Bonding And Structure Flashcards
Define the octet rule (3 bullet points)
Atoms of elements bond together so that each atom has 8 electrons in its outer shell
Unpaired electrons pair up by sharing or transferring electrons
This results in each atom having the same configuration as a noble gas (stable)
Define ionic bonding
The electrostatic forces of attraction between oppositely charged ions
What type of elements does ionic bonding occur between
A metal and a non metal
Explain how electrons are transferred between a metal and a non metal to form an ionic bond and what this results in
Electrons are transferred from the metal (forming a positive ion) to the nonmetal (forming a negative ion). This results in both ions having the same electron configurations as the nearest noble gas
Which noble gas does the sodium ion resemble
Ne
Explain how ions are formed from atoms of metals in groups 1-3
They lose electrons to form positive ions
Explain how ions are formed from atoms of non metals in groups 5-7
They gain electrons to form negative ions
Give the formula for the ion ‘Nitrate’
Give the formula for the ion ‘Carbonate’
Give the formula for the ion ‘Sufate’
Give the formula for the ion ‘Ammonium’
Draw a dot and cross diagram to represent Magnesium Chloride
What type of structures do substances that have ionic bonding between molecules form
Giant ionic structures
Explain the structure and bonding of sodium chloride
Sodium chloride is made up of a lattice of positive ions and negative ions, held together by strong electrostatic forces of attraction (ionic bonds)
Each Na+ ion is surrounded by 6 Cl- ions
Each Cl- ion is surrounded by 6 Na+ ions
Explain why a chloride ion is bigger than a sodium ion
There are more shells in the chloride ion
Outline and explain the properties of ionic compounds
1) Solid at room temperature, with high melting and boiling points because lots of energy is needed to break the strong electrostatic forces of attraction between the oppositely charged ions
2) They can’t conduct electricity when solid but when dissolved in water or molten they are good conductors. This is because in the solid state, ions are in a fixed position in the lattice and can’t move. When molten/ dissolved in water, the ions are free to move so can conduct electricity.
Ionic compounds are soluble in polar solvents such as water because polar water molecules are attracted to the positive and negative ions in the compound. The giant ionic lattice breaks down and the Ions are surrounded by water molecules
The following table lists some of the properties of magnesium oxide:
Explain these properties in terms of the bonding and structure of Magnesium Oxide
Magnesium oxide is a giant ionic lattice formed when the Mg loses 2 electrons and the oxygen gains 2 electrons, making them oppositely charged.
This compound has a very high melting point, as there are lots of strong electrostatic forces of attraction between the oppositely charged ions, which would take a lot of heat energy to break.
This can’t conduct electricity as a solid, because the charged particles are held together in a fixed position by the electrostatic forces, however it can when molten as the ions are free to move and carry a charge.
This is also only soluble in polar solvents as the charged particles in the solvents are attracted via electrostatic forces of attraction to the oppositely charged particles in the ionic lattice. The polar molecules surround the ions, separating them and dissolving the compound.
Define covalent bonding
Covalent bonding is the strong electrostatic forces of attraction between a shared pair of electrons and the nuclei of the bonded atoms
What do you measure the strength of a covalent bond using
It is measured using average bond enthalpy.
How strong is a covalent bond with a very high average bond enthalpy
Very strong
Give 2 exceptions to the octet rule and explain them
Beryllium and Boron
They don’t have enough unpaired electrons to reach a noble gas configuration. They just pair up the unpaired electrons they do have.
Draw the dot and cross diagram for BF3
Give all the elements that can expand their octets
Group 5:
P, As
Group 6:
S, Se, Te
Group 7:
Cl, Br, I, At
Draw SF6
Give the rule from the booklet that’s ‘better than the octet rule ‘
Unpaired electrons pair up,
The maximum number of bonds that can be formed is equivalent to the number of electrons in the outer shell
What is a single covalent bond
The sharing of one pair of electrons
Draw a dot and cross diagram for the following compounds:
F2
HF
SiF4
SCl2
label any lone pairs
Give 3 examples of giant covalent structures
Diamond
Graphite
Silicon dioxide
What group tends to form giant covalent structures
Group 4
Outline the structure and properties of diamond
Each carbon atom is bonded to 4 other carbon atoms in a tetrahedral shape. The carbon atoms are held together by strong covalent bonds.
Diamond has a high melting point as a large quantity of energy is needed to break the covalent bonds
It is a poor conductor of electricity as it has no delocalised electrons, because all the electrons are involved in bonding
It is insoluble in water as the covalent bonds are too strong to be broken by either polar or non polar solvents
Outline the structure and properties of graphite
Each carbon atom is covalently bonded to 3 other carbon atoms in a trigonal shape. Graphite is a layered structure with delocalised electrons between the layers
Graphite has a high melting point as a large quantity of energy is needed to break the strong covalent bonds
It is a good conductor of electricity as the electrons between the layers are delocalised
It is insoluble in water as the covalent bonds are too strong to be broken by either polar or non polar solvents
Graphite is a lubricant as the layers of carbon atoms can slide over each other as the forces holding the layers together are weak
Outline the structure of graphene in comparison to graphite
The structure of graphene is similar to that of graphite in that each carbon atom is bonded to three other carbon atoms
However, graphene does not exist in layers and exists as a sheet of carbon atoms joined together in hexagons. Each sheet is just one atom thick.