Periodic trends in bonding and structure Flashcards
(26 cards)
How many metals are there?
92
How many non-metals are there?
22
What is the structure of metals at room temperature?
Solid - except mercury
What is the one constant property of metals?
The ability to conduct electricity
What is metallic bonding?
Strong electrostatic attraction between cations and delocalised electrons
What is the structure of a metal in metallic bonding?
The cations are in fixed positions, maintaining shape and structure
The delocalised electrons are mobile and able to move throughout the structure - carry charge
How are metal atoms held together?
By metallic bonding in a giant metallic lattice
What are the 3 key physical properties of metals?
1) Strong metallic bonds
2) High electrical conductivity
3) High melting and boiling points
What states do metals conduct electricity in?
Solid and liquid
Why do metals have good electrical conductivity?
The delocalised electrons can move through the structure, carrying charge
Why do metals have high melting and boiling points?
High temperatures are necessary to provide the large amount of energy needed to overcome the strong electrostatic attraction between the cations and delocalised electrons
Are metals soluble?
No - they don’t dissolve
What is the structure of non-metals?
Simple covalently bonded molecules
What structure do non-metals form in the solid state?
Simple molecular lattice held together by weak intermolecular forces
Which non-metals form a giant covalent lattice?
Boron, carbon, and silicon
Why do carbon and silicon form a giant covalent lattice?
They have 4 electrons in their outer shells which they use to make covalent bonds to other carbon and silicon atoms
What structure do carbon and silicon covalent bonds make?
Tetrahedral structure with bond angles of 109.5 degrees by electron pair repulsion
Are covalent bonds weak or strong?
Strong - difficult to break
What are the properties of substances with a giant covalent lattice structure?
1) High melting and boiling points
2) Insoluble
3) Non-conductors of electricity, except graphene and graphite
Why do giant covalent lattices have high melting and boiling points?
High temperatures are necessary to provide the large quantity of energy needed to break the strong covalent bonds
Why are giant covalent lattices insoluble?
Covalent bonds are too strong to be broken by interaction with solvents
Why are giant covalent lattices non-conductors of electricity?
All outer shell electrons are involved in covalent bonding so none are available for conducting electricity
Why are graphene and graphite able to conduct electricity?
One of the electrons is available for conductivity
What are the periodic trends in melting points across period 2?
Increases from group 1 to 14 (4)
Sharp decrease between group 14 (4) and 15 (5)
Melting points comparatively low from group 15 (5) to 18 (0)
