Question

Which of the following elements has the smallest first ionization energy? How do you determine this?
A. Sodium
B. Calcium
C. Potassium
D. Magnesium

Answer 1

Hint: In the periodic table, the ionization energy of the element diminishes when the nuclear size of the elements increments. This is because of the protecting impact. As the nuclear size expands the power of fascination between the core and the valence electrons present in the furthest orbital reductions, on account of the presence of internal shells electrons.

Complete step by step answer:The proportion of the capacity of electrons (appealing powers) to be held in its place or proportion of the battle for eliminating the electrons from the iota is named as ionization energy.
Lithium is the main element present in group $$1$$. Its first ionization energy is $$520kJ/mol$$.
Sodium is the subsequent element present just beneath lithium. Its $$first$$ ionization energy is $$496kJ/mol$$.
Potassium is the $$third$$ element present beneath sodium.
Rubidium is the $$fourth$$ element present beneath sodium. Its $$first$$ ionization energy is$$403kJ/mol$$.
Cesium is the $$fifth$$ element present beneath the rubidium. Its $$first$$ ionization energy is$$376kJ/mol$$.
As potassium $$\left(K\right)$$ is available between the elements sodium and rubidium, its $$first$$ ionization energy will be between$$496kJ/mol$$ and $$403kJ/mol$$.
In this way, the primary ionization energy of potassium $$\left(K\right)$$ is$$419kJ/mol$$.
Ionization energy diminishes DOWN a Group, and increments from left to directly across a Period as we face the Periodic Table.
The order for $$first$$ ionization energies is along these lines (smallest to largest):
$$Potassium\to sodium\to calcium\to magnesium$$.
As a scientific expert, as an actual researcher, you ought to, nonetheless, consistently inspect the information. Here is a beginning.
That ionization energy should diminish down a Group, down a section of the Periodic Table, is sensible, on the grounds that the valence electron is farther taken out from the atomic center. Across the Period, across a column, from left to right the ionization energy should increment since we add atomic charge that is defectively protected by the valence electrons.
Along these lines, the right alternative is choice $$\left(C\right)$$.

Note:
As we drop down in the group the nuclear size increments because of the expansions in the quantity of shells. At the point when the ionization energy of an element is high, at that point the expulsion of the electron will turn out to be more troublesome.