5.3 atomic structure pt2 🏘

Question 1

define first ionisation energy

Answer 1

first ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms of the element to form one mole of singly positively charged gaseous ions (cations)

Question 2

define second ionisation energy

Answer 2

second ionisation energy is the energy required to remove one mole of electrons from one mole of singly positively charged gaseous ions to form one mole of doubly positively charged gaseous ions

Question 3

list the factors affecting ionisation energy

Answer 3

1) nuclear charge
2) screening effect (together with 1, effective nucleur charge)
3) distance between nucleus and electron being removed

Question 4

define nuclear charge and what affects it

Answer 4

nuclear charge refers to the electrostatic attraction between the protons in the nucleus of an atom and the surrounding electrons

affected by the number of protons and the orbital in which the electron is found in

Question 5

define screening effect and what affects it

Answer 5

screening effect refers to the partial decrease in electrostatic attraction between the nucleus and its valence electrons due to repulsive forces from other electrons present

affected by the number of inner shells (not affected within the same shell)

Question 6

explain why there is a general increase in successive ionisatione energy values in the same atom

Answer 6

since number of protons is constant, nuclear charge remains unchanged. as electrons are being removed, the increasingly positive ion attracts its remaining valence electrons more strongly, increasing the amount of energy required to remove each remaining valence electron, resulting in higher successive ionisation energy

Question 7

explain why there is a significant increase from first to second ionisation energy of 2s22p1 atom

Answer 7

the 2nd ionisation energy involves the removal of a 3p electrons from an inner shell that experiences a stronger electrostatic attraction with the nucleus compared to the outermost 4s electron for the 1st IE. more energy is required to remove the 3p electron than the 4s electron, resulting in a higher 2nd IE.

Question 8

given a significant jump from 2nd to 3rd IE, deduce the group number of the element

Answer 8

since the largest increase in IE is between the 2nd and 3rd IE, the third electron is removed from an inner shell while the second electrons is from the valence shell. Thus, the element has two valence electrons and belongs to group 2.

Question 9

explain why the 1st IE decreases down the group

Answer 9

down the group, number of electronic shells increase, which leads to an increase in screening effect and each successive element has its valence electrons located in a shell with a higher principal number. hence, valence electrons are increasingly further away from the nucleus and are less strongly attracted to the nucleus, despite the increase in nuclear charge.
smaller amount of energy is required to remove the valence electron.

Question 10

explain why atomic radius decreases across the period, and 1st IE increases across the period

Answer 10

across the period, electrons are added to the same valence shell, hence screening effect remains approximately constant and increase in nuclear charge outweights negligible increase in screening effect. hence effective nuclear charge increases across the period and there is stronger electrostatic forces of attraction between nucleus and valence electrons, pulling valence electrons closer to the nucleus.

more energy is required to remove the valence electron.
(noble gases exception)

Question 11

what are some exceptions to 1st IE increasing across period and why?

Answer 11

Mg > Al: smaller amount of energy needed to remove 3p electron further away from nucleus compared to 3s electron

P > S: half-filled P more stable; there exists inter-electronic repulsion between paired electrons in S, hence smaller amount of energy

+ lower periods