Atomic Orbitals, Electronic Configurations and the Periodic Table

Question 1

How can the discrete lines observed in atomic spectra be explained?

Answer 1

If electrons, like photons, also display the properties of both particles and waves

Question 2

How do electrons behave in an atom?

Answer 2

As standing waves. These are waves that vibrate in time but do not move in space.

Question 3

What are the different sizes and shapes of standing wave around the nucleus known as?

Answer 3

Orbitals

Question 4

How many electrons can orbitals hold?

Answer 4

A maximum of 2

Question 5

What are the different shapes of orbitals?

Answer 5

s, p, d, f

Question 6

Electrons within atoms have fixed amounts of energy called…

Answer 6

Quanta

Question 7

What is the principal quantum number, n?

Answer 7

Indicates the main energy level for an electron
Higher n = bigger s orbital

Question 8

What is the angular momentum quantum number, l?

Answer 8

Determines the shape of the subshell and can have values from 0 to (n − 1)

Question 9

What is the magnetic quantum number, ml?

Answer 9

Determines the orientation of the orbital and can have values between −l and + l

Question 10

What is the spin magnetic quantum number, ms?

Answer 10

Determines the direction of
spin and can have values of +1/2 or −1/2

Question 11

What is the aufbau principle?

Answer 11

Electrons fill orbitals in order of increasing energy

Question 12

What is Hund’s Rule?

Answer 12

When degenerate orbitals are available, electrons fill each singly, keeping their spins parallel before spin pairing starts (this is to maximise the number of parallel spins or increase spin multiplicity)

Question 13

What is the Pauli Exclusion Principle?

Answer 13

No two electrons in one atom can have the same set of four quantum numbers, therefore, no orbital can hold more than two electrons and these two electrons must have opposite spins

Question 14

In an isolated atom the orbitals within each subshell are…

Answer 14

Degenerate

Question 15

What does it mean if an atom is in the s block of the periodic table?

Answer 15

It’s outermost electron is in an s orbital

Question 16

What does it mean if an atom is in the p block of the periodic table?

Answer 16

It’s outermost electron is in a p orbital

Question 17

What does it mean if an atom is in the d block of the periodic table?

Answer 17

It’s outermost electron is in a d orbital

Question 18

What does it mean if an atom is in the f block of the periodic table?

Answer 18

It’s outermost electron is in a f orbital

Question 19

Why does nitrogen have a higher ionisation energy that oxygen?

Answer 19

The electron is being removed from a half full p orbital in nitrogen, this is a stable electron arrangement

Question 20

Why does boron have a lower ionisation energy than beryllium?

Answer 20

The electron being removed from beryllium is being removed from a full s orbital which is a stable electron arrangement
The electron being removed from boron is further away from the nucleus

Question 21

How can the number of electron pairs surrounding a central atom be found?

Answer 21

• taking the total number of valence (outer) electrons on the central atom and adding one for each atom attached
• adding an electron for every negative charge
• removing an electron for every positive charge
• dividing the total number of electrons by two to give the number of electron pairs

Question 22

Electron pairs are negatively charged and repel each other. They are arranged to…

Answer 22

Minimise repulsion and maximise separation

Question 23

The arrangement of electron pairs around a central atom is…

Answer 23

• linear for two electron pairs
• trigonal planar for three electron pairs
• tetrahedral for four electron pairs
• trigonal bipyramidal for five electron pairs
• octahedral for six electron pairs

Question 24

Electron pair repulsions decrease in strength in the order. What is meant by this?

Answer 24

non-bonding pair/non-bonding pair > non-bonding pair/bonding pair > bonding pair/bonding pair