Unit 1 : Structure and bonding Flashcards
State information about covalent bonds
A covalent bond is a pair of shared electrons between two atoms. Covalent bonds are usually formed between non-metal atoms.
The atoms in a covalent bond are held together as the two positive nuclei and their common attraction for the shared pair of electrons.
State information about polar covalent bonds
Polar covalent bonds are formed when the attraction of the atoms for the pair of bonding electrons is different.
State Ionic bonds
Ionic bond is the electrostatic force of attraction between the positively and negatively charged ions.
Ions are arranged into three dimensional ionic lattice of positive and negative ions
How are ions formed?
If the difference in electronegativty values is large then the electrons within the bond transfer fro the element with lower electronegativty to te element with the higher electronegativty resulting in the formation of ions.
What states are compounds going to be at room temperature
Ionic Compounds
Covalent Network
Covalent Molecular
Ionic Compounds = Solid
Covalent Network = Solid
Covalent molecular = Liquid and gases
What is the melting and boiling point in general for these compounds
Ionic Compounds
Covalent Network
Covalent Molecular
Ionic Compounds = High Melting Points
Covalent Network = High Melting points
Covalent Molecular = Low melting points
What is the solubility for compounds
Ionic compounds and polar covalent substances are more likely be soluable in water
Non polar substances are less likely to be soluble in polar substance but will more likely be soluble in non polar solvents
Electrical Conductivity of compunds.
Metallic:
Conduction as solid - Yes
Conduction as liquid - Yes
Condution as solution - Metal do not dissolve in water
Covalent:
Conduction as solid - No
Conduction as liquid - No
Conduction as solution - No
Ionic:
Conduction as solid - No
Conduction as liquid - Yes
Conduction as solution - Yes
What are the three different types of van der waals forces
London Dispersion Forces
Permanent dipole-permanent dipole interactions.
Hydrogen Bonding
State what London dispersion forces are and give information about it
London dispersion forces are forces of attraction that can operate between all atoms and molecules. London Dispersion forces are much weaker than all other types of bonding.
London dispersion forces are formed as a result of electrostatic attraction between temporary dipoles and induced dipoles, caused by movement of electrons in atoms and molecules
The strength of London dispersion forces is related to the number of electrons within an atom or molecule
INTERMOLECULAR
State what permanent dipole - permanent dipole interactions are and give information about it
Molecules with a permanent dipole are polar.
Permanent dipole-permanent dipole interactions are additional electrostatic forces of attraction between polar molecules;
Permanent dipole-permanent dipole interactions are stronger than London dispersion forces for molecules with similar numbers of electrons.
Hydrogen Bonds
Bonding consisting of a hydrogen atom bonded to an atom of a strongly electronegative element, such as fluorine, oxygen or nitrogen, are highly polar.
Hydrogen bonds are electrostatic force of attraction between molecules that contain highly polar -OH, -NH OR H-F groups.
List the type of bonds in order of strongest starting from the strongest
Covalent Bond
Hydrogen Bonds
Permanent Dipole-Permanent Dipole interactions
London Dispersion Forces
What effect does hydrogen bonds have on boiling point, melting point, viscosity and solubility (miscibility)
Hydrogen bonds between the molecules and the water molecules makes the substance soluble and miscible with water. Both molecules are polar.
Hydrogen bonding increases the viscosity (thickness) of a substance . Hydrogen bonding brings molecules closer together and makes the substance thicker.
Hydrogen bonding elevates the melting /boiling point of a substance due to bringing the molecules closer together
Why is the boiling points of ammonia, water and hydrogen fluoride unexpectedly high
Ammonia, water and hydrogen flouride have hydrogen bonds between their molecules which raises boiling point There higher boiling points are described as anomalous as they are different from the norm.
