topic 1 - atomic structure + the periodic table Flashcards
what’s the radius of an atom?
around 0.1 nanometres ( 1 * 10^-10 m)
what’s the nucleus of an atom?
in the middle of the atom, it contains protons and neutrons and so has a positive charge. almost the whole mass of the atom is concentrated in the nucleus. the radius of the nucleus is around 1/10000 of the radius of an atom
what are electrons
negatively charged subatomic particle that orbit the nucleus in shells. they are tiny so have virtually no mass.
what are protons
positively charged subatomic particles that are found in the nucleus. they have a relative mass of 1
what are neutrons
neutrally charged subatomic particles that are found in the nucleus. they have a relative mass of 1
what are elements
they consist of atoms with the same atomic number
what are isotopes
different forms of the same element, which have the same number of protons but different numbers of neutrons
what’s the formula for relative atomic mass of isotopes
relative atomic mass = sum of (isotope abundance*isotope mass number)/sum of abundances of all the isotopes
what are compounds
substances formed from two or more elements, the atoms of each are in fixed proportions throughout the compound and they’re held together by chemical bonds
What is a mixture
Multiple elements or compounds that are not chemically bonded together and so can easily be separated out
What is chromotography used for
To separate different dyes in ink
What is filtration used for
To separate insoluble solids from liquids
What are two ways to separate soluble solids from solutions
- evaporation
- crystallisation
How can you separate rock salt
1) grind it
2) put the mixture in water so the salt dissolves
3) filter out the sand
4) evaporate the water
What is simple distillation used for
Separating out a liquid from a solution (e.g pure water from seawater)
Describe simple distillation
The solution is heated and the part of the solution that has the lowest boiling point evaporates first. The vapour is then cooled and condenses, and is collected.
What is the problem with simple distillation
It can only be used to separate things with very different boiling points
What is fractional distillation used for
Separating a mixture of liquids that can have similar boiling points
How does fractional distillation work
Heat the mixture under a fractioning column, the different liquids will have different boiling points and so evaporate and condense at different temperatures. Liquids with higher boiling points will condense quicker and so will not reach the top of the fractioning column. Lower boiling points will reach the top and drain out through the condenser. Then raise the temperature.
Who came up with the plum pudding model
JJ thomson
Who conducted the alpha particle scattering experiments
Rutherford
What were the results of the alpha particle scattering experiments
Some particles were deflected more than expected, disproving the plum pudding model. Rutherford came up with a new idea of the atom - positive nucleus surrounded by a cloud of negative electrons
What was the problem with Rutherfords model of the atom
The electrons would be attracted to the nucleus and the atom would collapse
Who added that electrons orbited the nucleus in shells
Bohr
Who discovered neutrons
James Chadwick
Why did Menderleev leave gaps in the periodic table
So elements with similar properties stayed in the same groups
What helped confirm Mendeleev’s periodic table
- the discovery of elements that fitted the patterns he predicted
- the discovery of isotopes
What are the properties of metals
- strong and hard to break
- Good conductors of heat and electricity
- malleable
- high melting and boiling points
What are the properties of non - metals
- dull looking
- more brittle
- don’t usually conduct electricity
- lower density than metals
What are the properties of transition metals
- can form more than one ion
- often coloured
- Good catalyst
- less reactive and much harder than group 1 elements
How do alkali metals react with water
Vigorously - producing hydrogen gas and metal hydroxides
How do alkali metals react with chlorine
Vigorously- to produce metal chloride salts
What does an alkali metal reacting with oxygen form
Metal oxides
What’s a displacement reaction
A more reactive element displacing a less reactive one
Why are group 0 metals unreactive
They have a full outer shell and exist as monatomic gases
