Transcript THE GASEOUS STATE

ELECTRONIC
CONFIGURATION
PERIODICITY OF ELEMENTS
PERIODIC TABLE
• Most powerful tool in the study of
chemistry.
• Order the elements by Z number.
• Used to predict undiscovered elements and
their properties. (Recall recent discoveries
of atoms with Z = 113, 115)
• Periodicity is explained by quantum
mechanics.
From H to Multielectron Atoms
• In H, AOs with the same n have the same E.
• In multielectron atoms,
– For a given set of QNs, orbital energies are
lower than in H (larger Z value).
– AOs with the same n value but different ℓ have
different energies (nondegenerate).
– orbitals with the same n and ℓ have the same E.
– 3d and 4s have similar energies
DETERMINING ELECTRONIC
CONFIGURATIONS
• There are four quantum numbers [n, ℓ, mℓ,
ms] which have defined relationships to
each other
• These 4 QNs are used to define a set of
atomic orbitals that electrons fill.
• Aufbau (building-up) Principle determines
the order of filling AOs; i.e. the electronic
configuration of the atom.
ELECTRON CONFIG. (2)
• Aufbau Prin. says that electrons fill AOs to
achieve the lowest energy (atom’s ground state).
• Electrons fill the lower energy AOs before filling
the higher energy AOs.
• Pauli Exclusion Principle: Max of 2 electrons per
orbital; i.e. electron spins oppose and no two
electrons can have the same 4 q.n. values in an
atom.
ELECTRON CONFIG. (2)
• Hund’s Rule: When filling orbitals of identical
energy, fill the empty orbitals with one electron
before pairing them up; I.e. maximize number of
unpaired spins.
• There are exceptions: e.g. 4s fill before 3d; Cr, Cu
have a single 4s electron and fully- or half-filled
3d orbitals (extra stability).
• Electron configs. of cations (remove from largest
n AO) and anions (add according to Aufbau Prin.)
ELECTRON CONFIG. (3)
• electron config, orbital-filling diagram,
noble gas core for [the inner electrons] +
valence electrons (VE).
• VEs are the outermost electrons and the
most important ones in chemical bonding.
• Learn electron config.s through Kr; use PT
to identify VEs of atoms beyond Kr. (Fig
5.17)
PERIODIC LAW
• Now we can see how the electronic
configurations of atoms lead to periodicity
of elements and form the basis for chemical
and physical properties of elements.
• PERIODIC LAW: When the elements are
arranged according to Z, their physical and
chemical properties vary periodically,
regularly and predictably.
PERIODIC LAW (2)
• Elements in the nth A-Group (Main Group)
have n electrons in the valence (outermost
occupied) shell.
• Elements in the nth period have n as the
principal QN of its valence shell.
PERIODIC LAW (3)
• Fig 5.18 shows how the Periodic Table can
be used to determine electron config.
– Main Group: s- and p- block elements
– Transition Group: d-block elements
– Lanthanide and Actinide: f-block elements
• Note filling order on p 186.
PERIODICITY OF ATOMIC
PROPERTIES
• Atomic Radius, Size (Figs 5.1, 5.19, 5.20)
– lower LH corner
• Ionization Energy (Figs 6.3, 6.4, 6.5; Table
6.2)
Atom (g) -----> Ion+(g) + electron
– upper RH corner
• Electron Affinity (Fig 6.6)
Atom (g) + electron -----> Ion- (g)
– upper RH corner
PERIODICITY OF ATOMIC
PROPERTIES (2)
• Metallic Character
– lower LH corner
• Nonmetallic Character
– upper RH corner
PERIODICITY OF ATOMIC
PROPERTIES (3)
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Flame colors
Oxidizing agents (Group 7A)
Reducing agents (s-block)
Acidic Oxides (upper RH corner)
Basic Oxides (lower LH corner)
Amphoteric Oxides (in between)