Bonding and Structures Flashcards
Name the three types of chemical bond
Ionic, covalent, metallic
When does ionic bonding occur?
When a metallic element reacts with a non-metallic element
How does an ionic bond form?
Metal atoms lose electrons to form positive ions, they transfer these to the atoms of non-metallic elements, which form negative ions
What is an ionic bond?
An electrostatic force of attraction between oppositely charged ions
When does metallic bonding occur?
In a metallic element or alloy, between the metal ions
How does a metallic bond form?
Each ion contributes its outer electrons to a ‘sea’ of delocalised electrons, leaving behind positive ions in a lattice structure
What is a metallic bond?
An electrostatic force of attraction between the positive ions in the lattice and the negative delocalised electrons
When does covalent bonding occur?
When non-metallic atoms bond together. This can be during a reaction, or in the case of diatomic molecules, occur naturally
How does a covalent bond form?
When the outer shells of two non-metallic elements overlap each other, causing a pair outer electrons to be shared between the bonding atoms
What is a covalent bond?
The electrostatic force of attraction between the positively charged nuclei of the bonded atoms and the shared pair of electrons
Why do atoms form bonds?
To achieve a full outer shell of electrons
Describe and explain the melting and boiling properties of ionic compounds
High mp and bp because of the large amounts of energy required to break many strong bonds
Describe and explain the electrical conductivity of ionic compounds
When melted or dissolved, they conduct electricity because the ions are free to move and a charge can flow
Describe and explain the melting and boiling properties of small molecules
They only have weak forces of attraction BETWEEN the molecules, it is these that are overcome NOT the covalent bonds when the substance mealts or boils
Describe and explain the melting and boiling properties of giant covalent structures
These are solids with high melting and boiling points. All the atoms are linked by strong covalent bonds. These many bonds must be overcome to melt or boil the substance.
Explain why pure metals can be bent and shaped
The atoms are arranged in layers, which can slide over each other
Explain why alloys are much harder than pure metals
The layers are distorted because the atoms are different sizes, preventing the layers sliding over each other
Explain why metals are conductors of electricity
The delocalised electrons carry electrical charge through the metal
Explain why metals are good heat conductors
Thermal energy is tranbferred by the delocalised electrons
Describe the similarities and differences in the structures of diamond and graphite
Both made of carbon atoms
Both contain many strong covalent bonds
Diamond atoms each bond to 4 other atoms
Graphite each atoms bonds to 3 others with a sea of delocalised electrons between layers, there are no covalent bonds between the layers
