Atomic structure - Mr King

Question 1

why do the first ionisation energies usually increase ACROSS a period (4 points)

Answer 1

.As we move across a period nuclear charge increases (due to increase in protons), this increases the attraction between the nucleus and the electrons

.The stronger attraction between the nucleus and electrons REDUCES ATOMIC RADIUS, making the outer electrons more tightly bound.

.As they are in the same period electrons are added to the same shell meaning the shielding effect will not change across the
period

.The increased energy makes it harder for electrons to be removed, they therefore require more energy, resulting in higher ionisation energy

Question 2

explain why the first ionisation energy decreases down any group on the table
(4 points to be made)

Answer 2

.Number of ELECTRON SHELLS INCREASE DOWN THE GROUPS of the table

.Electrons between the outer electron shell and the nucleus increase, SHEILDING refers to when inner electrons reduce electrostatic forces felt by outer electrons and the nucleus

.This means that there is a GREATER DISTANCE BETWEEN THE OUTER ELECTRONS AND THE NUCLEUS

.Greater distance means that ELECTROSTATIC FORCES BECOME WEAKER making it easier for the first ionisation to occur

Question 3

Why does the ionisation energy between group 2-3 decrease

Answer 3

.The OUTER ELECTRON IN GROUP 3 IS IN A P-ORBITAL whilst GROUP 2’S IS IN AN S-ORBITAL

.The P-orbital electron is slightly further away from the nucleus than the s-orbital

.Therefore less energy is required to remove the first electron from the P-orbital of a group 3 element

Question 4

why does the ionisation energy decrease from group 5-6

Answer 4

.The ionization decreases moving from group5-6 due to the spins of the electrons on the outer shell

.The electrons in group 5 are aligned

.The two opposing spin electrons in an orbital of Group 6 repel each other making it easier for one to be removed (due to interelectronic repulsion)

Question 5

out of Na and K which element has higher first ionisation energy and why

Answer 5

.Na

.the number of electron shells increase down the group, this means more shielding and therefor weaker electrostatic forces between the outer electrons and the nucleus

.resulting in the energy required to remove an outer electron to decrease

Question 6

out of Mg and Al which element has higher first ionisation energy and why

Answer 6

.Mg

.Magnesium has a configuration where the outer electron is in the s-orbital, whereas Aluminium’s is in a p-orbital

.P orbital electrons are slightly further away from the nucleus, this means it has weaker electrostatic forces between the outer electron and the nucleus despite the increased nuclear charge

.Aluminium’s p-orbital outer electron therefore requires less energy to remove

Question 7

out of N and O which element has a LOWER ionisation energy and why

Answer 7

.O

.Due to the number of spins of each element, Nitrogen has has 3 spins aligned

.Whereas Oxygen has on pair of opposite spinning electrons that repel each other, therefore it is easier to remove one of the two and requires less energy

Question 8

define the first ionisation energy

Answer 8

the energy required to remove 1 mole of electrons from each atom of 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

Question 9

what does atomic emission spectroscopy provide evidence for?

Answer 9

quantum shells

Question 10

what do two arrows in a box represent

Answer 10

up and down arrows represent electrons with opposite spins in the same orbital

Question 11

why would all arrows be aligned before pairs are made

Answer 11

electrons are added into separate orbitals first because of Hund’s Rule before pairs

Question 12

iodine and chlorine have similar properties why?

Answer 12

-both have 7 electrons in the outer shell, electronic configuration in outer shell governs their chemical reactions

Question 13

why is Mg higher first ionisation than Na

Answer 13

forces of attraction between the nucleus and outer electron is greater in magnesium

as it has a larger nucleic charge (due to increased proton number) resulting in decreased atomic radius

Question 14

a student suggested that the difference in rates of reaction of strontium and barium with water is due to the difference in the sum of their first and second ionisation energies discuss this suggestion

Answer 14

-sum of first two IE for barium is lower as barium looses its outer elections more easily
-barium has a larger atomic radius as it has more shells
-therefore barium has more shielding
-these outweigh influence

Question 14

what is the pattern of group 3 IE across

Answer 14

up
down
up
up
down

Question 15

Explain the trend in the values of the first ionisation energies for the group containing
sulfur

Answer 15

the 1st ionisation energies decrease down a group as although proton number increases

the electron being removed is further away from the nucleus, resulting in weaker electrostatic forces due to more shielding from middle electron shells

Question 16

explain why the first ionisation energy of hydrogen is less than helium but greater than lithium

Answer 16

. H < He, as helium’s outer electron is located in the same shell as hydrogen

.however He has a larger nucleic charge, this increase in forces of attraction makes the outer electron harder to remove

.H > Li, as lithium’s outer electron is in a higher energy level that hydrogen, further away from the nucleus

.this means there will be greater shielding, causes electrostatic forces to be weaker therefore making it easier to remove an electron from outer shell

Question 17

what are the patterns noticed in ionisation energy (brief)

Answer 17

.1st IE increase across a period due to increasing nuclear charge

.ionisation energy decreases down a group due to increased number of electron shells, that increase shielding, weakening electrostatic forces

.energy decreases from group 2-3 due to outermost electron of group 3 being located in the P-orbital which is further away from the nucleus, causing less energy to be required to remove it

.energy decreases from group 5 - 6 due to the spin of electrons when they fill the orbitals, in group 5 they are aligned, whereas in group 6 there are two opposing spins that repel one another, making it easier for one to be removed

Question 18

define first ionisation energy

Answer 18

the energy required to remove one mole of electrons from each atom of one mole in of gaseous atom to form one mole of gaseous 1+ ions