Flashcards in module 1 Deck (72):
What is the radius of an atom
What is the radius of a nucleus?
1*10 to power of -14, almost all mas is concentrated in postivly charged nucleus.
What do electrons move in?
Electron shell, cover a lot of space mass is 1/2000, often taken as 0.
What happens in an ion?
Number of protons doesn't equal number of electrons, has overall charge.
What does the atomic number tell you?
Number of protons, mass number total amount of protons and neutrons. To get neutrons subtract atomic number from mass number.
What decides the type of atom?
Protons. e.g. 1 proton=hydrogen 2=helium.
What happens if a substance only contains atoms with the same number of protons called?
Element, only 100 elements.
What do different elements have in common?
Same number of protons.
What is an isotope?
different forms of same element, have same number of protons but different number of neutrons. (same atomic number but different mass number)
What happens because many elements exist as a number of different isotopes?
Relative atomic mass is used instead of mass number when referring to the element as whole. Average mass taking into account the different masses and abundances (amounts) of all isotopes that make up element.
What is the formula to work out relative atomic mass?
relative atomic mass (Ar[small r])=sum of (isotope abundance * isotope mass number)/sum of abundance of all isotopes.
How do compounds form?
Elements react, atoms combine with other atoms to form compounds, compounds are substances formed from 2 or more elements, atom of each are in fixed proportions throughout compound and they're held together by chemical bonds.
How do you make bonds?
atoms giving away, taking or sharing elements of compound out again, chemical reaction is needed to do this. Compound formed from metal and non-metal consists of ions. Metal atoms lose electrons to become positively charged and non-metals gain to for negative ions. Opposite charges of ions mean they're strongly attracted to each other. Called ionic bonding. E.g. sodium chloride, magnesium oxide and calcium oxide.
How do compounds form from molecules?
Form from non-metals. Each atom shares an electron with another atom, called covalent bonding. E.g. hydrogen chloride gas, carbon monoxide and water.
What are the properties of compounds?
different from original element E.g. if iron (lustrous magnetic metal) and sulfur (nice yellow powder) react, compound formed (iron sulfide) a dull grey solid lump doesn't behave anything like either iron or sulfur.
When are brackets used in formula of compounds?
E.g. Ca(OH)2 [small at bottom]. Little number outside bracket applies to everything inside bracket. So in example there's 1 calcium atom, 2 oxygen atom and 2 hydrogen atoms.
What are the examples of compound formulas?
Ammonia-NH3 sodium chloride NaCl carbon monoxide- CO hydrochloric acid-HCL, calcium chloride-CaCl2, sodium carbonate-Na2Co3, sulfuric acid-H2SO4.
How do you balance an equation?
Only change number in front of substance not in front of it.
How are mixtures created?
No chemical reaction, mixture is either elements or compounds. Can be separated out by physical change e.g. filtration, crystallisation, simple distillation, fractional distillation and chromatography.
What are examples of mixtures?
air, crude oil etc. Properties of mixtures are just properties of separate parts-chemical properties of substance aren't affected by it being part of mixture. Mixture will contain properties of its elements it is made of.
What are the first few steps for chromatography?
Draw line near bottom of sheet of filter paper use pencil. Pencil marks are insoluble and won't dissolve in solvent. Add spot of ink to line and place sheet in beaker of solvent. Solvent used depends on what being tested. Some compounds dissolve well in water, sometimes other solvents, like ethanol are needed.
What do you do after the solvent is added in chromatography?
Make sure ink isn't touching solvent-don't want it to dissolve into it. Place lid on top of container to stop solvent evaporating, solvent seeps up paper carrying ink with it. Each different dye in ink will move up paper at different rate so dyes spread out. Each dye will form spot in different place-1 spot per dye in ink.
What are the final steps of chromatography?
If any dye in ink are insoluble in solvent you've used, they'll stay on baseline, when solvent has nearly reached top of paper, take paper out of beaker and leave it to dry, end result is pattern of spots called a chromatogram.
What is filtration?
used in product is insoluble solid that needs to be separated from liquid reaction mixture. Can be used in purification as well. E.g. solid impurities in reaction mixture can be separated out using filtration.
What is evaporation?
Pour solution in to evaporating dish, slowly heat solution. Solvent will evaporate and solution will get more concentrated. Eventually crystals will start to form. Keep heating evaporating dish until all you have left are dry crystals.
What is crystallisation?
Pour solution into evaporating dish and gently heat solution. Some of solvent will evaporate and solution will get more concentrated. Once some of solvent has evaporated or when you see crystals start to form (point of crystallisation), remove dish from heat and leave solution to cool. Salt should start to form crystals as it becomes insoluble in cold, highly concentrated solution, filter crystals out of solution and leave them in warm place to dry. Could also use drying oven or desiccator.
