Chemistry, Third edition

3 · INSIDE THE ATOM

case, and the main energy levels of atoms possess sublevelsof energy. The sublevels

include the four types s,p,dandf:

s sublevelscontain up to 2 electrons; the electrons are said to be ‘s electrons’.

p sublevelscontain up to 6 electrons; the electrons are said to be ‘p electrons’.

d sublevelscontain up to 10 electrons; the electrons are said to be ‘d electrons’.

f sublevelscontain up to 14 electrons; the electrons are said to be ‘f electrons’.

A full description of a sublevel also requires the principal quantum number n.

For example, the third shell of electrons (n3) contains s, p and d sublevels of

energy, and these are labelled 3s, 3p and 3d. The symbol 3s^1 would show that there

is one electron in the 3s sublevel, and 3p^6 would show that the 3p sublevel is full.

The order in which the sublevels are filled is:

1s 2s 2p 3s 3p 4s 3d...

Low energy High energy

Note that (rather oddly) the 4s sublevel is filled before the 3d. Using superscripts to

show the maximum number of electrons in these levels, the sublevels may be writ-

ten as follows:

1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2...

You are strongly advised to learn this before carrying on!

Note that despite the order of energies of the sublevels, when writingthe elec-

tronic structure of an atom, sublevels with the same value of nare grouped

together (i.e. we write3d before 4s).

Think of the aluminium atom, with an electronic configuration of 2.8.3. A more

detailed description of its energy levels is obtained by feeding all 13 electrons into

the sublevels, giving

1s^2 2s^2 2p^6 3s^2 3p^1

or

[Ne] 3s^2 3p^1

Electronic structure of the ‘first transition series’ of

elements

The elements titanium to copper are known as the first transition series. The elec-

tronic structures of these atoms (and of zinc and scandium) in their lowest energy

states are shown in Table 3.4.

42

Table 3.4Electronic structure of the first transition series of metals

Element and symbol Atomic number Bohr structure s,p,d structure

Scandium 21 2.8.9.2 or [Ar].3 1s^2 2s^2 2p^6 3s^2 3p^6 3d^1 4s^2

or [Ar] 3d^1 4s^2

Titanium 22 [Ar].4 [Ar] 3d^2 4s^2

Vanadium 23 [Ar].5 [Ar] 3d^3 4s^2

Chromium 24 [Ar].6 [Ar] 3d^5 4s^1

Manganese 25 [Ar].7 [Ar] 3d^5 4s^2

Iron 26 [Ar].8 [Ar] 3d^6 4s^2

Cobalt 27 [Ar].9 [Ar] 3d^7 4s^2

Nickel 28 [Ar].10 [Ar] 3d^8 4s^2

Copper 29 [Ar].11 [Ar] 3d^10 4s^1

Zinc 30 [Ar].12 [Ar] 3d^10 4s^2

Electron

configuration of

atoms of the

elements: s,p,d

notation

Complete the last column

of Table 3.3 by entering

the detailed electronic

structures of the first 20

elements using the s,p,d

notation. Learn these

electronic structures!

Exercise 3I