The atom, symbols, relative atomic mass, electronic charge and isotopes Flashcards
Define an element
A substance made up of only one type of atom
Define a compound
A substance made up of atoms from two or more different elements which have been chemically bonded together
Define a mixture
A mixture is made up of two or more elements that are not chemically bonded together
(so the poperties of the substanes in the mixture remain unchanged)
Name some physical processes by which mixtures can be separated
Filtration
Crystalisation
Simple or Fractional Distillation
Chromatography
*simple and fractional distillation are two different types
What is a solvent?
A liquid in which a substance (solute) is dissolved
think: solvent= the liquid where the solute dissolves
What is a solute?
A substance that will be dissolved into a liquid
What is a solution?
The result of when a soluble solute is dissolved in a solvent.
What is the solute called when it does not dissolve into the solvent?
Insoluble solute
What is the solute called when it does dissolve into the solvent
Soluble solute
What is an insoluble solute with a solvent called?
A mixture
What is a soluble solute with a solvent called?
A solution
What does filtration do?
Separates insoluble solutes from a solvent
Describe the process of filtration
- Take a funell and place some filter paper inside and place this ontop of a beaker
- Pour the mixture through the funnel and filter paper
- The solvent should filter through into the beaker, the insoluble solvent will be left behind on the filter paper as residue
What does Crystalisation do?
Separates soluble solutes from a solution
Describe the process of Crystalisation
- Pour the solution into an evaporation dish
- Prepare a water bath and place the evaporating dish in the bath so that the solution can be heated gently
- Now some of the solvent willstart to evaporate and we will start to see crystals forming
- Stop heating the solution and store the dish in a cooler place. More crystalswill start to form because solids are less soluble in colder temperatures
- Now filter out these crystals using filter paper and a funnel, then dry out the crystals by leaving them somewhere warm
What is simple distillation?
Using the specific boiling points to separate a solvent from a solution
Describe the process of simple distillation
- Using a bunsen burner heat up the solution in the flask
- This will lead the desired solvent to evaporate
- As it rises to the top of the flask, the pressure will force it down the condenser
- The gas will cool and condense back into a liquid
- This liquid will run down the pipe and be collected in a beaker, after continuous heating, all thatwill be left in the flask is the solute.
What is fractional distillation?
Using specific boiling points to separate a mixture of liquids
What is paper chromatography
A technique used to separate different substances in a mixture
-paper chromatography separates different dyes in an ink
Describe the process of paper chromatography
- Take a piece of chromatography paper (the stationary phase) and use a pencil to draw the baseline at the bottom of the sheet
- Add your sample of ink to the pencil line
- Pour a shallow amount of solvent (e.g water or ethanol) into a beaker
- Place the filter paper into the beaker, making sure that you don’t submerge the** pencil line** and the spot of ink
- Place a** lid** ontop of the beaker to stop the solvent from evaporating
- The** solvent ** is the mobile phase. It will ** seep** up the paper, and the different dyes within the ink will dissolve in the solvent and move up with it.
- The dye that is more soluble will be more attracted to the mobile phase (the solvent) and travel further up the paper than a substance that is less soluble and more attracted to the stationary phase (the paper). They will end up separating out
- Take the paper out of the beaker and leave it to dry. This forms a chromatogram
What is the mobile phase in chromatography?
The solvent (e.g water or ethanol) in which the molecules can move in
hence it is mobile
What is the stationary phase in chromatography?
The substance or material that the molecules can’t move in
(e.g. a solid like paper or a really thick liquid)
hence it’s the stationary phase
Why do we draw the baseline in pencil?
If we drew the line in pen, the pen ink could dissolve in the solvent and move up the paper. Pencil will not do this.
What were atoms originally thought to be?
Tiny spheres that could not be divided
What did Rutherford’s Goild Foil Experiment Consist of?
Rutherford fired positively charged alpha particles at a sheet of gold foil which was surrounded by a flourescent detector which would flash when hit by alpha partciles
What were the results of the Rutherford Gold Foil Experiment?
Some of the particles bounced back
Some of the particles were deflected at large angles
Some of the particles went through the foil.
What conclusions did Rutherford come up with as a result of the Gold Foil Experiment?
As** some of the particles went through**, he concluded that the atom consists of mostly empty space
As some of the particles bounced back, he concluded that there was a very dense centre where the mass of an atom was concentrated (the nucleus)
As some of the particles deflected at large angles, he concluded that the nucleus was positively charged, as the alpha particles he fired at the sheet were positively charged and like charges repel eachother.
Who created the plum pudding model of the atom?
J.J Thompson
What is the plum pudding model?
The plum pudding model suggested that the atom was a ball of positive charge with negative electrons embedded in it
Name four differences between the plum pudding model and the nuclear model
- The nuclear model is mostly empty space, where as the plum pudding model is solid
- The positive charge of the nuclear model is all in the nucleus, in the plum pudding model the whole atom is a ball of positive mass
- The mass of the nuclear model is concentrated in the nucleus, in the plum puddingmodel, the mass is distributed throughout
- In the nuclear model, the electrons orbit the nucleus, in the plum pudding model, the electrons are embedded
Who discovered the electron shells?
Niels Bohr suggested that electrons orbit the nucleus at fixed distances
What is the equation for relative atomic mass?
sum of (isotope abundance x isotope mass numbers)/100
What is the relative mass of a proton?
1
What is the relative charge of a proton?
+1
What is the relative mass of a neutron?
1
What is the relative charge of a neutron?
0
What is the relative mass of an electron?
Very small
What is the relative charge of an electron?
-1
In an atom, the number of electrons is equal to the number of what?
Protons
What is the overall charge of an atom
0
Why do atoms have an overall charge of 0?
Atoms have an equal number of protons and electrons. Protons are positively charged and electrons are negatively charged so they cancel eachother out.
In what order were the subatomic particles discovered?
- Electron
- Nucleus
- Proton
- Neutron
How did Niels Bohr adapt the nuclear model of the atom?
He suggested that electrons orbit the nucleus at fixed distances
What did James Chadwick discover?
Neutrons
Why was Niel Bohr’s discovery of the electrons orbitting the nucleus at a fixed distance significant?
This discovery shows how because the negative electrons orbit the nucleus on electron shells this stops the atoms from collapsing
Why was gold used in the gold foil experiment?
Gold **can be flattened out **to a thickness of one atom thick so the particles can easily go through it
Define an isotope
An atom with the same number or protons but a different number of neutrons
Define an ion
An atom with the same number of protons but a different number of electrons
What is the defenition of a molecule?
A particle made up of two or more atoms that have been chemically bonded together
Why was Mendeleev’s Periodic Table widely accepted?
- He left gaps for unknown elements, when they were discovered, these elements fit the gaps
- Mendeleev predicted the properties of undiscovered elements correctly
What is the definition of an element?
A substance that is made up of only one type of atom
Who discovered the electron?
J.J Thompson
Why did Mendeleev reverse the order of some pairs of elements?
[1 mark]
So that the properties of the metal matched the rest of the group
