Flashcards in module 2 Deck (76):
What is a stable electronic structure?
A atom with a full outer shell.
How do metals and non-metals form ions?
metals-lose electrons to get full outer shell, non-metal-gain electron to gain full outer shell.
What do all atoms in the same group have in common?
Same amount of electrons on outer shell.
What is the sequence for each group gaining or losing electrons to become charged from group 1-7?
How does ionic bonding work?
When metal and non-metal react together, metal loses electron to become positively charged ion, non-metal gains these to form negative ion. Oppositely charged ion strongly attracted to one another by electrostatic forces, attraction called an ionic bond.
How would the formation of sodium oxide be shown on a dot and cross diagram?
To dots from outer shell of 2 sodium atoms transfer their electrons to outer shell of 1 oxygen atom. Making end result [Na]+ [O]2-[Na]+ + and 2- are small at top right. Look at revision guide for full diagram.
What are the positives and negatives of the dot and cross diagrams?
Positives: showing how ionic compounds are formed.
Negatives: Don't show structure, size of ions or how they are arranged.
What is the structure of ionic compounds called
Giant ionic lattice
How are ions formed in ionic compounds?
closely packed in regular lattice arrangement, strong electrostatic forces of attraction between oppositely charged ions, in all directions in the lattice.
How would a sodium chloride ionic compound look?
held in 1 giant ionic lattice. Na+ and Cl- are held together in regular lattice.
What are the properties of ionic compounds?
high melting and boiling points due to many strong bonds between ions. Takes a lot of energy to overcome this attraction.
Can ionic compounds conduct electricity and why?
When solid, ions held in place so compound can't conduct electricity. When compound melt ions are free to move and they'll carry electric current.
What happens when ionic compound dissolve in water?
Ions separate and are all free to move in solution, so they'll carry electric current.
What should a diagram of an ionic compound look?
Might have to work out empirical formula of compound from diagram of compound. Dot and cross diagram. Count how many atoms there are of each element. Write down to give empirical formula.
How should you do with the 3D diagram of ionic compound?
use it to work out what ions in ionic compound balance charges of ions so overall charge on compound is zero.
How do covalent bonds form?
non-metals bond together, share pairs of electrons to make covalent bond. Positively charged nuclei of bonded atoms are attracted to shared pair of electrons by electrostatic forces, making covalent bonds very strong, only share electrons on outer shell (highest energy levels).
What does an extra electron mean to the atoms?
Each atom involved generally makes enough covalent bonds to fill up outer shell. Full outer shell gives them the electronic structure of noble gas, which is very stable.
When do covalent compounds happen?
compounds of non-metals e.g. H2O an non-metal elements e.g. Cl2.
How is the dot and cross diagram useful for covalent bonds and what are the positives and negatives of them?
Electrons drawn in overlap (see revision guide) between the outer orbitals of 2 atoms are shared between atoms. Dot and cross diagrams useful to show which atoms the electrons in a covalent bond come from, but don't show relative sizes of atoms or how atoms are arranged.
What are the positives and negatives of displayed formula and 3D model?
Shows how atoms connected in large molecule. Don't show 3D structure of molecule, or which atoms electrons in covalent bond come from. 3D model quickly get confusing for large molecules. where there are lots of atoms. Don't show where electrons in bond come from.
How can you find molecular formula of a simple molecular compound?
By counting how many atoms of each element there are.
How are simple covalent bonds joined?
few atoms joined by covalent bonds.
What is in the overlap of a covalent bond called depending on the amount of electrons?
If 2 electrons in overlap-called single covalent bond. If 4 in overlap called double covalent bond. If 6-triple bond.
What bonds are within simple covalent structures and what needs to be done to melt or boil them?
very strong molecules. Forces of attraction between molecules are very weak. To melt or boil molecule need to break feeble intermolecular forces and not covalent bonds. Melting and boiling points are very low because molecules are easily parted from each other.
What are properties of simple molecular structures and covalent bonds?
Usually gas or liquid at room temperature, as molecule gets bigger strength of intermolecular force increase, so more energy needed to break them, melting and boiling points increase. Molecular compounds don't conduct electricity. because aren't charged; so no free electrons or ions.
What is a polymer and what joins the atoms together?
lots of small units linked together to form long molecule that has repeating sections. Joined together by covalent bonds.
