ionization energies Flashcards
explain ionization energy
electrons can be removed from atoms and the energy it takes to remove them can be measured
this is called ionisation energy because as the electrons are removed the atoms become positive ions
define ionisation energy
ionisation energy is the energies required to remove the electrons one by one from an atom in the gaseous state
define the first ionisation energiy
the first electron needs the least energy to remove it because it is being removed from a neutral atom
define the second ionisation energy
the second electron needs more eergy than the first because it is being removed from a 1+ ion
define the third ionisation
the third electron needs even more energy to remove it because it is being removed from a 2+ ion
what information does the trends in the first ionisation energies give
the trends in the first ionisation energies moving across a period in the periodic table can also give informatio about the energies of electrons in main levels and sub-levels
why do ionization energies increase
ionisation energies generally increase across a period because the nuclear charge is increasing and this makes it more difficult to remove the electrons
despite an increase in nuclear charge what makes it easier to remove electrons
the repulsion between these paired electrons make it easier to remove one of them, despite the increase in nuclear charge
why is their a general decrease ion first ionisation energy going down the group
this is because the outer electron is in a main level that gets further from the nucleus in each case.
whaty happens when the nuclear charge increase going down the group
the positive charge felt by an electron in the outer shell is less than the full nuclear charge.
this is because of the effect of the inner electrons sheilding the nuclear charge
what factors affect ionisation energy
nuclear charge
distance from nucleus
shielding
explain how nuclear charge affects ionisation energy
the more protons there are in the nucleus, the more positively charged the nucleus is and the stronger the attraction for the electrons
explain how the distance from the nucleus affects ionisation energy
attraction falls off very rapidly with distance
an electron close to the nucleus will be much more strongly attracted than one further away
explain how shielding affects ionisation energies
As the number of electrons between the outer electrons and the nucleus increases, the outer electrons feel less attraction towards the nuclear charge
this lessening of the pull of the nucleus by inner shells of electrons is called sheilding
define successive ionisation energies
each time you remove an electron there’s a successive ionisation energy
define high ionization energy
a high ionisation energy means there’s a high attraction between the electron and the nucleus and so more energy is needed to remove the electron
what does a graph of successive ionization energies do
provides evidence for the shell structure of atoms
what happens within each shell
within each shell successive ionization energies increase.
this is because electrons are being removed from an increasingly positive ion
there’s less repulsion amongst the remaining electrons, so they’re held more strongly by the nucleus
when do the bug jumps happen in ionization energy
the big jumps happen when a new shell is broken into
an electron is being removed from a shell closer to the nuclues
what are the trends in the first ionization energies
the first ionization energies of elements down a group of the periodic table decrease
the first ionization energies of elements across a period generally increase
explain why the first ionization energies of elements down a group decrease
if each element down the group has an extra electron shell compared to the one above, the extra inner shells will shield the outer electrons from the attraction of the nucleus
also, the extra shell means that the outer electrons are further away from the nucleus, so the nucleus’s attraction will be greatly reduced
these factors make it easier to remove outer electrons, resulting in a lower ionization energy
explain why ionisation energies increases across a period
the number of protons is increasing, which means a stronger nuclear attraction
all the extra electrons are at roughly the same energy level even if the outer electrons are in different orbital types
so there’s little extra shielding effect or extra distance to reduce the attraction to the nucleus
explain how the sub shell structure creates a drop between groups 2 and 3
using aluminum and magnesium as examples
aluminum outer electron is in a 3p orbital rather than a 3s.
the 3p orbital has slightly higher energy than the 3s orbital, so the electron is, on average, to be found further from the nucleus
the 3p orbital has additional shielding provided by the 3s2 electrons
both of these factors are strong enough to override the effect of the increased nuclear charge, resulting in the ionization energy dropping slightly
what does the pattern in ionization energies provide
provides evidence fro the theory of electron sub-shells
why is there a drop between groups 5 and 6
electron repulsion
explain the drop between groups 5 and 6
the shielding is identical in the phosphorus and sulfur atoms, and the electron is being removed from an identical orbital
in the phosphorus case, the electron is being removed from a singly occupied orbital
but in sulfur, the electron is removed from an orbital containing two electrons
the repulsion between two electrons in an orbital means that electrons are easier to remove from shared orbitals
