Atomic Orbitals, Electronic configurations and the Periodic table

Question 1

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

Answer 1

The discrete lines observed in atomic spectra can be explained if electrons, like photons, also display the properties of both particles
and waves

Question 2

What are the different orbital shapes?

Answer 2

s (sphere)
p (Single dumbell)
d (Double dumbell or dumbell and doughnutt)
f (other complex shapes)

Question 3

Electrons have fixed amount of energy called…

Answer 3

Quanta

Question 4

It is possible to describe electron in an atom using?

Answer 4

The four quantum numbers

Question 5

What are the four quantum numbers?

Answer 5

♦ the principal quantum number n indicates the main energy level
for an electron and is related to the size of the orbital
♦ the angular momentum quantum number l determines the shape of the subshell and can have values from zero to n −1
♦ the magnetic quantum number ml determines the orientation of the orbital and can have values between −l and +l
♦ the spin magnetic quantum number ms determines the direction of spin and can have values of +1/2 or -1/2

Question 6

Electrons within atoms are arranged according to?

Answer 6

♦ the aufbau principle — electrons fill orbitals in order of increasing energy (‘aufbau’ means ‘building up’ in German)
♦ Hund’s rule — when degenerate orbitals are available, electrons fill each singly, keeping their spins parallel before spin pairing
starts
♦ the Pauli exclusion principle — 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 7

What does degenerate mean?

Answer 7

Of the same energy

Question 8

How can the variation in first, second and subsequent ionisation energies with
increasing atomic number for the first 36 elements can be explained?

Answer 8

In terms of the relative stability of different subshell electronic
configurations. This provides evidence for these electronic
configurations. Anomalies in the trends of ionisation energies can be explained by considering the electronic configurations.

There is a special stability associated with half-filled and full subshells. The more stable the electronic configuration, the higher the ionisation energy.

Question 9

The number of electron pairs surrounding a central atom can be found by?

Answer 9

♦ 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 10

What are electron pairs charge? What does this create?

Answer 10

Electron pairs are negatively charged and repel each other. They are arranged to minimise repulsion and maximise separation.

Question 11

What is the arrangement of electron pairs around a central atom?

Answer 11

♦ 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 12

Shapes of molecules or polyatomic ions are determined by?

Answer 12

the shapes adopted by the atoms present based on the arrangement of electron pairs. Electron dot diagrams can be used to show these arrangements

Question 13

Electron pair repulsions decrease in strength in the order?

Answer 13

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

Question 14

The periodic table is subdivided into four blocks what are these? What do they correspond to?

Answer 14

s, p, d and f
corresponding to the outer electronic configurations of the elements
within these blocks.

Question 15

Electron orbitals fill in the order?

Answer 15

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 6d, 5p