atoms & periodic table Flashcards
what is an atom
chemical building blocks of the world
- made of electrons protons and neutrons
what is an element
a pure substance containing 2 or more of the same atom
what is a compound
2 or more atoms of different elements chemically bonded together
what is the law of conservation of mass
mass is neither created or destroyed in an equation so the total mass of the product should be the same as the total mass of the reactants. (why we balance)
filtration method
separating insoluble from solution
1. put filter paper in a funnel and place it in a test tube
2. pour solution into filter paper
3. solvent will be in the test tube, insoluble solid will remain in the filter paper
crystallisation method
when soluble need to be separated
1. heat up solution on evaporating basin
2. keep heating until most solvent has evaporated
3. remove from heat and leave near a window for a few days
4. once liquid has completely evaporated pat crystals dry with filter paper/ paper towel
distillation method
separating a solution made of 2 solvents
1. heat up solution using bunsen burner
2. solvent with lower boiling point will evaporate leaving 1 solvent behind
fractional distillation
when 2 liquids are bonded together and need to be separated
1. heat solution with bunsen burner
2. solvent with lower boiling point will evaporate and enter a cooling jacket
3. cools down and condenses again
4. goes into a separate beaker
paper chromatography
to separate + identify substances in a solution, compounds in a mixture dissolve at different rates.
- spot of solution is added on a pencil line near bottom of chromatography paper.
- paper is placed in a beaker of a solvent
- paper soaks up the solvent and runs through the added solution
- the further up a solution is on the paper, the more soluble it is in that solvent
who created the periodic table (JJD)
John Dalton 1808
John Newlands 1864
Dimitri Mendeleev 1869
John Dalton
- arranged the elements in order of weight
- thought elements were tiny spheres that couldn’t be divided
John Newlands
- created law of octaves, every 8 elements have similar properties
- table was not grouped
Dimitri Mendeleev
- left gaps for undiscovered elements
- swapped some around based on atomic weight
JJ Thompson
discovered the electron, made the plum pudding model
Rutherford, Geiger and Marsden
alpha particle experiment
- directed alpha particles at sheet of gold foil
- thought particles would all pass through
- some did, some deflected, some bounced back, led to discovery of nucleus
Niels Bohr
electrons orbit nucleus at specific distances in fixed energy levels (shells)
James Chadwick
proved existence of neutrons within nucleus
what is an atomic number
the number of protons and electrons in each atom, always the smaller number
what is the atomic mass
the total numbers of protons, neutrons and electrons
what is an ion
same number of protons but different amount of electrons
what is an isotope
same number of protons but different neutrons
the periodic table
the periodic table is an arrangement of elements where they are placed in the order of their atomic number in periods and groups
metals and non-metals
- metals tend to have higher boiling and melting points
- ductile (drawn out into wires) and malleable (moulded/ hammered into different shapes without breaking)
- non-metals found in top right (staircase thing)
groups
- groups 1,2,3 tend to lose electrons to form ions
(metals react by losing electrons) - group 5,6,7 gain electrons to form negative ions
(non-metals react by gaining electrons)
group 0 - noble gases
- have 8 electrons in their outer shells (except helium,2)
- all have full outer shells, so stable & very unreactive
- monatomic
- reactivity decreases
- boiling and melting points increase
group 1 properties
- very reactive, stored in oil
- reactivity increases
- boiling and melting points decreases.
- react with water > fizzing, hydrogen gas produced
- 1 electron in outer shell, lose to get positive ion
group 7 - halogens
- diatomic molecules (covalent)
- all have 7 electrons in outer shells (has to gain 1 )
- reactivity decreases as you go down
- boiling and melting points increase
what happens when the atoms get larger
- it is easier to lose electrons
- it is hard to gain (electrons in outer shell are further away and the attraction from the nucleus is weaker, called shielding)
transition elements
all metals (centre block between group 2&3)
- high densities
- high melting and boiling points
- conductors of heat and electricity
- good catalysts
what is the particle theory
everything is made up of tiny particles which cant be broken down any further
what are catalysts
increases the rate of reaction without being used up themselves
