Physical - Bonding Flashcards
What is ionic bonding?
The electrostatic attraction between oppositely charged ions in a lattice.
What is an ionic bond?
The electrostatic attraction. The transfer of electrons has to take place first to make the ions that attract to each other, but ionic bonding doesn’t refer to this transfer.
Why can a solution of an ionic compound conduct electricity?
Because the ions are free to move.
Why can metals conduct electricity?
Because the delocalised electrons can move.
What is charge density?
charge density = charge / size
What atoms are involved in ionic bonding?
Metals and non-metals. The metal atoms lose electrons to form positive ions (cations) while the non-metal atoms gain electrons to form negative ions (anions).
What is the strength of an ionic bond?
The smaller the ions and the greater the charge on the ions, the stronger the attraction between the positive and negative ions (usually). However, once distorted, if ions of the same charge are next to each other, they repel and the structure breaks.
What is the structure of ionic compounds?
Giant, closely packed, ionic lattice structure of positive and negatively charged ions. The ions are held together by the very strong electrostatic attraction between the + and - ions. This +/- attraction is known as an ionic bond, though it is just an electrostatic attractive force.
What is the melting and boiling points of ionic compounds?
High because a lot of energy is required to overcome the strong attraction. They are solids at room temperature.
What is the conductivity of ionic compounds?
Can conduct when liquid (molten) and aqueous only because that’s when the ions are free to move. As a solid, they are fixed in place so are unable to move and carry the electric current.
Are ionic compounds soluble in water?
Generally soluble and dissolve in water.
What is covalent bonding?
The shared pair of electrons between atoms.
What is the strength of a covalent bond?
The shorter the bond, the stronger the bond (usually).
Double bonds are stronger than single bonds, while triple bonds are stronger than double bonds.
What atoms are involved in covalent bonding?
Non-metals. The atoms share electrons to obtain stable electron structures.
What structures use covalent bonding?
Simple molecular and giant covalent (macromolecular).
What are polymers?
Molecules made up of long chains of covalently bonded carbon atoms. They’re formed when lots of small molecules called monomers join together. Monomers are weaker forces and so have a lower melting and boiling point.
The more covalent bonds there are, the higher the melting point because the stronger they are and the longer it will take to break the bonds. This is because the longer chains, the more energy is required to break the bonds and cause the material to change state.
What is a lone pair?
Two non-bonded outer shell electrons.
What is a dative covalent bond? (co-ordinate)
When both the electrons come from the same species. The atom that accepts the electron pair is an atom that does not have a filled outer main level of electrons - the atom is electron-deficient. The atom that is donating the electrons has a pair of electrons that is not being used in a bond (a lone pair).
Coordinate bonds have exactly the same strength and length as ordinary covalent bonds between the same pair of atoms, but they are charged particles.
What does the arrow show in dative covalent bonds?
Shows the direction in which the electrons are donated. Once formed, dative covalent bonds are identical to other covalent bonds.
What is the structure of simple molecular elements/compounds?
Individual molecules with weak intermolecular (van der waals) forces between them. Atoms within molecules are joined by strong covalent bonds.
What is the melting and boiling points of simple molecular elements/compounds?
Low because only the weak intermolecular forces need to be broken in order to change state. Breaking the strong covalent bonds (intramolecular forces) would be a chemical rather than physical change. Most molecular substances are gases or liquids at room temperature.
What is the conductivity of simple molecular elements/compounds?
Cannot conduct because there are no charged particles that can move - simple molecular elements/compounds are neutral.
Are simple molecular elements/compounds soluble in water?
Infrequently soluble, but usually insoluble.
What is the structure of giant covalent elements/compounds?
Giant, continuous, lattice structures in which all atoms are joined to others by covalent bonds in a tetrahedral arrangement.