic radius (which is proportional to atomic number) the farther the valence electrons are from the pull of the protons in the nucleus, therefore less energy is needed to remove (ionize) them.

And vice versa for smaller atomic radii, where the outermost electrons, are very close to the protons in the nucleus do more energy would be needed to ionize them