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.
Outline the properties of graphene
Best known electrical conductor, because it contains delocalised electrons which are free to move and carry a charge, and without layers in the structure they can move even quicker than graphite.
High melting and boiling point because of the strong covalent bonds between atoms
Transparent and light because it’s a single atom thick
What holds simple covalent structures together
Weak induced dipole dipole forces
Give and explain 2 Physical properties of simple molecular substances
Low melting point because the weak induced dipole dipole forces between the molecules need little energy to break.
Don’t conduct electricity because there are no free electrons. All the electrons are involved in bonding.
Outline the structure and properties of ice
Ice is a simple covalent structure, but has different properties to other molecules. In ice, the atoms are held together by covalent bonds.
The molecules are held together by hydrogen bonds which are the strongest intermolecular force.
In the lattice of ice, the hydrogen bonds hold the molecules further apart than in water. Here, it is described as an ‘open lattice’ structure.
When the ice melts, the hydrogen bonds break and the water molecules move closer together
Define co-ordinate/ dative bonding
The sharing of a pair of electrons where both electrons in the bond are provided by one of the bonding atoms
Draw the dot and cross diagrams for both these molecules: NH3, BF3
Draw a dot and cross diagram to show the dative covalent and covalent bonds in the following:
CO, H3O(+), NO3
Outline metallic bonding
The electrostatic forces of attraction between a lattice of positively charged ions and a sea of delocalised electrons
Explain what happens when metal atoms react together
Metallic bonding occurs:
The metal ions lose their outer shell electrons to become positively charged
The ions occupy a fixed position in the lattice
The Electrons no longer belong to any one atom but are free to move throughout the whole structure and are said to be delocalised
What type of structure do metal atoms form when they react together
Giant metallic structures
Give and explain 2 properties of metals (MP/BP, conductivity)
They have high melting points due to the strong attraction between the positive ions and negative electrons, so high temperatures are needed to break these metallic bonds
They are excellent conductors of electricity both in solid and malten states, as the delocalised electrons move freely throughout the structure and carry charge.
Which is the best conductor of electricity, Na or Al? Explain your own
Aluminium is the best conductor of electricity, as each ion has 3 delocalised electrons. In comparison, Na has only 1 delocalised electron per ion. Overall, Al had 3× more delocalised electrons to conduct electricity
Which of the metals Na or Mg has the highest melting point? Explain your answer
Mg has the highest melting point, as each ion has lost twice more electrons than ions in Na, meaning each ion has a 3× higher charge than each Na ion. This means there are much stronger electrostatic forces of attraction in Mg, which would take more heat energy to break.
What determines the shape of a molecule
The number and type of electron pairs in the outer shell surrounding the central atom
Outline the electron pair repulsion theory
As electrons are negatively charged, they repel each other.
Electrons exist in pairs- there are lone pairs (non bonding 9 and bonding pairs.
A lone pair of electrons is slightly more electron -dense than a bonded pair, so a lone pair repels more than a bonded pair.
Give the relative strengths of repulsion between different types of electron pairs, with strongest repulsion at the top and weakest at the bottom
Lone pair/ lone pair
Bonded pair/lone pair
Bonded pair/Bonded pair
Describe the shape of molecule formed that has 2 Bonding pairs and no lone pairs including the name, bond angle and drawing.
Name= Linear
Bond angle= 180°
Drawing=
Describe the shape of molecule formed that has 3 Bonding pairs and no lone pairs including the name, bond angle and drawing.
Shape= Trigonal Planar
Angle= 120°
Drawing:
Describe the shape of molecule formed that has 4 Bonding pairs and no lone pairs including the name, bond angle and drawing.
Shape: Tetrahedral
Angle: 109.5
Drawing:
Describe the shape of molecule formed that has 6 Bonding pairs and no lone pairs including the name, bond angle and drawing.
Shape: Octahedral
Angle: 90°
Drawing:
Describe the shape of molecule formed that has 3 Bonding pairs and 1 lone pair including the name, bond angle and drawing.
Name: Pyramidal
Angle: 107
Drawing
Describe the shape of molecule formed that has 2 Bonding pairs and 2 lone pairs including the name, bond angle and drawing.
Shape: Non-linear
Angle: 104.5
Drawing:
Give the name of the shape of BeCl2, the bond angle and the drawing
Shape: linear
Angle: 180
Drawing:
Give the name of the shape of BF3, the bond angle and the drawing
Name: Trigonal Planar
Angle: 120°
Give the name of the shape of NH4+ the bond angle and the drawing
Name: Tetrahedral
Angle: 109.5
Drawing:
Give the name of the shape of SF6, the bond angle and the drawing
Name: Octahedral
Angle: 90°
Drawing:
Give the name of the shape of CO2, the bond angle and the drawing and why
There are 4 bonding pairs but as these form 2 double bonds, they are classed as 2 bonding regions
Name: linear
Angle: 180
Drawing:
Give the name of the shape of NH3 the bond angle and the drawing
Name: Pyramidal
Angle: 107°
Drawing:
Give the name of the shape of H20, the bond angle and the drawing
Name: Non-linear
Angle: 104.5°
Drawing:
Describe a non polar molecule
A covalently bonded molecule in which the electrons in the bond are equally distributed between the two bonding atoms
What is a polar molecule
In covalent bonds between different atoms, one atom has a stronger attraction for the electrons than the other atom. The Electrons lie to the more electronegative end of the molecule
Is Cl-Cl polar or non polar
Non-polar
Is this molecule polar or non polar
Polar
What is formed when the electrons in a polar molecule lie closer to one of the atoms than the other
A permanent dipole
Define electronegativity
The ability of an atom to attract a bonding pair of electrons in a covalent bond
What is a permanent dipole
A small charge different across a bond, caused by the difference in the electronegativity of the bonding atoms
How does the amount of difference in electronegativity effect the polarity of a covalent bond
The greater the difference in electronegativity, the greater the permanent dipole and the more polar the covalent bond
Where on the periodic table is the most electronegative
The top right
Draw HCl, including which end is most electronegative
How can molecules with polar bonds be non polar molecules
Because if the molecule is symmetrical, the dipoles can cancel each other out
Is AlCl3 polar or non polar? Why?
Non polar, because it is a symmetrical molecule. This means that although each Al-Cl bond is polar, the dipoles cancel each other out, leading to no overall dipole
Is H20 polar or non polar? Why?
Polar, because each O-H bond is polar because of the difference in electronegativity between the O and H. The dipoles in each bond can’t cancel each other out because the molecule is unsymmetrical. This means there is an overall dipole.
What are intermolecular forces
The forces that act between molecules
Give 3 types of intermolecular force with strongest at the top and weakest at the bottom
Hydrogen bonds
Permanent dipole- dipole forces
Induced dipole-dipole forces
Explain how induced dipole-dipole forces are made
At any moment, the distribution of electrons in a molecule or atom may be uneven
This uneven distribution causes a temporary dipole to be present.
The temporary dipole in one molecule/atom induced a dipole in the neighboring molecule, because:
The less electronegative side of a dipole in one molecule/atom attracts the more electronegative side of a dipole in the neighbouring molecule to produce an induced dipole-dipole forces.
What does the strength of an induced dipole dipole interaction depend on
The number of electrons in the atom or molecule
What happens to the strength of induced dipole-dipole forces as you move down a group and why
The strength increases because the number of electrons increases
