Metallic bonds

metallic bonds

• metal atoms packed tightly together in a lattice

• when in lattice structures, the valence electrons are free to move around throughout the structure

  • these are delocalised electrons and are not bound to their atom

• when electrons are delocalised, metal atoms become positively charged

• positive charges repel eachother and keep the lattice in place

• very strong electrostatic forces between positive metal atoms and “sea” of delocalised electrons

malleability

• metals are malleable

• when a force is applied, metal layers can slide

• attractive forces between the cations and electrons act in all directions

• when layers slide, the metallic bonds are reformed

• the lattice is not broken, it just changes shape

electrical conductivity

• metals can conduct in the solid or liquid state

  • there are mobile electrons which can freely move around and conduct electricity

• ability to conduct increases across a period

  • because valence electrons increase across a period

thermal conductivity

• good thermal conductors

• when metals are heated, cations in the metal lattice vibrate more vigorously as their thermal energy increases

  • vibrating cations transfer their KE to adjacent cations by colliding, therefore conducting heat

• delocalised electrons are free to move around, so when cations vibrate, they transfer KE to the electrons

  • delocalised electrons carry this increased KE and transfer it throughout the metal

charge on a metal ion (strength of bond)

• the greater charge on a metal ion, the more electrons in the sea of delocalised electrons and the greater the charge difference between the cations and electrons

• greater charge = strong electrostatic attraction, stronger bonds

• mpt increases across a period due to more electrons

radius of a metal ion (strength of bond)

• metal ions with a smaller ionic radii exert a greater attraction on the sea of delocalised electrons

• greater attraction = stronger metallic bond

• mpt decreases down a group, as the ionic radii increases

high mpt in transition metals

• transition metals are elements with an incomplete d-subshell

• the ability to delocalise d electrons means transition metals have a greater electron density

  • electrostatic forces are strengthened between cations and delocalised electrons

conductivity in transition metals

• large number of delocalised electrons

• more electrons are able to move when a voltage is applied