Bonding Flashcards
Ionic bonding
Between metals and non-metals
Electrons are transferred from metal to non-metal atoms.
Positive and negative ions are formed.
Properties of ionically bonded compounds
Solid at room temperature.
High melting temperature due to giant structure.
Conduct electricity when molten or dissolved in an aqueous solution as the ions that carry the current are free to move in these states.
Brittle due to lattice of alternating charges. Contact between like charges would cause it to shatter.
Covalent bonding
Forms between a pair of non-metal atoms.
The atoms share some of their outer electrons so that each atom has a stable noble gas arrangement.
A covalent bond is a shared pair of electrons.
Atoms with covalent bonds are held together by the electrostatic attraction between the nuclei and the shared electrons
Properties of substances with a molecular (covalently bonded) structure
Low melting temperatures are due to weak attraction between molecules.
Do not conduct electricity as molecules are neutral overall, no charged particles to carry the current.
Dative covalent bonding or co-ordinate bonding
One atom with a lone pair provides both electrons in the covalent bond.
Metallic bonding
A lattice of positive ions in a sea of delocalised electrons.
Electrostatic attraction between positive ions and negatively charged sea of delocalised electrons
Giant structure
Properties of metals
Good conductors of electricity due to delocalised electrons that are free to move throughout the structure.
High thermal conductivity as the closely packed ions spread energy by vibrations.
Metals tend to be strong; strength depends on the charge on the ion (more delocalised electrons, stronger electrostatic attraction) and the size of the ion (smaller ion, closer the electrons are to the positive nucleus)
Malleable and ductile
High melting points due to giant structure and strong attraction between metal ions and delocalised electrons.
Turning a solid to a liquid/melting
Energy is required to weaken the forces between particles.
This energy is called the latent heat of melting or the enthalpy change of melting.
Temperature does not change during state change as the energy is absorbed.
Enthalpy
Heat change measured under constant pressure
Temperature
Average kinetic energy of the particles
Turning a liquid to gas/boiling
Energy is required to break all the intermolecular forces between particles.
This energy is called the latent heat of vaporisation or the enthalpy change of vaporisation.
Temperature does not change during state change as the energy is absorbed.
Crystals
Solids where particles have a regular arrangement and are held together by forces of attraction.
Strength of the forces of attraction affects the physical properties of the crystal.
Macromolecular crystals
Covalently bonded giant structure
eg diamond and graphite
Diamond
Covalent bonding
Each carbon atom forms 4 single covalent bonds with other atoms.
Giant structure
3D lattice of strong covalent bonds which is why it is very hard and has a very high melting point.
Does not conduct electricity because there are no free charged particles to carry charge.
Graphite
Covalent bonding and weaker van der Waals forces
Each carbon atom forms 3 single covalent bonds with other atoms.
Giant structure
2D hexagonal layer of covalently bonded carbon atoms. Weak van der Waals forces between layers.
P orbital contains a ‘spare’ electron that merges above and below the plane of carbon atoms
