Atomic Structure

Question 1

What is the top number when representing an element?

Answer 1

Mass number/nucleon number

Question 2

What is nucleon number/mass number?

Answer 2

Total number of protons and neutrons in the nucleus of an atom

Question 3

What is the bottom number when representing an element?

Answer 3

Atomic number/proton number?

Question 4

What is atomic number/proton number?

Answer 4

number of protons in the nucleus of an atom

Question 5

What is the characteristics of an atom?

Answer 5

It is electrically neutral, it has the same number of electrons and protons

Question 6

What are isotopes?

Answer 6

Atoms of the same element with the same number of protons but different number of neutrons

Question 7

What are isotopes of the same element similar in?

Answer 7

• Number of electrons
• Number of protons/ Atomic number
• Chemical Properties

Question 8

What do isotopes of the same element differ in?

Answer 8

• Number of neutrons
• Mass number
• Relative atomic mass
• Physical properties

Question 9

What is isotopic?

Answer 9

Atoms or ions that contain the same number of protons

Question 10

What is isoelectronic?

Answer 10

Atoms or ions that contain the same number of electrons

Question 11

What is isotonic?

Answer 11

Atoms or ions that contain the same number of neutrons

Question 12

What is the extent of deflection directly proportional to?

Answer 12

Charge/mass where the mass is the mass number

Question 13

What happens to the extent of deflection when the charge is greater?

Answer 13

When the charge is greater, the extent of deflection is greater because of the stronger electrostatic forces of attraction that pulls it downwards/upwards towards the charge plate

Question 14

What happens to the extent of deflection when the mass is greater?

Answer 14

The extent of deflection is smaller because the heavier ion have larger inertia and is harder to pull it downwards to the negatively charged plate

Question 15

What is an orbital?

Answer 15

A region of space where there is a high probability density or electron density

Question 16

What is the chance of finding an electron in an orbital?

Answer 16

95%

Question 17

What are the characteristics of s orbital?

Answer 17

• Each s subshell contains only one orbital
• Spherical shape
• Non-directional nature
• Equal probability of finding an electron at any given distance
• 0 probability at the nucleus

Question 18

What are the characteristics of p orbital?

Answer 18

• each p subshell has 3 degenerate orbitals (px, py, pz)
• dumbbell shape
• symmetrical along axis
• directional nature
• 0 probability at the nucleus

Question 19

What are the characteristics of d orbital?

Answer 19

• each d subshell has 5 degenerate orbitals
• gives transitional metals their special properties
• 0 probability of finding an electron along dxy, dxz, dyz axes

Question 20

What is the maximum number of electrons each orbital can accommodate?

Answer 20

2

Question 21

What happens to the size of the orbital when it is of a higher energy?

Answer 21

Increases

Question 22

What does a larger n value (principal quantum number) indicate about the energy?

Answer 22

A larger n value indicates a larger orbital which is further away from the nucleus and hence have a higher energy

Question 23

Within a subshell, what energy do orbitals have?

Answer 23

Degenerate (same energy)

Question 24

What is the relative energies of the orbitals?

Answer 24

1s (lowest energy), 2s, 2p, 3s, 3p, 4s, 3d (exception), 4p

Question 25

What is the aim of orbital filling?

Answer 25

Achieve an electronic configuration of the lowest possible energy at the ground state

Question 26

What are the 3 rules in orbital filling?

Answer 26

* Aufbau principle * Pauli Exclusion Principle * Hund's Rule

Question 27

What is Aufbau Principle?

Answer 27

Electrons reside in the orbital of lowest possible energy first (draw the arrow diagram)

Question 28

What is the Pauli Exclusion Principle?

Answer 28

an orbital can accomodate a maximum of 2 electrons and they must be in opposite spins

Question 29

What is the Hund’s rule?

Answer 29

Electrons occupy degenerate orbitals singly and with the same spin before pairing occurs

Question 30

What is the ground state?

Answer 30

The most stable and lowest energy state

Question 31

What are the exceptions to orbital filling?

Answer 31

Cr and Cu because half-filled or fully-filled d subshell tend to be more stable

Question 32

What indicates the number of principal quantum shell?

