Chapter 4- Structure

Question 1

What is meant by the term ‘isotope’?

Answer 1

Isotopes are atoms of an element that have the same number of protons and electrons but different numbers of neutrons

Question 2

Which sub-atomic particles are present in the nuclei of atoms?

Answer 2

Positively charged protons and neutral neutrons. Both have a relative mass of 1

Question 3

In a neutral atom, what’s the ratio of electrons to protons?

Answer 3

1:1. This is because electrons have a relative charge of -1 and protons are +1

Question 4

Why is the chemistry of an atom not affected by being an isotope?

Answer 4

They don’t have a charge, so don’t affect how protons and electrons interact

Question 5

What does change between isotopes?

Answer 5

Physical properties, like mass, and melting and boiling points

Question 6

How does alpha decay convert one atom to another?

Answer 6

A helium nucleus is released, reducing the mass number by 4 and atomic number by 2. The new atom has a charge of 2-.

Question 7

How does beta decay convert one atom to another?

Answer 7

A neutron turns into a proton, and an electron leaves the atom. The mass number stays the same but the atomic number increases by 1. The charge is 1+

Question 8

Energy=

Answer 8

frequency x Planck’s constant (6.626*10^-34)

Question 9

Speed of light (2.998*10^8)=

Answer 9

frequency x wavelength

Question 10

How is E=hv combined with c=vλ?

Answer 10

v=c/λ

∴ E=hc/λ

Question 11

How is the energy of a photon converted into energy per mole?

Answer 11

Times by Avogadro’s constant (6.022*10^23)

Question 12

What are the four quantum numbers that can be assigned to electrons?

Answer 12

Principal QN, azimuthal QN, magnetic QN, spin QN

Question 13

What does the principle quantum number (n) represent?

Answer 13

The energy level

Question 14

What values can the principle quantum number take?

Answer 14

1, 2, 3, …, ∞

Question 15

What does the azimuthal quantum number (ℓ) represent?

Answer 15

The angular momentum of an atomic orbital (orbital type)

Question 16

What values can the azimuthal quantum number take?

Answer 16

0, 1, 2, …, (n-1)

Question 17

What does the magnetic quantum number (ml) represent?

Answer 17

The orientation of orbital in space (the specific orbital)

Question 18

What values can the magnetic quantum number take?

Answer 18

-ℓ to +ℓ, inclusive of zero

Question 19

What does the spin quantum number (ms) represent?

Answer 19

Which way the electron is spinning

Question 20

What values can the spin quantum number take?

Answer 20

±0.5

Question 21

State the aufbau principle

Answer 21

The aufbau principle states that in the ground state of an atom/ion, electrons fill atomic orbitals of the lowest available energy levels before filling higher levels

Question 22

What is the Pauli exclusion principle?

Answer 22

Electrons in the same atom can’t have the exact same four quantum numbers

Question 23

State Hund’s first rule

Answer 23

Every orbital in a sublevel is singly occupied before any orbital is doubly occupied. All of the electrons in singly occupied orbitals have the same spin (to maximize total spin).

Question 24

What do boundary surface diagrams represent?

Answer 24

Boundary surface diagrams are a good representation of shapes of atomic orbitals. Boundary surface diagrams are considered an acceptable approximation of shape of orbital if the boundary surface encloses the region with probability density of more than 90%.

Question 25

What are some of the features of boundary surface diagrams?

Answer 25

1) Shape of the surface diagram: It changes depending on the azimuthal quantum number
2) Size of the surface diagram: The boundary surface diagram of an orbital increases in size as principle quantum number increases
3) Nodes in the surface diagram: Nodes are the region where the probability density goes to zero. There are (n-1) nodes in the boundary surface diagram of all orbitals

Question 26

Why do boundary surface diagrams never have a probability density of 100%?

Answer 26

At any distance from the nucleus, the probability of finding an electron is never zero. It will always have some finite value, so it’s not possible to draw a boundary surface diagram which encloses the region with 100% probability density

Question 27

Describe what is meant by electron shielding

Answer 27

The shielding effect describes the attraction between an electron and the nucleus in any atom with more than one electron shell. It can be defined as a reduction in the effective nuclear charge on the electron cloud, due to a difference in the attraction forces of the electrons on the nucleus

Question 28

What’s the difference between valence and core electrons?

Answer 28

Valence electrons may participate in chemical reactions, while core electrons do not. This is because valence electrons are accessible, and core electrons are inaccessible

Question 29

Describe an ambiguity of valence and core electrons for elements in the d and f blocks

Answer 29

The nearly equal energies of ns and (n - 1)d orbitals. The definitions of core and valence electrons do not depend on whether the electrons are used in chemical reactions, but rather whether they are in an accessible energy level or not.

Question 30

What is the shape of s orbitals?

Answer 30

Spherical

Question 31

What is the shape of p orbitals?

Answer 31

Dumbbell shaped, aligned on either the x, y, or z axis

Question 32

What is the shape of the d orbitals?

Answer 32

Four of the d orbitals are butterfly shaped, and one has an unusual shape that looks like a doughnut surrounding a Q-tip

Question 33

Define the term ‘node’

Answer 33

Nodes are the points in space around a nucleus where the probability of finding an electron is zero.

Question 34

What are the two types of node?

Answer 34

Radial nodes and angular nodes.

Question 35

What are radial nodes?

Answer 35

A radial node occurs when the radial wavefunction is equal to zero, which occur inside the orbital lobes

Question 36

What are angular nodes?

Answer 36

An angular node is a region where the angular wavefunction is zero. In the case of the p-orbitals, this is a plane, although angular nodes are not necessarily planes.

Question 37

How do you work out the number and type of nodes for an orbital?

Answer 37

Number of nodes= n - 1
Angular nodes= ℓ
Radial nodes= (number of nodes) - (angular nodes)

Question 38

How many nodes exist in the first shell?

Answer 38

For the first shell, n=1, which means the number of nodes will be 0.

Question 39

How many nodes exist in the second shell?

Answer 39

For the second shell, n=2, which yields 1 node. 2s orbital: ℓ=0, which means the node will be radial. 2p orbital: ℓ=1, which means the node will be angular

Question 40

How many nodes exist in the third shell?

Answer 40

The third shell, n=3, yielding 2 nodes. 3s orbital: ℓ=0 meaning no angular nodes, and thus the two nodes must be radial. 3p orbital: one angular node, meaning there will be one radial node as well. 3d orbital: two angular nodes, and therefore no radial nodes