atoms (required practical) Flashcards
what is the radius of an atom?
0.1 nanometres 1x10^-10
what are the properties of a nucleus?
in the middle of the atom.
contains protons and neutrons.
radius of 1x10^-14. 1/10,000 of the radius of the atom
positive charge. because of protons
contains almost all the atoms mass.
what are the properties of electrons?
move around the nucleus in electron shells.
negatively charge.
tiny but cover a large area.
almost no mass.
the volume of their orbit is the size of the atom.
why are atoms neutral?
there is the same amount of protons and electrons. +1 and -1
why does an ion have a charge?
there is not the same amount of protons and electrons.
how is the atomic number different the the mass number of an atom?
the atomic number the bottom number shows the amount of protons.
the mass number the top number shows the amount of neutrons and protons.
how do you calculate the number of neutrons in an atom?
the mass number - the atomic number. protons and neutrons - protons
what is an element?
a substance made of atoms with the same proton number.
how many different elements are there?
~100. this is just for fun
what is an isotope?
an element with extra neutrons. same atomic number different mass number
what is the formula for the relative atomic mass of an element?
relative atomic mass = (isotope abundance x isotope mass number) ÷ total isotope abundance abundance = amount
what is a compound?
a substance formed of 2 or more chemically bonded elements.
how is a compound formed between a metal and a non metal?
the metal atoms lose electrons to form positive ions.
the non metal atoms gain electrons to form negative ions.
the opposite charges attract. ionic bonding
how is a compound formed between 2 non metals?
each atoms shares an electron with another atom. covalent bonding
what do chemical equations show?
chemical changes.
such as methane + oxygen → carbon dioxide + water
what do symbol equations show?
the atoms in a reaction. balanced
such as 2Mg + O₂ → 2MgO
what is a balanced equation?
a symbol equation with equal atom amounts on both sides.
what is a mixture?
a substance formed of 2 or more non bonded elements or compounds.
how do you do paper chromatography? to separate substances in a mixture (required practical)
- draw a horizontal line near the bottom of a sheet of filter paper. use pencil
- add a spot of ink to the line and stand the paper in a beaker of solvent not touching the ink. e.g. water
- place a lid on the beaker to stop the solvent evaporating.
- each dye in the ink will move up the paper at a different speed.
- when the solvent has nearly reached the top of the paper remove the paper and let it dry.
- the end result is a pattern of spots called a chromatogram.
how do you separate soluble liquids from solutions?
evaporation. heat the solution in an evaporating dish with a bunsen until dry crystals
crystallisation. heat the solution in an evaporating dish until some crystals form and leave to cool
how do you separate liquid from a solution with simple distillation? (practical)
set up a distilling flash suspended over a flame.
connect a condenser to the distilling flask’s side arm. with the water out being higher than water in
place a beaker at the end of the condenser to collect liquid.
how do you sperate liquid from a mixture of liquids with fractional distillation? (practical)
add a mixture to a round bottom flask and connect a fractionating column to the top with a thermometer at the top.
liquids have different boiling points and so evaporate at different temperatures.
place a flame beneath the flask and heat to the lowest boiling point in the mixture.
when the first liquid has been collected raise the temperature until the next one reaches the top of the fractionating column.
who helped develop the atom model in order and what did they say?
john dalton. atoms are solid spheres
jj thomson. ball of positive charge with electrons stuck inside (plum pudding)
ernest rutherford. *tiny positive nucleus at centre and cloud of electrons (nuclear model)
niels bohr. electrons orbit the nucleus in fixed shells
james chadwick. discovery of neutrons in nucleus
what are the electron shell rules?
electrons are in shells. also called energy levels
the lowest shells are filled first. closest to the nucleus
2 electrons in the first shell 8 in the second and third.
in most atoms the outer shell is not full. which makes the atom want to react to fill it
what is a molecule?
a group of 2 or more atoms help together by covalent bonds.
