Atomic Structure

Question 1

What are isotopes (isotopic masses)

Answer 1

• atoms of an element that have the same number of protons but different number of neutrons and hence different nucleon number
• different mass numbers of the same element

Question 2

Chemical properties of isotopes

Answer 2

• show similar chemical properties as the number of electrons is the same

Question 3

Relationship of
- angle of deflection and charge of particle
- angle of deflection and mass

Answer 3

• directly proportional
• inversely proportional

Question 4

As principal quantum number increases (distance, attraction, energy level)

Answer 4

• the further is the shell from the nucleus
• the less strongly the electron is attracted to nucleus
• higher the energy level of the electron

Question 5

In each orbital

Answer 5

• contain a maximum of two electrons
• must be in opposite spin

Question 6

Arrangements of electrons

Answer 6

• in the n principal quantum number, there are n number of subshells consisting of n² orbitals with max of 2n²

Question 7

Pauli exclusion principle

Answer 7

• each orbital max of 2 electrons
• must have opposite spins

Question 8

Hunds rule (degenerate orbitals)

Answer 8

• for a set of degenerate orbitals, electrons occupy orbitals singly with parallel spins before any pairing
• minimises inter-electronic repulsion as electron tend to be as far away as possible

Question 9

Afbau principle

Answer 9

• occupy energy with lowest possible energy first
• electrons are in ground state

Question 10

What is iso electronic

Answer 10

• same number of electrons

Question 11

What is ionisation energy

Answer 11

• first ionisation energy of an element is the energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of singly charged gaseous cations

Question 12

How does nuclear charge affect first I.E ( no. of protons, attraction, energy)

Answer 12

• as number of protons increase, nuclear charge increases
• attraction of positively charged nucleus for the negatively charged valence electrons becomes stronger
• more energy is required to remove the valence electron
• I.E increases

Question 13

What is the shielding effect by other electrons

Answer 13

• electrons in inner electronic shells repel those in the outer shell away from the nucleus
• inner electronic shell shield the valence electrons from the attraction of the nucleus

Question 14

How does shielding effect affect I.E (shielding effect, attraction, energy)

Answer 14

• shielding effect increases with an increase in the number of inner electronic shells
• electrostatic attraction between the valence electron and the nucleus becomes weaker
• less energy required to remove valence electron shell
• I.E decreases

Question 15

Exceptions for trend in first I.E across period 2 and 13 (Mg and Al) (nuclear charge, electron, energy)

Answer 15

• nuclear charge of Al is higher than Mg
• 3p electron to be removed from Al is at higher energy level and less strongly attracted to the nucleus than the 3s electron to be removed from Mg
• less energy is required to remove the 3p electron in Al than the 3s electron in Mg
• I.E of Al is lower than that of Mg

Question 16

Exceptions for trend in first I.E across period between 15 and 16 (P and S) (nuclear charge, electron, energy)

Answer 16

• nuclear charge of S is higher than P
• however the 3p electron to be removed from S is a paired electron while that to be removed from P is an unpaired electron
• due to inter-electronic repulsion between paired electron in the same orbital
• less energy is required to remove the 3p electron from S
• first I.E of S is lower than that of P

Question 17

General increases in I.E (electron, proton, electron, energy)

Answer 17

• as electrons are succcessively removed from the atom
• no. of protons remain the same and nuclear charge remains the same
• no. of electrons decreases and shielding effect decreases
• remaining electrons experience stronger attraction by nucleus
• more energy is required to remove the electron leading to increasing I.E

Question 18

Why is third I.E significantly larger than second I.E(Mg) (electron, attraction, energy )

Answer 18

• third electron is removed from the next inner electron shell which is nearer to nd less shielded from the nucleus
• electron experiences even stronger attraction by nucleus
• even more energy is required to remove the electron leading to a larger increase in I.E