Atomic Structure and the Periodic Table Flashcards
What are atoms?
- smallest part of an element
- radius of about 0.1 nanometers (1 times 10 to the power of -10)
What are the relative masses and charges of the three particles in atoms?
Proton- relative mass of 1 and charge of +1
Neutron- relative mass of 1 and charge of 0
Electron- relative mass of very small (0 basically) and a charge of -1
What is the overall charge of an atom and why?
- Atoms are neutral (they have no overall charge)
- This is because they have the same number of protons and electrons
- Protons and electrons have opposite charges of the same size so they cancel each other out
What is the difference between an ion and an atom?
- In an ion the number of protons doesn’t equal the number of electrons
- An ion has an overall charge due to lost or gained electrons
What is an atomic number?
the number of protons in the atom
What is a mass number?
the total number of protons and neutrons that there are in an atom
What is an element?
A substance made up of only one type of atom (fixed number of protons in each atom)
What are isotopes?
- Isotopes are different forms of the same element
- They have the same number of protons but a different number of neutrons
- This means they have the same atomic number but a different mass number
What is the formula for working out the relative atomic mass of an element?
relative atomic mass=
sum of abundances of all the isotopes
What are compounds?
-Compounds are substances formed from two or more elements chemically combined in fixed proportions and positions
How do you separate the elements out of compounds?
Through chemical reactions
Do compounds have similar properties to the elements they are made of?
-No, they are usually totally different
How do we show what atoms are in a compound?
-We use formulas that are made up of elemental symbols in the same proportions that the elements can be found in the compound
What is the formula for Ammonia?
NH3
What is the formula for Sodium Chloride?
NaCl
What is the formula for Hydrochloric acid?
HCl
What is the formula for Calcium Chloride?
CaCL2
What is the formula for Sodium Carbonate?
Na2CO3
What is the formula for Sulfuric Acid?
H2SO4
What are reactants?
-Reactants are the molecules and ions and elements on the left hand side of the arrow in a chemical reaction equation because they react with each other
What are products?
-Products are the molucules and ions on the right hand side of the arrow in a chemical reaction equation because they have been produced from the reactants
What are mixtures?
two or more elements or compounds not chemically combined
Name the physical methods for separating parts of a mixture out:
- Filtration
- Crystallisation
- Simple Distillation
- Fractional distillation
- Chromatography
What are the properties of a mixture?
The properties of a mixture are just the properties of the separate parts. The chemical properties of a substance aren’t affected by it being a mixture
When can filtration be used?
If an insoluble product needs to be separated from a liquid reaction mixture. It can also be used in purification
How is filtration carried out?
The mixture is placed in cone shape filter paper which is in a funnel and a beaker. The liquid molecules are small enough to pass through the filter paper but the solid product does not and thus, separating them.
What is a solid that can be dissolved?
A solute
How are soluble salts separated from a solution?
Using crystallisation or evaporation
What is distillation?
A process used to separate mixtures which contain liquids.
What is the simple distillation process?
1) Solution is heated. Part of the solution which has the lowest boiling point evaporates first.
2) The vapour is cooled by cold water flowing around the tube (condenser) in which the vapour is travelling through from where it evaporated
3) The vapour condenses and is collected
4) The rest of the solution is left behind in the flask
What is the disadvantage of the simple distillation process?
It can only be used to separate things with very different boiling points
What is the fractional distillation process?
1) The mixture is put in a flask and a fractionating column is put on top. It is then heated.
2) The different liquids evaporate at different temperatures
3) The liquid with the lowest boiling point evaporates first and when the temperature on the thermometer matches the boiling point of this liquid it will reach the top of the column.
4) It will then go through a condenser and be collected
5) The liquids with higher boiling points will only get part the way up the column before condensing and running back down towards the flask
6) Once the first liquid has been collected, the temperature is raised until the next liquid reaches the top of the column and so on
What did JJ Thomson in 1897 discover about atoms?
He discovered that atoms were not a solid sphere. After measuring the charge and mass of an atom, he found that an atom must contain even smaller, negatively charged particles called electrons.
What theory did JJ Thomson devise?
the plum pudding model
Who proved that the ‘plum pudding model’ was wrong and how?
Ernest Rutherford and his student Ernest Marsden using the famous alpha particle scattering experiment
What is the alpha particle scattering experiment?
It is the firing of positively charged alpha particles at an extremely thin sheet of gold.
What did the Ernests expect to happen in the Gold Leaf Experiment?
They expected the particles to pass straight through the sheet or be slightly deflected at most. This was because the ‘plum pudding’ theory led them to believe that the positive charge of each atom was spread out throughout the ‘pudding’ of the atom.
What actually happened in the Gold Leaf Experiment?
Most the particles did go through the gold sheet but some were deflected more than expected. A small number were also deflected backwards. The plum pudding model couldn’t be right
What theory did Rutherford come up with to explain this new evidence?
He came up with the nuclear model of an atom
What is Ernest’s nuclear model of an atom?
In the model, there is a tiny positively charged nucleus at the centre, where most the mass is concentrated. A ‘cloud’ of negative electrons surround the nucleus so most the atom is empty space.