What is the mixture rock salt?
Rock salt is mixture of rock and sand (spread on roads in winter). Salt and sands are both compounds-but salt dissolves in water sand doesn't. Vital difference in physical properties gives great way to separate them.
How do you separate rock salt?
Grind mixture to make sure salt crystals are small so will dissolve easily. put mixture in water and stir. Salt will dissolve but sand won't. Filter mixture. Grains of sand won't fit through tiny holes in filter paper, so collect on paper instead. Salt passes through filter paper as it's part of solution Evaporate water from salt that it forms dry crystals.
What is simple distillation?
used to separate out liquid from solution. Solution is heated. Part of solution that has lowest boiling point evaporates first. Vapour is then cooled, condenses (turns back into liquid) and is collected. Rest of solution is left behind in flask.
What are the steps of simple distillation after the solution has been left behind in a flask?
Can use simple distillation to get pure water from seawater. Water evaporates and is condensed and collected. Eventually you'll end up with just the salt left in flask. Problem with simple distillation is you can only use it to separate things with very different boiling points. If temperature goes higher than boiling point they will mix again.
What happens if you have a mixture of liquids with similar boiling points in simple distillation?
You need another to separate them-like fractional distillation.
What is fractional distillation?
If have mixture of liquids you can separate using fractional distillation.
How is fractional distillation used to separate crude oil at a refinery?
Put mixture in flask and stick fractionating column on top. Then heat it. Different liquids will all have different boiling points-so will evaporate at different temperatures. Liquid with lowest boiling point evaporates first. When temperature on thermometer matches boiling point of liquid will reach top of column.
What are the final steps of fractional distillation?
Liquids with higher boiling points might also start to evaporate. But column is cooler towards top. So they only get part of the way up before condensing and running back down towards the flask. When fist liquid has been collected, you raise temperature until next one reaches top.
What did J.J. Thomson discover?
electrons, these could be removed from charge. Dalton's theory wasn't quite right. Thomson suggested atoms were spheres of positive charge with tiny negative electrons stuck in them-plum pudding model. His measurements of charge and mas showed atom contained small electrons.
What did John Dalton Dalton and Democritus agree on?
matter was made up of tiny spheres (atoms) that couldn't be broken up, be Dalton thought each element was made from different types of atoms.
What was the plum pudding model?
Showed atom as ball of positive charge with electrons stuck in it.
What did Rutherford discover?
he fired alpha particles at thin gold foil-alpha scattering experiment. From plum pudding model expected them all to go through sheet or slightly deflected. Most went through some more deflected more than expected, few deflected back the way they came. Plum pudding model proved wrong.
How did Rutherford's experiment change the shape of the atom?
due to some alpha particles coming back scientist knew most mass of atom was concentrated in centre in tiny nucleus. Nucleus had positive charge since repelled positive alpha particles. Because nearly all went through most of atom was empty space-first nuclear atom
How did the atom look after Rutherford?
The nuclear model that resulted from alpha particle scattering experiment was a positively charged nucleus surrounded by cloud of negative electrons.
What did Niels Bohr discover?
electrons orbiting nucleus do it in certain distances called energy levels in fixed shells and aren't anywhere in between and distances form nucleus. His theoretical calculations agreed with experimental data. After Bohr further experiments found protons subatomic particle to make the nucleus positively charged.
What did James Chadwick discover?
proved existence of neutron explained imbalance between atomic and mass numbers. and had charge of hydrogen nucleus.
What does the current model of an atom look like?
the nucleus' radius is 10,000 times smaller than the atom. radius of atom is 1*10 to the power of -10 m. if electrons gain energy by absorbing EM radiation have to move to higher energy level far from nucleus (opposite with other way round).
What are the lowest energy levels at?
Always filled first-closest to nucleus. 1st shell 2 2nd shell 8, 3rd shell 8.
When could we first find the atomic numbers of elements?
20th century when protons and electrons were discovered.
What was a periodic pattern?
Relative atomic mass groups. Done in periodic pattern was noticed in properties. Where 'periodic table' comes from. Some elements were grouped in wrong ways in the old arrangement because it only took into account mass not other properties.
What did Dmitri Mendeleev discover in 1869?
Took 50 elements and arranged them into his own table of elements which overcame some of the earlier problems. Put them mainly in atomic mass but did switch order if properties meant it should be changed. e.g. I has a small mass but is placed after Te as it has similar properties to elements in the group.
Why were gaps left?
To fill in elements in the future with similar properties. Could predict the properties. When they were found they were filled in the pattern help confirm Mendeleev's ideas. He made good predictions about physical and chemical properties of element called ekasilicon now called germanium.
