Metallic bond Flashcards
reason behind metallic bond
● For any metal atoms, the outermost shell/
valence electron(s) are loosely held by the
nucleus due to low ionisation energy.
● They can then overcome the nuclear
attraction easily and become delocalized,
leaving positive metal ions.
The valence electrons are not shared between two atoms, but they float “freely”
through the giant lattice of metal ions.
definition of metallic bond
The electrostatic attraction between the positive metal ions and the sea of delocalized electrons.
how does the melting point change down group 1 2 and 3
● Ionic radius of metal ion increases
● Charge density decreases
● Weaker electrostatic force of attraction between the metal
ion and the delocalized electrons
● Less energy is required to overcome the attraction
● Melting point decreases
How do the
melting points
change from
group 1 to 13?
● Melting point increases from group 1, 2 to
group 3(13) metals
● Affected by two factors:
(1) Charge of metal ion
(2) Number of valence electrons per
metal atom
How do the
melting points
change from
group 1 to 13? (1)
(1) Charge of metal ions
● As the charge on metal ion becomes greater
● Stronger electrostatic force of attraction to the delocalized electrons
● Larger amount of energy is required to break the attraction
● Increasing melting point
How do the
melting points
change from
group 1 to 13? (2)
(2) Number of valence electrons per metal atom
● Number of delocalised electrons per atom increases
● Stronger electrostatic force of attraction to the positive metal ions
● Larger amount of energy is required to break the attraction
● Increasing melting point
electrical conductivity of metals
● Metals are good conductors of electricity.
● When an electrical circuit is closed, a voltage is set up. The delocalised electrons will be able to move in one direction (from negative to positive).
what is malleability
Malleability refers the ability of being reshaped under pressure.
what is ductility
Ductility refers to the ability of being pulled out
into wires.
why are metals malleable and ductile
When a force is applied to a piece of metal,
● the layers of metal cations can slide past one another
● without breaking the metallic bonds
(because the delocalised electrons still hold the metal cations together)
what are alloys
● Alloys are solid solutions (mixtures) of a metal with other elements.
● Ions of the different metals scattered through the lattice are bound by the delocalized electrons with metallic bonds.
● Alloys have properties that are distinct from their component elements.
example of alloys
brass (Cu copper and Zn zinc)
bronze (Cu copper and Sn Tin)
stainless steel (Fe iron, Ni nickel , Cr chromium)
particle diagram of alloys
● Metal cations have different ionic sizes, thus the regular packing of the metal cations is distorted.
● Layers of metal cations slide less
easily
enhanced properties of alloys
Enhanced properties of alloys
1. Increased strength (harder)
2. Decreased malleability and ductility
3. Lower electrical conductivity (movement of delocalised electrons affected)
