Ionisation energy and atomic radius - atomic theory 7 - LC chem

Atomic radius def

Half the distance between the nuclei of two singly bonded atoms of the same element

Atomic radius going across a period..

Decreases

Why is there a decrease in atomic radius going across a period

• increase in nuclear charge

• No change in energy levels so screening effect of completed energy levels remains the same

• therefore outer electrons held closer to nucleus as positive nucleus pulls negative electrons towards itself

Atomic radius going down a group

increases

Why does atomic radius increase going down a group

• increase in number of energy levels

• screening effect of electrons in inner energy levels block some of the pull the nucleus has on outer electrons

• outer electrons further away, therefore less closely held, leading to larger atomic radius

first ionization energy

minimum amount of energy required to remove first most loosely bound electron from a mole of isolated atoms of an element in its neutral gaseous ground state

trends for ionisation energy

increase going across a period

decrease going down a group

explain why there is an increase in ionisation energy across a period

due to an increase in the effective nuclear charge and no change in screening effect

Why is there a decrease in ionisation energy going down a group

• Increase in atomic radius due to extra shells being added, inner completed shells screen out some of the nuclear attraction

metals + oxygen

form metal oxide

flourine and chlorine are

yellow green gasses

account for difference in ionisation energy between . and .

• radius size

• stability of energy shell

• stability of sublevel

• second / subccessive ionisation energies

How does distance from the nucleus effect ionisation energy

• smaller atomic radius, more energy required to remove the electron as positive nucleus will have a greater hold on electron

How does stability of energy level impact

full sublevel is most stable, next most stable is half full

checklist for questions w ionisation energy

• distance of electron from nucleus

• stability of sublevel

• stability of shell from which electron is being removed

• removing electron from ion or atom

why is the second electron always harder to remove

because you are now removing from an ion, nuclear charge hasnt changed but since you removed an electron, more nuclear energy is shared between the electrons left

second ionisation energy formula

X⁺_(g) - e^- = x⁺²_(g)

is the second ionisation energy of an element always greater than the first

yes, first electron is removed from an atom, 2nd is removed from an ion, effective nuclear charge in an ion is greater so more energy is needed

state and explain the trend in atomic radius across the second period of the periodic table

decreases due to an increase in effective nuclear charge and no change in screening effect