topic C1-Atomic Structure and the Periodic Table Flashcards
What is an atom?
An atom is the smallest part of an element
What is an element?
made up of only one type of atom
Elements may combine through chemical reactions to form new products; what are these new substances called?
compounds
What is a compound?
contains 2 or more different elements chemically combined in a fixed proportion
compounds can be separated by
chemical separation
What is a mixture?
A mixture consists of two or more elements or compounds not chemically combined together
mixtures are separated by
physical separations
What are the methods through
which mixtures can be separated
(there are five)? Do these involve
chemical reactions?
Filtration, crystallisation, simple distillation, fractional distillation chromatography they do not involve chemical reactions
Describe and explain filtration
separates insoluble solids from liquids
- filter paper placed in a funnel over a conical flask
- pour mixture through the funnel
- insoluble particles are left on the filter paper
Describe and explain crystallisation/evaporation.
used to separate a soluble solid from solvent by evaporation
-pour the solution into a evaporating dish
-gently heat the solution until all the solvent evaporates
-the solution
(crystallisation)
Crystallisation is similar, but we only remove some of the solvent by evaporation to
form a saturated solution Then,
we cool down the solution. As we do it, the solid starts to crystallise,
Required Practical 1 method-Making Salts
- using a measuring cylinder measure (20 cm of sulfuric acid ) of acid into a beaker
- add powdered metal into the acid and stir with a glass rod
- continue adding the powder until it is in excess so no more reacting occurs eg fizzing
- set up Filter using filter paper and funnel the solution to remove the excess solid (copper oxide.)
- Pour the solution into the evaporating dish.
- Evaporate the solution using a water bath until crystals start to form.
- Leave the evaporating basin in a cool place for at least 24 hours.
- Gently pat the crystals dry between two pieces of filter paper.
why do you need to put excess powder
so that no more reaction occurs
Describe and explain the simple distillation
Simple distillation is used to separate liquid from a solution – the liquid boils off and condenses in the condenser. The thermometer will read the
boiling point of the pure liquid.
the problem with simple distillation
if the solution of liquid have the same boiling point than the liquids cannot separate
explain
fractional distillation
Fractional distillation is a technique for separation of a mixture of liquids.
It works when liquids have different boiling points.
liquid with the lowest boiling point evaporates first
liquid with the highest boiling point condense at the bottom
simple distillation - method
- start off by heating the solution eg using a Bunsen burner
- the part of the solution with the lowest boiling point evaporates first
- the liquid turns into vapour and passes into the condenser
- the vapour then cools and condenses turning back into a liquid
- crystal solids are left behind in the flask and the liquid is collected in the beaker
fractional distillation - method
The apparatus is similar to the one of simple distillation apparatus, with the
additional fractionating column placed on top of the heated flask.
The fractionating column contains glass beads. It helps to separate the compounds. The column is hot at
the bottom and cold at the top. The liquids will condense at different heights of the column.
Describe and explain chromatography
Chromatography is used to separate a mixture of substances dissolved in a solvent.
paper chromatography, we place a piece of paper with a spot containing a mixture
in a beaker with some solvent. The bottom of the paper has to be in contact with
the solvent. The solvent level will slowly start to rise, thus separating the spot (mixture) into few spots (components).
john Dalton
thoughts that atoms are tiny solid spheres that cannot be divided
jj Thomson
discovered electrons which led him to the plum pudding model
Describe the plum-pudding model
The atom is a ball of positive charge with negative electron embedded in it.
Ernest Ruthford
the alpha scattering particles experiment
which led him to the conclusion that mass of an atom was concentrated at the centre (nucleus) and that the nucleus is a positively charged
alpha scattering particle
- a beam of alpha particles was fired at a thin gold foil
- most particles went straight through the gold foil
- some alpha particle was deflected and some repelled
what did the alpha scattering experiment tell us
most alpha particles went straight through therefore atoms are mainly empty space
some of the particles were deflected therefore the centre of an atom must have a positive charge
- empty space
- positive nucleus
- surrounded by electrons
Neil Bohr
suggested the nuclear model
- suggested that electrons orbit the nucleus at a certain distance
Describe the Bohr/nuclear model and how it came about
The nuclear model suggests that electrons orbit the nucleus at specific
distances (shells) – it came about from the alpha scattering experiments
later on the experiment
led to the discovery of protons - positive particle in the nucleus
James Chadwick
included that the nucleus contains neutrons
overview of the plum pudding model
- mainly empty space
- positive nucleus
- surrounded by negative electrons
overview of the nuclear model
electrons - orbit the nucleus at a specific distance - called shells or energy levels
the positive charge in the nuclear is due to tiny positive particles called protons
nucleus contains neutral particles called neutrons
State the relative charges
of the proton, neutron and electron
proton - +1
neutron- 0
electron - -1
State the relative mass
of the proton, neutron and electron
proton - 1
neutron - 1
electron -very small
What is the radius of an atom?
0.1 nm