What should a diagram of polymers look?
can draw shortest repeating section in brackets and put a small n on the bottom right to show it repeats. To find molecular formula write down molecular formula of repeated section an put 'n' outside bracket. e.g. poly(ethene)=(C2H4).
What are the properties of polymers?
Larger than intermolecular forces than simple covalent molecules, more energy needed to brake them. Most polymers are solid at room temperature. Intermolecular forces still weaker than ionic or covalent bonds so generally have lower boiling points than ionic or giant molecular compounds.
What forces bond giant covalent structures and what are their properties?
Bonded by strong covalent bonds, high melting and boiling points so lots of energy needed to brake covalent bonds between atoms. Don't contain charged particles-don't conduct electricity-not even when molten (few exceptions e.g. graphite).
What is diamond? for diagram see revision guide.
giant covalent structure, each carbon atom forms 4 strong covalent bonds making diamond really hard and needs lots of energy to break-high melting point, in a very rigid giant covalent structure. Doesn't conduct electricity because has no free electrons or ions.
What is the giant covalent structure graphite? for diagram see revision guide.
Each carbon atom forms 3 covalent bonds to create layers of carbon hexagons. Each carbon atom also has one delocalised electron. No covalent bonds between layers-held together weakly-free to move over each other. Makes graphite soft and slippery making graphite the ideal lubricating material. High melting point-covalent bonds need lots of energy to break. Only 3 of 4 electrons in outer shell shared-1 delocalised electron-conducts electricity and thermal energy.
What is the giant covalent structure silicon dioxide? For diagram see revision guide
Sometimes called silica, this is what sand is made of. Each grain of sand is one giant structure of silicon and oxygen
What is graphene?
sheet of carbon joined in hexagons. Sheet 1 atom thick-2 dimensional compound. Network of covalent bonds makes it very strong, incredibly light-can be added to composite materials to improve strength without adding much weight. Contains delocalised electrons so can conduct electricity through whole structure. Means has potential to be used in electronics.
What are fullerenes?
molecules of carbon shaped like closed tube or hollow balls. Mainly made of carbon atoms arranged in hexagons but also contain pentagons or heptagons.
What can fullerenes be used in?
can be used to 'cage' other molecules. Fullerene structure forms around another atom or molecule, then trapped inside. Could deliver drug into body. Has high surface area, could help make great industrial catalysts-individual catalyst molecule could be attached. Also make great lubricant.
What are nanotubes?
What fullerenes come from-tiny carbon cylinders. Ratio between length and diameter of nanotubes is high, can conduct electricity and thermal energy (heat). Have high tensile strength (don't break when they're stretched)
What are uses of nanotubes
Technology that uses small particles such as nanotubes is called nanotechnology. Nanotubes can be used in electronics or to strengthen materials without adding much weight such as tennis racket frames.
How can metals conduct electricity?
metals are giant structure. Electrons in outer shell of metal atoms are delocalised. Strong forces of electrostatic attraction between positive metal ions and shared negative electrons.
What forces act on metals?
forces of attraction hold atoms together in regular structure and are known as metallic bonding. Metallic bonding is very strong.
How are metals/metallic elements/alloys held in metallic bonding?
Delocalised electrons in metallic bonds which produce all the properties of metals.
What are the results of metals being solid at room temperature?
electrostatic forces between metal atoms and delocalised sea of electrons are very strong (revision guide). So needs lots of energy to be broken. Most compounds with metallic bonds have very high melting and boiling points, so generally solid at room temperature.
Why are metals good conductors of electricity and heat?
Delocalised electrons carry electrical current and thermal (heat) energy through whole structure, so metals are good conductors of electricity and heat.
Why are most metals malleable?
Layer of atoms in metal can slide over each other, making metal malleable-means they can be bent or hammered or rolled into flat sheets.
Why do some metals need alloys to make them stronger?
pure metals are often soft, so are mixed with other metals to make them harder, most of metals we use everyday are alloys-mixture of 2 or more metals or metal and other element. Alloy is harder and more useful than pure metals.
Why are different sized alloys used for different metals?
When new element is mixed with pure metal, new metal atoms will distort layers of metal atoms, making it more difficult for them to slide over each other. Makes alloys harder than pure metals.
What controls what state a material is at?
temperature depends on how strong the forces of attraction are between particle and material.
