Question

Which out of Li, Na, K, Be, Mg, Ca has lowest ionization enthalpy and why?

Answer 1

Hint: The distance between an atom's nucleus and its outermost shell is measured in atomic size. The atomic radius is defined as the smallest distance between the nuclei of an atom and the atom's outermost shell in basic chemistry.

Complete answer: In basic words, ionisation energy is a measure of how difficult it is to remove an electron from an atom or ion, or how likely an atom or ion is to yield an electron. The loss of one electron generally occurs in the chemical species' ground state.
In more technical terms, ionisation energy is the lowest amount of energy that an electron in a gaseous atom or ion must receive to escape the nucleus' influence. It's also known as ionisation potential, and it's often an endothermic process.
An electron's ionisation energy rises with the atomic number of the atom and falls with higher energy orbitals. As we proceed from left to right throughout the periodic table, the ionisation energy increases because of the decreasing atomic radius.
The ionisation energy drops as we proceed from top to bottom. This is owing to the fact that as we progress down the group, the elements have more electron shells. Furthermore, the electrons are separated from the nucleus's attractive attractions by a wider distance.
Now from the given question,
Because of its bigger atomic size, K has the lowest ionisation energy among these elements. Because the force of attraction between the valence electron and the nucleus is weaker, it can readily lose one electron.
Hence, K has the lowest ionization enthalpy.

Note:
The atomic ionisation energy may also be calculated using Bohr's atom model. His model predicts that the electron will take numerous pathways around the nucleus, which contains protons and neutrons. Each route or orbit is separated from the nucleus by a set distance. Each orbit also represents a constant amount of energy. The energy of the orbit will be present in the electron because it is a particle. A particle can absorb energy and then leap to the next higher energy orbit. If more energy is available and absorbed, the electron will be drawn out of the nucleus's force of attraction, and hence out of the atom.