Topic 1: Atomic structure and the periodic table Flashcards
where is the nucleus found?
in the middle of the atom
what does the nucleus contain?
protons and neutrons
what is the nucleus’s charge?
positive
where are the electrons located?
around the nucleus in shells
what are the electrons charge?
-1
what are the electrons mass?
very small
what is the nucleus’s relative mass?
1
what is the protons relative mass?
1
what is an atoms overall charge?
neutral
why are atoms neutral?
because the number of protons in an atom is equal to the number of electrons
what is an ion?
an atom when the number of protons doesn’t equal the number of electrons
what does the atomic number (small one) on an atom tell you?
the number of protons
what does the mass number (big one) tell you?
the number of protons and neutrons this is the mass of the atom
how do you work out the number of neutrons in an atom?
mass number - atomic number
what decides what type of atom an atom is?
the number of protons in the nucleus
what is an element?
a substance made of one type of atom
what is an isotope?
a substance with a different number of neutrons
what is the formula for relative atomic mass?
Ar=sum of (isotope abundance x isotope mass number) / sum of abundances of all the isotopes
copper has two stable isotopes Cu 63 has a abundance of 69.2% and Cu 65 has a abundance of 30.8% calculate the relative atomic mass?
(69.2 x 63)+(30.8 x 65) / 69.2+30.8 = 63.6
what is a compound?
a substance formed of two or more elements
how are bonds made?
by electrons sharing or swapping electrons
what is ionic bonding?
when a metal and a non-metal react by swapping electrons
what is covalent bonding?
when two non-metals react by sharing electrons
what elements formed to make CO2?
1 carbon
2 oxygen
what elements formed to make Ca(OH)2
1 calcium
2 oxygen
2 hydrogen
how can you show a chemical reaction?
by writing down the products and then an –> and then the reactants eg magnesium + oxygen –> magnesium oxide
what is a symbol equation?
writing down the symbols instead of writing the equation long hand
why do you need to balance equations?
because mass cannot be gained or lost in a chemical reaction
balance the equation Fe + Cl2 –> FeCl3
2Fe + 3Cl2 –> 2FeCl3
what is a mixture?
a substance formed of atoms that are not all chemically bonded
when a compound is formed what happens to its properties?
the properties would be completely different from the individual atoms
when a mixture is formed what happens to its properties?
the mixture would have similar properties to the individual atoms properties
REQUIRED PRACTICAL: how do you use chromatography to separate dyes in ink?
1) draw a line near the bottom of a sheet of filter paper
2) add a spot of the ink to the line and pace the sheet in a beaker of solvent eg water
3) the solvent used depends on whats being tested some compounds dissolve well in waterbut sometimes stuff like ethanol is needed
4) make sure the ink isn’t touching the solvent
5) place a lid on the top to stop the solvent evaporating
6) the solvent seeps up the paper carrying the ink as well
7) each dye will move at different speeds as the dyes separate out
8) if the ink is insoluble they will stay on the baseline
9) when the solvent has nearly reached the top of the paper leave the paper to dry
10) the end pattern of spots is called a chromatogram
REQUIRED PRACTICAL:how to separate using evaporation?
1) pour the solution into an evaporating dish
2) slowly heat the solution the solvent will evaporate and the solution will get more concentrated eventually crystals will start to form
3) keep heating the evaporating dish until all you have left are dry crystals
REQUIRED PRACTICAL:how to separate using crystallization?
pour the solution into an evaporating dish and gently heat the solution some of the solvent will evaporate and the solution will get more concentrated
2) once some of the solvent has evaporated or when you see crystals start to form remove the dish from the heat and leave the solution to cool
3) the salt should start to form crystals as it becomes insoluble in cold highly concentrated solution
4) filter the crystals out of the solution and leave them in a warm place to dry you could also use a drying oven or a desiccator
REQUIRED PRACTICAL:how to separate rock salt using filtration and crystallization?
1) grind the mixture to make sure the salt crystals are small so will dissolve easily
2) put the mixture in the water and stir the salt will dissolve but the sand wont
3) filter the mixture the grains of sand wont fit through the tiny holes in the filter paper so they collect on the paper instead the sale passes through the filter paper as it is part of the solution
4) evaporate the water from the salt so that it forms dry crystals
REQUIRED PRACTICAL:how to separate using simple distillation?
1) it is used to separate out a liquid from a solution
2) the solution is heated the part of the solution that has the the lowest boiling point evaporates first
3) the vapor is then cooled , condenses (turns back to the liquid) and is collected
4) the rest of the solution is left behind in the flask
5) you can use simple distillation to get pure water from sea water the water evaporated and condensed and collected eventually you will end up with just the salt
6) the problem with simple distillation is that you can use it to separate things with very different boiling points - if the temperature goes higher than the boiling point of the substance with the higher boiling point they will mix again
7) if you have a mixture of liquids with similar boiling points you need another method to separate them - like fractional disstilation
REQUIRED PRACTICAL:how to separate using fractional distillation?
1) if you have a mixture of liquids you can separate it using fractional distillation here is a lab demonstration that can be used to model fractional distillation of crude oil at a refinery
2) you put your mixture in a flask and stick a fractional column on top then you heat it
3) the different liquids will have a different boiling points so they will evaporate at different temperatures
4) the liquid with the lowest boiling point evaporates first when the temperature on the thermometer matches the boiling point of this liquid it will reach top column
5) liquids with higher boiling points might also start to evaporate but the column is cooler towards the top so they will only get part of the way up before condensing and running back down towards the flask
6) when the first liquid has been collected you raise the temperature until the next one reaches the top