Download Schrodinger models of the atom

VCE CHEMISTRY UNIT 1
SCHRODINGER’S MODEL OF THE ATOM
Schrödinger’s model of the atom is known as the quantum mechanical model.
Quantum mechanics places the electrons in orbitals, not fixed orbits.
Orbitals are regions of space. The electrons are like a cloud of negative charge within
that orbital. The electron shells proposed by Bohr are still used, but the electrons in each
shell are not all equal in energy. The shell has subshells.
The quantum mechanical model is a complex mathematical theory with several key
descriptive features:
 Within an atom are major energy levels called shells.
Each shell is assigned a number (called the principal quantum number), starting at
the nucleus and increasing outwards (1, 2, 3...).
 The maximum number of electrons for any shell is given by the formula 2n2
where n stands for the shell number, for example, for shell number 3,
2 X (3)2 = 18 electrons maximum.
 Within the shells are energy levels called subshells.
They are assigned the letters s, p, d, f .
The letter labels come from the study of emission spectra and the appearance of the
lines in spectra, (s = sharp, p = principal, d = diffuse and f = fine.)
 Within a shell, the energies of the subshells increase in the order s,p,d,f
 Within subshells, electrons move in regions of space called orbitals.
There are different types of orbitals. The s type orbitals are spherical, but the
shapes of the other orbitals are complex and will be discussed in Year 12.
 Subshells contain different numbers of orbitals.
The s subshell contains 1 orbital, the p subshell 3 orbitals, the d subshell 5 orbitals
and the f subshell 7 orbitals.
 The Pauli exclusion principle (proposed by the Austrian scientist Wolfgang Pauli)
states that orbitals can hold 0, 1 or 2 electrons.
SHELLS, SUBSHELLS AND ORBITALS
Shell number Types of subshells Electron numbers Maximum number
and arrangement of electrons
1
s
1s2
2
2
s,p
2s2 2p6
8
3
s,p,d
3s2 3p6 3d10
18
4
s,p,d,f
4s2 4p6 4d10 4f14
32
ELECTRON CONFIGURATION
Using the quantum mechanical model of the atom the representation of electron
configurations of atoms can be extended to include shells, subshells and orbitals.
An atom achieves maximum stability, (the lowest energy or ground state), when
electrons are in orbitals of the lowest possible energy. The order of energy levels is
shown below, and may be remembered using the pattern illustrated.
Calcium with 20 electrons has electron configuration 1s22s22p63s23p64s2. This explains
the Bohr configuration of 2,8,8,2 rather than 2,8,10.
For Vanadium with 23 electrons it is 1s22s22p63s23p63d34s2
CLASS QUESTIONS
1.
Give the full electronic configurations of the following elements according to both
the Bohr and Schrodinger models of the atom.
Elements of atomic number:
2.
(a)
3
(b) 15
(c) 17
(d)
19
(e) 26
(f) 35
(a)
Examine a Periodic Table. Explain why Groups 1 and 2 are often called the
s block, and Groups 3 to 12 the d block, and Groups 13 to 18 the p block
(b) What name would you give to the lanthanide and actinide elements?
3.
Identify the atoms that have the following electronic configurations, and state
whether they are in their ground state or an excited state.
(a)
1s2 2s2 2p6 3s1
(b)
1s2 2s2 2p6 3s2 3p5
(c)
1s2 2s2 2p6 3s1 3p6
(d)
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 5s2
(e)
1s2 2s2 2p6 3s2 3p6 3d2 4s2
(f)
(g)
1s2 2s2 2p6 3s2 3p6 3d5 4s2
1s2 2s2 2p6 3s2 3p6 3d9 4s2
4.
Write the electronic configuration for the following commonly occurring ions:
(a)
Na+
(b) Ba2+
(c) Al3+
(d) O2-
(e) Br-