Bonding, Structure And Properties Of Matter Flashcards
Name three types of chemical bonds
Ionic, covalent & metallic
What are the particles like in an ionic bond?
Oppositely charged ions
What do atoms do in a covalent bond to get a full outer shell?
Share pairs of electrons
What particles are involved in metallic bonding?
Positive ions and delocalised electrons
What type of bond is formed between a metal and non-metals?
Ionic bonding
What type of bonding is formed between just non-metals?
Covalent bonding
What type of bonding occurs in metals and metallic alloys?
Metallic bonding
What type of bond involves gain or loss of electrons?
Ionic
What happens when a metal and a non-metal form an ionic bond?
Electrons in the outer shell of the metal atom are transferred to the non-metal
What is the group number if an element forms a -2 ion?
6
If an atom loses two electrons to form an ion, what charge will the ion have?
2+
Loses electrons and becomes positively charged, (size of charge is the same as the number of electrons lost, aka lose 1 electron = +1, loses 2 electrons = +2)
What happens to a metal when forming an ionic bond?
Loses electrons and becomes positively charged
What happens to a non-metal when forming an ionic bond?
Gains electron and becomes negatively charged
(size of the charge is the same as the number of electrons gained, aka gain 1 electron = -1, gains 2 electrons = -2)
Why do metals and non-metals form ionic bonds?
To get a full outer shell and therefore have the electronic structure of a Noble gas.
How can the transfer of electrons when forming an ionic bond be represented?
Dot and cross diagrams.
Draw the dot and cross diagram for the formation of sodium chloride.
What are the limitations of using dot and cross diagrams to represent ionic compounds?
Does not show how the ions are arranged in space and does not show the structure in 3D.
What type of bonding is likely to occur between group 1&2 metals with group 6&7 non-metals?
Ionic.
Describe how magnesium and oxygen form an ionic bond.
Magnesium loses 2 electrons and forms a 2+ ion. Oxygen gains the 2 electrons and forms a 2- ion.
What type of force exists between oppositely charged ions?
Electrostatic.
What type of structure is found in ionic compounds?
Giant lattice.
Describe the bonding and structure in an ionic compound.
Strong electrostatic attraction between oppositely charged ions with the forces acting in all directions.
How can the structure of sodium chloride be represented? What are the limitations?
Space fill model: shows relative sizes of ions and regular pattern but can only see outer layer.
Ball & stick model: shows all the ions, bonds aren’t represented by lines, doesn’t show outer electrons.
What must the charges do when working out a formula of an ionic compound?
Cancel out.
What are the properties of ionic compounds?
High melting points/ high boiling points.
Why do ionic compounds have high melting points?
Due to the strong electrostatic attraction between oppositely charged ions which requires lots of energy to break.
Why do ionic compounds conduct when melted or dissolved in water?
Ions are free to move (can’t move when a solid!) and carry a charge.
How do you work out the empirical formula of an ionic compound from a diagram?
Work out the charges on the ions and balance them out.
A compound is made up of calcium ions and chloride ions, what is its empirical formula?
Calcium is in group 2 so forms 2+ ion, chloride is in group 7 so forms 1- ion, need 2 chlorides to balance out the charge on the calcium = CaCl2.
How are covalent bonds formed?
By sharing electrons
How many electrons does each atom donate in a single covalent bond?
1
What is the strength of a covalent bond?
Strong
What are the two types of covalent structure?
Small molecules e.g. CO2 and giant covalent (macromolecular)
How are covalent bonds represented in small molecules?
Dot & cross: Shows electrons shared
Displayed formula: Shows covalent bonds as lines or H-N—H
Space fill: Shows arrangement of atoms in 3D
What type of structure is shown in H-N-H?
Covalent structure
What are the limitations of using a displayed formula?
Does not show 3D structure
Does not show where the electrons in the covalent bond have come from
What type of bonding do you get in covalent polymers?
Covalent bonding
How are the atoms linked in a polymer?
By strong covalent bonds between the atoms and weak intermolecular forces between the polymer chains
What are the properties of small covalent molecules?
Low melting points/ boiling points (therefore gases mostly at room temperature)
Why do small covalent molecules have low boiling points?
They have weak intermolecular forces which don’t require much energy to break
What happens to the boiling point of simple covalent molecules with increasing size?
Increases because there are more of the weak intermolecular forces present
Which has the highest boiling point out of hydrogen and methane?
Methane as it is a larger molecule
So there are more intermolecular forces present, so more energy needed to break these
Why don’t simple covalent molecules conduct electricity?
Have no ions (charged particles) or delocalised electrons
Name three giant covalent structures.
Diamond, graphite and silicon dioxide (silica)
What are the melting points of giant covalent structures?
High melting point
Due to lots of strong covalent bonds.
What are the properties of diamond?
High melting point, hard, does not conduct electricity
Each C atom is bonded to 4 other atoms.
Explain the properties of diamond.
High melting point and hard due to strong covalent bonds. Does not conduct electricity as it has no free electrons or ions.
Describe the structure and bonding in diamond.
Giant covalent structure held together by lots of strong covalent bonds.
What are the properties of graphite?
High melting point, soft/slippery, conducts electricity
Each C atom is bonded to 3 other atoms.
Explain the properties of graphite.
High melting point due to strong covalent bonds. Soft/slippery because layers are held together by weak intermolecular forces. Conducts electricity due to delocalised electrons.
Why is graphite soft & slippery?
Layers are held together by weak intermolecular forces which can slide over each other.
