Structure 2.3 - Metallic
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How are delocalised electrons in metallic bonds formed?
outer electrons strongly attracted to neighbouring atoms, moving through empty spaces in the lattice become shared among all metal atoms
What keeps the neatly arranged metallic lattice in place?
repulsion between cations
What is the metallic bond?
strong electrostatic forces between lattice of cations and delocalised e-
Why is metallic bonding different from ionic or covalent?
bonding is not between atoms/ions: it is between cations and delocalised e-
What is the type of bonding in metallic bonding?
non-directional: electrostatic attractive force occurs in all directions
What are 6 typical properties of metals?
• shiny • sonority • malleable • ductile • electrical conductors • thermal conductors
Why do metals look shiny?
delocalised e- interact with visible light, absorbing some of the energy and vibrating this vibration generates a 2nd wave of light radiating from the surface, reflecting the light
Why are metals sonorous?
when struck, delocalised electrons propagate the sound easily due to their free movement
What is the relationship between sonority and density in metals?
Lower density metals have more space between cations for the delocalised electrons to move, making them more sonorous
Why are metals malleable and ductile?
non-directional bonding layers within the lattice shift when stress is applies shifting layers does not affect metallic bond (cations/electrons)
Why do metals conduct electricity?
delocalised electrons can move around when potential energy is supplied, they can be repelled or attracted
What is the relationship between number of valence electrons in a metal and conductivity?
as the number of valence electrons increases, number of delocalised electrons increases increases electrical conductivity
Why are metals good thermal conductors?
free electrons: when they gain more k.em they can move towards regions of the lattice with lower temperature and transfer heat
Which factors determine the strength of a metallic bond?
radius of cation ionic charge (they determine electron density)
Effect of radius of cation on the strength of the metallic bond:
The smaller the radius, the stronger the bond Shorter distance between the + nucleus and the delocalised electrons
Effect of charge of cation on the strength of the metallic bond:
The higher the ionic charge, the stronger the metallic bond There is a greater number of delocalised valence electrons and greater charge on the metal ion: greater charge difference results in a stronger electrostatic attraction
What is hardness?
a measure of the ability of a material to resist deformation
Relationship between strength of a metallic bond and hardness
strength of metallic bonds results in a greater hardness
Trend in melting point for s and p metals
melting point increases as metallic bond increases decreases down a group due to larger radius increases across a period due to larger charge (generally)
Where are the valence electrons in transition metals? What are the consequences of this?
they occupy both the s and d orbitals means that they have variable ionic charges
How is electron density in transition metals?
greater electron density, due to large number of valence e- from both s and d orbitals stronger metallic bond than s and p block metals
Melting point trends for transition metals
melting points are much higher for the transition elements due to the increased strength of the metallic bond
Why are transition elements harder than other metals
both 4s and 3d electrons means there is an increased attraction between these electrons and the metal ions increased strength of metallic bonds, harder
As the number of e- in d orbitals increases,
The electrostatic attraction between metal ions in the lattice and delocalised electrons increases