Which has the lowest first ionization energy?

The answer is A:It is Ba because out of the 5 choices, it is the furthest tothe left and bottom. By being to the left of the periodic table, ithas a lower nuclearcharge, which creates a weaker attractionbetween its valence electrons and its nucleus. By being near thebottom, it has more energy levels, which meanthe valence electronsare further away from the nucleus and creating weak attraction.Also there is electron shielding within its orbital since it isapaired electron and shielding from the core electrons, making theattraction from the nuclear extremely weak. Thereby the valenceelectron is moreeasily removed compare to your other choices andthus it has the lowest first ionization energy.Wow...the first guy got a lucky guess and the other's anidiot.

The answer is BaCl cannotgive out electrons easily. So it has very high 1st IEPalso shows very high first IE for the same reason.Silicon prefers to take 4 electronsand so shows high IEBoth Ba and Ca show low 1st and 2nd IE values as theyboth have to lose 2 electrons to obtain octet configuration.But Ba being in the 6th period shows lesserfirst IE value.This is due to large size and decreased force ofattraction of the nucleus on theoutermost electron.

Ba ,has largest size and least electro negetivityamong the given atoms so that it may have lowest ionisation energy .

The first ionisation potential of the above elements in voltsare given as follows .a ) Ba (Z = 56 ) = 5.212 Vb) Ca ( Z = 20 ) = 6.113 Vc) Si ( Z = 14 ) = 8.151 Vd) P ( Z = 15 ) = 10.486 Ve) Cl ( Z = 17 ) = 12.967 VOut of the above , Ba is having lowest ionisationpotential . B'Coz it is larger in size . So providing little amountof energy , electron can beremoved .