How did the discovery of isotopes help confirm Mendeleev ideas to not put elements in a strict order of atomic mass but to also take into account their properties?
Isotopes of same element have different atomic masses but have the same chemical properties so occupy same position on periodic table.
How are elements laid ?out in the periodic table
increasing atomic number in repeating patterns in properties occur periodically. elements with similar properties form columns (vertical columns called groups). Group tells you how many electrons on outer shell. reactions depend on electrons on outer shell.
Where are metals and non-metals found on the periodic table?
non-metals on right, metals on left.
How can you make predictions in reactions in periodic table?
e.g. group 1 reactivity decreases as go down. rows called periods. New period represents new outer shell.
What are properties of metals and non-metals in periodic table?
form positive ions, towards bottom left of table, most elements in table are metals, non-metals at far right and top of periodic table, non-metals don't generally form positive ions when react.
How does the electronic structure of atoms affect how they react?
Atoms generally react to make full outer shell, via losing, gaining or sharing electrons, metals to left of table don't have may electrons to remove, metals to bottom of table have outer shell electrons which are long way from nucleus do feel weaker attraction. Both effects mean not much energy is needed to remove electrons so is feasible for elements to react to form positive ions with full outer shell.
How does the electronic structure of non-metals affect how they react?
non-metals find harder to form positive ions. to right of table have lots of electrons to remove to get full outer shell, or towards top, where outer electrons are close to nucleus so feel strong attraction. Far more feasible for them to either share or gain electrons to get full outer shell.
What are properties of metals and non-metals?
metals:strong, can be bent or hammered into different shape (malleable), high boiling points. We know the rest, non-metals:no metallic bonding don't tend to exhibit same properties as metals. Tend to be dull looking more brittle aren't always solid at room temperature, don't generally conduct electricity and often have lower density.
What are properties of transition metals?
centre of table, typical metals can have more than 1 ion, often coloured so compounds contain them of colourful, good catalysts
What are properties on group 1 metals?
have 1 electron on outer shell-reactive and similar properties, often soft and low density. Increasing reactivity as you go down, more easily lost as attraction between nucleus and electron decreases-electron further away from nucleus further down group, low melting and boiling points, higher relative atomic mass.
How does group 1 metals react?
don't need much energy to react to form outer shell, easy for them to lose outer electron that they only ever react from ionic compounds. Compounds are generally white solids that dissolve in water to form colourless solutions.
How do alkali metals react in water?
react vigorously to produce hydrogen gas and metal hydroxides-salts that dissolve in water to produce alkaline solutions. More reactive lower down group-more violent in reaction, amount of energy given out by reaction increases down group-reaction with potassium releases enough energy to ignite hydrogen.
How do group 1 metals react with chlorine?
react vigorously when heated in chlorine gas to form white metal chlorine salts, as go down group reactivity increases so reaction with chlorine gas gets more vigorous.
How do group 1 metals react in oxygen?
react with oxygen to form metal oxide.
What are properties of transition metals?
group 1 more reactive than transition metals-react more vigorously with water, oxygen or group 7 elements. Also much less dense, strong and hard than transition metals, and have much lower melting pints. e.g. manganese melts at 2000 degrees, sodium melts at 98 degrees.
What are properties of group 7 elements?
colourful, as go down group become less reactive-harder to gain extra electron, because outer shell's further down nucleus, higher melting and boiling point, have higher relative atomic mass. All in group react in similar way because 7 electrons in outer shell.
What are halogens?
Form 1-ions called halides, from called ionic structures
How do more reactive halogens displace less reactive ones?
Displacement reaction occurs between more reactive halogen and salt of less reactive one. e.g. chlorine can displace bromine and iodine from an aqueous solution, of its salt (bromide or iodide). Bromine will also displace iodine because of trend in reactivity.
What are properties of group 0 elements?
have 8 electrons in outer shell, apart from helium which has 2. Don't give up or gain electrons to become more stable. Means more or less inert-don't react much at all. Exist as monatomic gases-single atoms not bonded to each other, all elements in group 0 are colourless gases at room temperature, not flammable.
What are patterns in properties of noble gases?
Boiling points of noble gases increases as go down group along with increasing relative atomic mass.
What does an increase in boiling point mean?
Increase in boiling points is due to increase in number of electrons in each atom leading to greater intermolecular forces between them which need to overcome. More intermolecular forces for small molecules.
What are the elements in group 0 starting from top?
Helium, neon, argon, krypton, xenon, radon.
What are elements in group 7 starting from top?
Fluorine, chlorine, bromine, iodine, astatine