atomic structure and the periodic table Flashcards
how big is an atom
generally, atoms have a radius of around 0.1 nm
what is an isotope
different forms of the same element that have the same number of protons but a different number of neutrons
how do you find the relative atomic mass of an element
sum of (isotope abundance x isotope mass) / sum of abundances of all isotopes
what is a molecule
a group of 2 or more atoms held together by chemical bonds
what is a compound
substances that contain 2 or more different elements held together by chemical bonds
what is a mixture
two or more substances that are not chemically combined together
what is filtration
a separation technique that can separate an insoluble solid from a liquid
how can you separate a soluble solid from a liquid
either by evaporation or crystallisation
what are the advantages and disadvantages of evaporation
- quick and easy
- however some solids decompose when heated
when is distillation used
when you need to separate mixtures that contain liquids
what equipment is used during distillation
- flask
- bung
- thermometer
- condenser
- water jacket
- beaker
- bunsen burner
what are the steps of simple distillation
- heat the solution until it reaches the boiling point of the liquid you want to separate
- the gas particles will condense in the condenser due to the cold water
- the liquid will then drip out into the beaker
what is a fractionating column
a tall container containing little glass rods, used during fractional distillation
what is the atomic theory
the theory that everything is made of tiny particles that can’t be broken down any further
what was john dalton’s theory about the atom (1800s)
dalton believed that atoms were solid sphere and that different types of spheres might make different elements
what was jj thompson’s theory (1897)
plum pudding model
- believed that atoms could not be solid spheres
- they were instead general balls of positive charge with discrete electrons in it
what experiment did ernest rutherford and his students carry out in 1909
they fired positively charged alpha particles at a thin sheet of gold
- if thompson’s theory was correct all the particles should have gone straight through
- however some particles were deflected partially and others directly sent backwards
what was rutherford’s theory about the atom
atomic model theory
- compact nucleus with all the positive charge
- negative charge in some sort of cloud
what was niels bohr’s idea
- negatively charged electrons orbited the nucleus
- electrons held in shells
who provided evidence for the existence of neutrons
james chadwick
what do atoms need to be stable
a full outer shell
what was dimitri mendeleev’s periodic table like
- arrange in order of increasing atomic number (number of protons)
- grouped with elements that had similar properties
- left spaces for undiscovered elements
why do elements in the same group have similar properties
they have the same number of electrons in their outermost shell which is what largely determines how an element reacts
why do metals become more reactive as you go down the group
the number of shells increases, meaning there is a greater distance between the outermost shell and the nucleus making it easier for the atom to lose electrons as the nucleus cannot hold onto them strongly