Why does graphite conduct electricity?
Delocalised electrons are able to move through the structure and carry charge.
What is graphene?
A single layer of graphite.
What are the properties of graphene?
Strong and can conduct electricity
Due to strong covalent bonds and delocalised electrons.
What are the uses of graphene?
Electronics, nanotechnology, materials.
What are carbon nanotubes?
Sheet of graphene rolled up as a tube, cylinder shape.
What are the properties of carbon nanotubes?
Strong and can conduct electricity
Due to strong covalent bonds and delocalised electrons.
What are the uses of carbon nanotubes?
Electronics, composites, nanotechnology
Can improve strength without adding much weight.
What are fullerenes?
Molecules of carbon atoms with hollow shapes based on hexagons of carbon atoms.
What was the first fullerene discovered?
Buckminsterfullerene, which is in a spherical shape.
What are the properties of fullerenes?
Strong, can conduct electricity and thermal energy due to delocalised electrons.
What are the uses of fullerenes?
Drug delivery, catalysts (these speed up reactions), metallic bonding.
What is the structure of metallic substances?
Giant lattice.
What are the properties of metallic substances?
High melting points (most), can conduct electricity, malleable.
Describe the structure and bonding in a metal.
Giant lattice, strong electrostatic attraction between positive metal ions and delocalised electrons.
Why do metals mostly have high melting and boiling points?
Strong electrostatic attraction between positive metal ions and delocalised electrons requires lots of energy to break.
Why do metals conduct electricity?
They have delocalised electrons which are free to move through the structure and carry the current.
Why are metals malleable?
Layers of atoms can slide past each other.
Why are pure metals not suitable for many applications?
They are too soft.
What is an alloy?
A mixture of metals.
Why are alloys harder than pure metals?
Different sized atoms disrupt the layers, so layers of atoms can’t slide past each other as easily.
What are the three states of matter?
Solid, liquid, and gas.
What takes place at the melting point?
Melting and freezing.
What takes place at the boiling point?
Boiling and condensing.
How can you represent the three states of matter?
Using a simple model represented by small solid spheres.
What does the energy needed to change state depend upon?
The strength of the forces between the particles; the stronger the force, the higher the melting and boiling point.
What are the limitations of the particle model?
The model assumes no forces involved, all particles are represented as spheres, and the spheres are solid.
What are the four state symbols?
Solid (s), liquid (l), gas (g), aqueous solutions (aq) (when something is dissolved in water).
How are the particles arranged in a solid?
Tightly packed, regular arrangement, and in fixed position. Have a definite shape and volume. Can’t be compressed.
How are the particles arranged in a liquid?
Close together, disordered arrangement but free to move past each other. Able to flow, have a fixed volume, take the shape of its container. Can’t be compressed.
How are the particles arranged in a gas?
Far apart, random arrangement, no fixed volume or shape. Can be compressed.
What happens to the bonds/forces when melting?
They are weakened.
What happens to the bonds/forces when boiling?
They are broken.
What is gained during melting or boiling?
Energy.
What is the name of the process turning a liquid to a gas?
Evaporation/boiling.
What is the name of the process turning a gas to a liquid?
Condensation.
What is the name of the process turning a liquid to a solid?
Freezing.
What is the name of the process turning a solid to a liquid?
Melting.
What is nanoscience?
Structures that are 1-100 nm in size, of the order of a few hundred atoms.
What size are fine particles (PM2.5)?
Have diameters between 100 - 2500 nm.
What size are coarse particles (PM10)?
Have diameters between 1 x 10^-5 m - 2.5 x 10^-6 m. Referred to as dust.
Which particles are the smallest: nanoparticles, fine particles, or coarse particles?
Nanoparticles - they have the smallest size.
Give some uses of nanoparticles.
Many applications in medicine, electronics, cosmetics, sun creams, deodorants, catalysts, bandages, wound dressings, face masks, deodorant, socks.
Suggest a use for a nanoparticle which has antibacterial properties.
Used in bandages or wound dressings.
Give a property of a nanoparticle if it is to be used in a computer chip.
Conducts electricity.
What are the suggested possible risks of using nanoparticles in cosmetics?
Potential cell damage to the body (small enough to pass through the skin and remain in the body) and harmful effects on the environment (after being washed off the skin).
Why are catalysts in the form of nanoparticles more efficient?
They have a much higher surface area for reactions to take place.
Due to the high surface area to volume ratio.
Why do the properties of nanoparticles differ to bulk materials?
Nanoparticles have a greater surface area to volume ratio.
Suggest reasons why it costs less to use nanoparticles rather than fine particles in sun creams.
Smaller quantities are needed to be as effective as normal sized particles.
Give an advantage of using nanoparticles in sun creams than other sun creams.
Better coverage and more protection from the Sun’s ultraviolet rays.
What happens to the surface area to volume ratio when the side of a cube decreases by a factor of 10?
The surface area to volume ratio increases by a factor of 10.
How to work out surface area to volume ratio?
- Calculate the area of the cube (has 6 sides!)
- Calculate volume of the cube
- Divide area by the volume
- Write values in format surface area: volume.
Example of calculation to determine the surface area to volume ratio of a cube with sides of length 50nm.
- Area is 50 x 50 x 6 (as has 6 sides) = 15000 nm²
- Volume is 50 × 50 x 50 = 125000 nm³
- Ratio = surface area ÷ volume so is 15000 ÷ 125000 = 0.12 nm⁻¹
- 0.12: 1.
