Structure 2.3 Metallic Bonds

Structure of metallic elements

lattice of cations surrounded by delocalized electrons

Define metallic bonding

electrostatic attraction between lattice of cations and delocalized electrons

Describe the ionization energy of metal atoms

low ionization energy

Explain the reason behind the description of metal atoms’ ionization energy

(when looking at elements within a period)
metal atoms relatively have less protons and electrons ∴less nuclear charge ∴less attraction between the nucleus and electrons ∴easier to remove electrons

→ metal atoms are bigger in size (less nuclear charge ∴ electrons are further away from the nucleus)

how do metal atoms react with other elements

losing valence electrons and forming positive ions (cations)

What determines the metallic character of elements?

loss of control over valence electrons + sea of delocalized electrons

Define delocalized electrons

valence electrons of metal atoms that are not associated with one specific electron nucleus but move freely among a lattice of cations

What determines the physical characteristics of metallic elements?

delocalized electrons

State some of the common physical characteristics metallic elements share.

• good electrical conductivity

• good thermal conductivity

• malleability

• ductility

• high melting points

• high boiling points

• shiny, lustrous appearance

Explain why metallic elements are good electrical conductors.

• delocalized electrons are highly mobile

  • electrons are considered electricity

    • when voltage is applied (negative and positive terminals are added to metals), electrons freely move in one direction from the negative terminal toward the positive terminal

Explain why metallic elements are good thermal conductors.

• when heat is applied, particles vibrate

• delocalized electrons easily influence other particles to vibrate since they are mobile

• heat energy from the vibration is delivered all throughout the metal

Describe malleability

physical property of elements that can be shaped under pressure

Explain why metallic elements are malleable and ductile.

• delocalized electrons are non-directional therefore movement is random

• when under pressure, metallic bond still remains since electrons can move freely and prevent repulsion between cations

Describe ductility.

Physical property of elements to be drawn our into threads.

Explain why metallic elements have high melting points and boiling points.

• delocalized electrons are easily evenly distributed among cations ∴stronger bonds

  • more energy is needed to overcome the electrostatic forces in the metallic bond

Explain why metallic elements have shiny, lustrous appearances.

• delocalized electrons in the metal crystal structure reflect light

What nature or feature of metallic bonding allows the creation of alloys?

Non-directional

Define alloys.

• mixture of metal with other metals or non-metal elements (in a molten state) (homogenous)

• enhances the properties of metallic elements

What does the strength of metallic bonds depend on?

Charge and radius of metal ions

What is the order of importance when determining the strength of metallic bonds?

respectively,

• # of delocalized electrons (valence electrons)

• charge of cations (metal ions)

• radius of cations (metal ions)

What determines a stronger bond/ greater electrostatic attraction between metal cations and delocalized electrons?

• more delocalized electron density (more valence electrons)

• smaller cation (high nuclear charge, more protons)

What can be used to confirm the strength of metallic bonds?

melting point

trend in metallic bonding strength from left to right across a period:

• ↑# electrons

  • ↑ delocalized electron density

• ↑# protons

  • ↑nuclear charge

  • ↓ size of atom

  • ↑ electrostatic attraction between delocalized electrons and cations

    • ↑ ionization energy

    • ↓ reactivity

• ↑ melting point

• ↑STRENGTH

trend in metallic bonding strength down a group:

• ↑ shielding

  • ↑ radius of metal atom

• ↓ ionization energy

  • ↑ reactivity

• ↓melting point

• ↓STRENGTH

Define transition elements

• Elements with an incomplete d sublevel

• Elements that can lead to cations with an incomplete d sublevel )d sublevel elections are delocalized)

Explain the reason behind high melting points of transition metals.

• ↑of electrons in d sublevel

  • ↑of delocalized electrons

• ↑ of protons

  • ↑nuclear charge (positive charge)

  • ↓size

  • ↑electrostatic attraction

Explain the lack of clear trends between transition metals.

• All of them:

  • can lose ↑# of electrons (have ↑ # of delocalized electrons)

  • have ↑ positive charge (nuclear charge)

    • ↓size

Explain why transition metals have high electrical conductivity.

• ↑# of delocalized electrons (mobile)