Answer 32

Period number

Question 33

What is the number of valence electrons equal to?

Answer 33

Group number

Question 34

How to find group number using spdf notation?

Answer 34

- s-block: sum of valence electrons (sum of number of electrons with the highest principal quantum shell number) - p-block: sum of valence electrons + 10 - d-block: sum of d + s electrons

Question 35

Where are the different blocks located?

Answer 35

* s is left two * d is middle * p is right * f is bottom 2 that is separated

Question 36

What do elements in the same group have?

Answer 36

The same valence shell electronic configuration

Question 37

How are electrons removed in cation formation?

Answer 37

Electrons are removed from the outermost shell (4s removed before 3d cause 4s is outer)

Question 38

How are electrons added in anion formation?

Answer 38

Electrons are added to the empty/partially filled outermost orbitals

Question 39

What is ionisation energy?

Answer 39

Energy required to remove 1 mole of electrons from 1 mole of gaseous atoms or ions (for 1st IE it’s atoms, for 2nd IE it’s ions)

Question 40

What is the equation for 1st IE?

Answer 40

X(g) → X⁺(g) + e⁻ ΔH = 1st IE of X

Question 41

What are the factors that affect ionisation energy?

Answer 41

* effective charge (nuclear charge and shielding effect) * atomic radius

Question 42

What is the formula for effective nuclear charge?

Answer 42

Zeff = Z - shielding constant Z: nuclear charge

Question 43

What affects nuclear charge, Z and what are the implications?

Answer 43

* The larger the number of protons, the greater the nuclear charge * as nuclear charge increases, the attraction on electrons increases and more energy is required to remove the valence electron

Question 44

What affects the shielding constant and what are the implications?

Answer 44

* The larger the number of inner principal quantum shell of electrons, the greater the magnitude of shielding constant, the greater the shielding effect

Question 45

What affects atomic radius?

Answer 45

* as number of filled principal quantum shells increases, atomic radius increases * as effective nuclear charge increases, atomic radius decreases

Question 46

How does a larger atomic radius related to ionisation energy?

Answer 46

* A larger atomic radius implies that valence electrons are located further away from the nucleus * as a result, they experience weaker attractive force from the nucleus and can be removed more easily, hence a lower IE

Question 47

How does a larger effective nuclear charge affect ionisation energy?

Answer 47

a larger effective nuclear charge implies that the valence electrons are held more strongly to the nucleus and require more energy to be removed

Question 48

What is the trend of 1st IE across a period?

Answer 48

* 1st IE generally increase across a period * across a period, nuclear charge increases while there is a negligible increase in shielding effect as electrons are removed from the same shell, thus effective nuclear charge increases * atomic radius also decreases * more energy is required to remove the valence electrons that are increasingly more attracted by the positive nucleus

Question 49

What are the anomalies of the trend of 1st IE across a period?

Answer 49

* 2p electrons to be removed from B has a higher energy than 2s electrons to be removed from Be * Coulombic repulsion between paired 2p electrons in O makes it easier to remove one of the paired 2p electrons than an unpaired 2p electron from N

Question 50

What is the trend of 1st IE down a group?

Answer 50

* 1st IE decreases down a group * down a group, atomic radius increases * the increase in shielding effect due to increase in number of principal quantum shells is largely cancelled out by the increase in nuclear charge * less energy is required to remove the valence electrons that become increasingly less attracted by the positive nucleus

Question 51

How to describe trend of successive ionisation energy and how to use it to predict group number?

Answer 51

* there is an increase in successive IE as the electron is removed from an ion of increasing positive charge * first two ionisation energies increase gradually as they only involve the removal of outermost 3s electrons only * sharp increase from 2nd to 3rd IE since it involves the removal of 2p electrons from an inner principal quantum shell * only two electrons in outermost shell, group II element

Question 52

Why is there a sharp increase in IE?

Answer 52

* The electron is removed from an inner principal quantum shell which is located nearer to the nucleus * The electron also experiences lesser shielding effect and greater effective nuclear charge, hence it is more strongly attracted to the nucleus and will require a larger amount of energy to remove