P1- Topic 1-Atomic structure and the periodic table Flashcards
what is an element
an element is a substance of only type of a atom
what is a compound
two or more elements combined chemically in fixed proprtions
what is a mixture
two or more elements not chemically combined together
it has the same chemical properties
what 5 ways mixtures can be separated
fractional distillation chromotography simple distillation crystallisation filtration
describe and explain simple distillation 3
Simple distillation is used to separate liquid from a solution
solution heated, solution with lowest boiling point evaporates first.
the liquid boils off and condenses in the condenser.
vapour travels through the condenser and turns into a pure liquid.
Describe and explain
crystallisation 7
Evaporation (e.g. salt from H2O).
used to separate a soluble solid from a solution
solution is heated until all the solvent evaporates; the solids stays in the evaporating dish
heated using a bunsen burner or water bath
cool down the solution.
the solid starts to crystallise,becomes concentrated
crystals collected and separated
from the solvent by filtration.
Describe and explain
fractional distillation
Fractional distillation for the separation of a mixture of liquids with different boiling points
fractionating column placed on top of the heated flask.
lowest boiling point evaporates first.
condenses at the top of the column and can be collected
mixtures are repeatedly condensed and vapourised.
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
filtration 4
to separate an insoluble solid from a liquid
insoluble solid gets caught in the filter paper,
because the particles are too big to fit through the holes in the paper.
The filtrate is the substance that comes through the filter paper.
Apparatus: filter paper + funnel.
Describe and explain chromatography
used to separate a mixture of substances dissolved in a solvent.
pencil line drawn 1cm from bottom
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, separating the spot(mixture) into few spots (components).
Describe the plum-pudding model
1
The atom is a ball of positive charge with negative electron embedded in it.
Describe the Bohr/nuclear model and how it came
about 2
The nuclear model suggests that electrons orbit the nucleus at specific
distances (shells) – it came about from the alpha scattering experiments
Later experiments led to the discovery of
smaller, positive particles in the nucleus; what
are these particles called?
Protons
why the new evidence from the scattering experiment led to a change in the atomic model
2
the positively charged alpha particles were being repelled and deflected
-by a tiny concentration of positive charge in the center of the atom (the nucleus).
Difference between the plum pudding model and nuclear model of an atom
-in the nuclear model negative electrons are not embedded in it rather orbit the nucleus
Describe the structure of an atom
The atom has a small central nucleus (made up of protons and neutrons)
around which there are electrons
State the relative masses and relative charges
of the proton, neutron and electron
Masses: 1, 1, very small ; Charges: 1, 0 , -1 (respectively
Explain why atoms are electrically neutral.
They have the same number of electrons and protons
What is the radius of an atom?
0.1 nm 1*10-¹⁰
What is the radius of a nucleus and what is it
compared to that of the atom?
1 x 10^-14 m and 1/10,000
What is an isotope? Do isotopes of a certain
element have the same chemical properties?
2
Atoms of the same element (same proton number) that have a different
number of neutrons.
same chemical properties as they have the same electronic structure
What are ions?
2
Ions are charged particles
formed when atoms lose electrons
(positive ions) or gain (negative ions) electrons.
