atomic structure and the periodic table Flashcards
what is an element
a substance containing only one type of atom
what is a compound
when two or more elements are chemically combined in a fixed propotion
what is a mixture
when elements or compounds are not chemically combined
what is used to separate a mixture
a physical separation technique
what is filtration used for
it is used to separate an insoluble solid from a liquid
what do we call the liquid that passes through the filter paper
it is called a filtrate
what do we call the leftover solid in the filter paper
the residue
what is crystallization used for
to separate a soluble solid from a liquid
what is simple distillation used for
it is used to separate a soluble substance from a liquid if we want to keep the liquid
what is fractional distilation
it allows us to separate two mixed liquids
what does a fractionating column do
it ensures that the vapors of the higher boiling point chemical condense back into a liquid into the flask
how does fractional distillation work
first both vapors of both liquids are going up the fractionating column although there is more of the lower boiling point liquid. Then as the lower boiling point is reached it becomes pure vapors of liquid A. This leaves liquid B to be collected when its boiling point is reached
what is a solvent
a solvent is a liquid that will dissolve substances
what is the stationary phase in chromatography
the paper
what is the mobile phase
the solvent
why does paper chromatography work
it is because each chemical will be attracted to the paper to different extents. strongly attracted chemicals wont move far and weakly attracted chemicals will move further
what is the plum pudding model
it is when a ball of positive charge has electrons scattered througout it
why did scientists use gold for the alpha particle scattering experiment
it is because gold can be hammered into thin sheets
why did they use alpha particles
it is because they have a positive charge
what is the nuclear model
the nuclear model has a positive nucleus with a ring of electron and is mostly empty space. Finally it changes to the current model
what is the relative mass of an electron
very small or insignificant
what is an isotope
isotopes are atoms of an element that have different numbers of neutrons but the same amounts of protons and electrons
what are ions
they are atoms that have either gained or lost electrons so have an overall charge
what was Johann Döbereiner’s theory
He believed elements with similar properties existed in three and he called these triads. the mains ones he noticed were lithium sodium and potassium. Also he found chlorine, bromine and iodine
what was John Newlands theory
he believed that every 8th elements ordered in atomic weight would have similar properties
why was Mendeleev table correct
It is because he predicted where the element would be and predicted their properties
what are the properties of noble gasses
they are very unreactive
they
what happens to the boiling point as you go down group 0
it increases
what two categories can you class the metals into and where are they found on the periodic table
highly reactive metals are group one and two
transition metals are found between group 2 and three
