7.3 Periodic trends in bonding and structure Flashcards
What are semi-metals or metalloids
Elements near to the metal/non-metal divide
Cahn show in-between properties
At room temperature, all metals except mercury are…
…solids
Common property among all metals
Ability to conduct electricity
What bonding takes place in a metal
Metallic bonding
What is metallic bonding
The strong electrostatic attraction between cations and delocalised electrons
In a solid metal structure, each atom has donated its ______ outer-shell ______ to a shared pool of ______ which are ______ throughout the whole structure. The ______ left behind consist of the ______ and the inner ______ ______ of the metal atoms
Negative Electrons Electrons Delocalised Cations Nucleus Electron shells
Cations in metallic bonding
They are fixed in position, maintaining the structure and shape of the metal
Electrons in metallic bonding
The delocalised electrons are mobile and are able to move throughout the structure. Only the electrons move
In a metal structure, billions of metal atoms are held together by metallic bonding in a…
Giant metallic lattice
Most metals have:
Strong metallic bonds - attraction between positive ions and delocalised electrons
High electrical conductivity
High melting and boiling points
In what states do metals conduct electricity
Solid or Liquid
What happens when a voltage is applied across a metal
The delocalised electrons can move through the structure, carrying charge
Why can’t ionic compounds conduct electricity when solid
They have no mobile charge carriers in this state
Why is Tungsten used in the filaments of halogen lamps
It has the highest melting point, other metals would melt
What does the melting point of a metal depend on
The strength of the metallic bonds holding together the atoms in the giant metallic lattice
For most metals ______ temperatures are necessary to provide the ______ amount of energy needed to ______ the ______ ______ attraction between the cations and electrons
High
Large
Overcome
Strong Electrostatic
Why do most metals have a high melting and boiling point
The strong electrostatic attraction between the cations and electrons
Do metals dissolve
No
Many simple non-metallic molecules form a ______ ______ ______ structure and have ______ melting and boiling points due to ______ intermolecular forces
Simple Molecular Lattice
Low
Weak
What do non-metals such as boron, carbon and silicon form
A giant covalent lattice
Structure of diamond
Tetrahedral arrangement of atoms in the diamond form of carbon
Bond angles are all 109.5 by electron-pair repulsion
The dot and cross diagram shows part of covalently bonded network of carbon atoms
Melting and boiling points of substances with a giant covalent lattice structure
High melting and boiling points
Because covalent bonds are strong
High temperatures necessary to provide large quantity of energy needed to break the strong covalent bonds
Solubility of substances with a giant covalent lattice structure
Insoluble in almost all solvents
The covalent bonds holding together the atoms in the lattice are far too strong to be broken by interaction with solvents
Electrical conductivity
Giant covalent lattices are non-conductors of electricity
The only exceptions are graphene and graphite
Electrical conductivity and carbon (diamond) and silicon
All four outer shell electrons are involved in covalent bonding so none are available for conducting electricity
Why can carbon conduct electricity
Forms several structures in which one is available for conductivity. Graphene and graphite both conduct electricity
What is graphene
A single layer of graphite
Hexagonally arranged carbon atoms linked by strong covalent bonds
What is graphite
Composed of parallel layers of hexagonally arranged carbon atoms
Layers are bonded by weak London forces
Only uses three of carbon’s four outer shell electrons
Periodic trend in melting points
Across period 2 and 3,
The melting point increases from group 1 to group 14
There is a sharp decrease in melting point between Group 14 and 15
The melting points are comparatively low from group 15 to 18