What are the 3 things forces depend on?
material, temperature, pressure.
How do particles behave in solids?
strong forces of attraction between particles, which holds them closer together in fixed positions to form a very regular lattice arrangement. Particles don't move from their positions, so all keep a definite shape and volume and don't flow. Particle vibrate about their positions-hotter the solid becomes, more they vibrate (causing solids to expand slightly when heated.)
How do particles behave in liquid?
Weak forces of attraction between particles. Random arranged and free to move past each other, tend to stick closely together. Have definite volume but don't keep definite shape and flow to fill bottom of container.
How do particles behave in gases?
Very weak forces of attraction, free to move and far apart. Particles in gases travel in straight lines. Gases don't keep definite shape or volume, will always fit container. Particles move constantly with random motion. Hotter gas gets faster move. Gases either expand when heated or their pressure increases.
What are the negatives of the particle model?
particles aren't solid or inelastic and aren't spheres-they're atoms, ions or molecules. Also model doesn't show forces between particles so there's no way of knowing how strong they are.
What is aqueous?
Dissolved in water (see revision guide to see state symbols).
What is the first stage of physical change?
When solid is heated its particles gain more energy
What is the second stage of physical change?
Makes particles vibrate more, which weakens forces that hold the solid together.
What is the third stage of physical change?
At certain temperature, called melting pint particles have enough energy to break free from their positions. Called melting and solids turns into liquid
What is the fourth stage of physical change?
When liquid is heated again, particles get even more energy
What is the fifth stage of physical change?
Energy makes particles move faster, weakens and brakes bonds holding liquid together
What is the sixth stage of physical change?
At certain temperature called boiling point, particles have enough energy to break bonds. This is boiling (or evaporating) liquid becomes gas
What is the seventh stage of physical change?
As gas cools, particles no longer have enough energy to overcome forces of attraction between them.
What is the eighth stage of physical change?
Bonds form between particles
What is the ninth stage of physical change?
At boiling point, so many bonds have formed between gas particles that gas becomes liquid. Called condensing.
What is the tenth stage of physical change?
When liquid cools, particles have less energy, so move around less
What is the eleventh stage of physical change?
There's not enough energy to overcome attraction between particles, so more bonds form between them.
What is the twelfth stage of physical change?
At melting point, so many bonds have formed between particles that they're held in place. Liquid becomes solid, called freezing.
What does energy depend on in physical change?
the strength of forces between particles are, stronger forces=more energy needed to brake them=higher melting and boiling points.
What are coarse particles?
(PM10[small 10]) and 10,000 nm (1*10-5m). Also called dust.
What are fine particles?
(PM2,5[small 2.5]) has diameter 100nm (1*10-7m) and 2,500nm (2.5*10-6m)
What are nanoparticles?
has diameter between 1nm (1*10-9m) and 100nm (1*10-7m). Particles contain only a few hundred atoms.
What is the area of science around nanoparticles?
What is the equation for surface area to volume ratio?
surface area to volume ratio=surface area/volume.
What happens as particles decrease in size to their surface area?
Surface area increases in relation to their volume. Causes their surface area to volume ratio to increase.
What is the surface area of nanoparticles?
have high surface area to volume ratio, means surface area is very large compared to volume.
What does surface area to volume ratio of nanoparticles have an effect on material?
Can cause properties of material to be different depending on whether it's a nanoparticle or a bulk. E.g. you'll often need less of a material that's made up of nanoparticles to work as an effective catalyst compared to a material; made of 'normal' size particles (containing billions of atoms rather than a few hundred)
What are the uses of nanoparticles?
high surface area to volume ratio-new catalysts. Nonomedicine-tiny particles are absorbed more easily by body than most particles. Can deliver drugs to cells where needed. Some nanoparticles conduct electricity-used in tiny electric circuits for computer chips, silver nanoparticles have antibacterial properties-added to polymer fibers that are often used in surgical masks and wound dressing and can also be added to deodorants. Nanoparticles also being used in cosmetics. E.g. used to improve moisturisers without making them really oily
What are the negative sides to nanoparticles?
Way affect body not fully understood-important to test new products thoroughly to minimise risks. Some worried that products containing nanoparticles been available before effects on human health been investigated properly, we don't know long-term impacts on health. Some believe products containing nanoscale products should be labelled, so customers can choose whether or not to use them.