Chapter7 The periodic table and ionisation energy Flashcards
How is the periodic table arranged
By increasing proton number
periodicity?
Repeating trend in properties of elements across each period
Name for group one elements (Li onwards)
alkali metals
Name group 2
Alkaline earth metals
Name group 7
Halogens
name group 0
noble gases
What does period number describe
The principle quantum number of the highest energy electron shell in an elements atom
What do elements in the same group have in common regarding electrons
Same number of electrons in their outer shell and in each sub shell
what gives elements in a group their similar chemical properties
their similar electron structures
what did Mendeleev do to the periodic table of elements ordered by atomic mass
Leave gaps for undiscovered elements
Predict the properties of those elements based on the surrounding
Swap the order of some elements so they fit into groups based on properties
First ionization energy?
Energy required to remove one electron from each atom in one mole of gaseous atoms of an element
unit for first ionization energy?
kJ mol-1
factors affecting ionization energy
Atomic radius, nuclear charge inner shell shielding
How does atomic radius affect ionization energy
The greater the distance between the nucleus and outer shell the weaker the attraction on outer shell electrons therefore less energy req to remove electron
how does nuclear charge affect ionization energy
More protons in the atom, greater attraction to outer shell electrons so req more energy to move electrons
how does inner shell shielding affect ionization energy
The shielding effect reduces the attraction between the nucleus and outer shell electrons. More inner shells means less energy required to remove an electron
shielding affect?
Idea that inner shell electrons repel outer shell electrons
group trends in first IE
FIE decrease going down a group
FIE increase across a period
why does FIE decrease down a group
Atomic radius increases
More inner shells so shielding increases
Overall nuclear attraction decreases
why does FIE generally increase across a period
Nuclear charge increases
Atomic radius decreases ( not bc of number of shells but bc a more positive nucleus will attract the electrons more)
Overall nuclear attraction increases
Between which elements are there anomalies in the increasing of FIE across a period
Berillium to Boron
Nitrogen to Oxygen
There is a decrease in FIE rather than an increase
what is the reason for the decrease of FIE from beryllium to boron
Boron marks the start of filling th p6 sub shell, it has 1 electron in this sub shell. Bc the 2p has more energy than 2s it is easier to remove the outer 2p electron in boron than the 2s electron in Be
what causes the decrease in FIE from N to O
O Mark’s the start of spin pairing electrons in the 2p orbital, it is easier to remove a spin paired electron because of the repulsion that it experiences
successive ionization energy?
like first ionization energy but is the energy required to remove the following electrons (an element can have as many successive IE as it has electrons)
How many outer shell electrons are removed at a time in relation to successive IE
one at a time
how does the successive IE change as the number increases ( 2nd to 3rd to 4th etc)
It increases bc after an electron is lost, the remaining electrons are pulled closer to the nucleus so the nuclear attraction on the remaining electrons has increased so they require more energy to remove
what can first and successive IE provide evidence for
The different electron energy levels (shells) in an atom
On an IE graph what characterises a change in shells
A large difference in ionization energy bc the next shell is much closer to the nucleus so attraction is higher so electrons require more energy to remove
on an IE graph what characterises the number of electrons in a shell
the IEs increasing by small increments
