C1 ATOMIC STRUCTURE AND THE PERIODIC TABLE Flashcards
what is an atom?
smallest part of an element what can exist
what is an element?
substance of only one type of atom
how are the elements listed and approx how many are there?
listed in the periodic table , approx 100
elements can classified into two groups on their properties; what are these groups?
metals and non metals
elements may combine through chemical reactions to form new products; what are these substances called?
compounds
what is a compound?
two or more or more different elements chemically combined in a fixed proportion
what is a mixture?
different elements or compounds not chemically combined together
what are the methods through which mixtures can be separated? do these involve chemical reactions?
filtration , crystallisation, simple distillation , fractional distillation and chromatography
they do not involve chemical reaction.
describe and explain simple distillation?
used to separate liquid from a solution
Salty water is heated
The water vapour cools in the condenser and drips into a beaker
The water has condensed and is now in the beaker, the salt stays behind
describe and explain crystallisation?
used to produce solid crystals from a solution. When the solution is warmed, some of the solvent evaporates leaving crystals behind.
A solution is placed in an evaporating basin and heated with a Bunsen burner.
The volume of the solution has decreased because some of the water has evaporated. Solid particles begin to form in the basin.
All the water has evaporated, leaving solid crystals behind.
describe and explain fractional distillation?
separate different liquids = a mixture of liquids.
Fractional distillation works because the different liquids have different boiling points.
When the mixture is heated:
vapours rise through a column = hot bottom,= cooler top
vapours condense when they reach a part of the column = below the temperature of their boiling point
each liquid is led away from the column
describe and explain filtration?
Filtration is used to separate an insoluble solid from a liquid.
1. One beaker contains a mixture of solid and liquid, the other contains a funnel with filter paper
2. The solid and liquid mixture is poured into the filter funnel
3.The liquid drips through the filter paper but the solid particles are caught in the filter paper
describe and explain chromatography
used to separate a mixture of substances dissolved ina solvent.
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 start to rise thus separating the spit into few spots
separating funnel?
a glass funnel with a tap at the bottom. two liquids that do not dissolve in each other. Liquids that do not dissolve in each other are called immiscible.
describe the plum pudding model?
the atom is a ball with positive charge with negative electron embedded in it.
describe bohr/nucleur model and how it came about?
the nuclear model suggests that electrons orbit the nucleus at specific distances - it came about from alpha scattering experiments.
what are the positive particles in the nucleus called?
protons
what work did james chadwick provide evidence for?
neutrons in the nucleus
structure of an atom?
has a small central nucleus (made up of neutrons and protons)
around which there are electrons
relative masses and charges of proton neutron and electron?
proton = 1 (mass) +1 (charge)
neutron = 1 (mass) 0 (charge)
electron = very small -1 (charge)
why do atoms have no overall charge?
because the number of electrons is the same as the number of protons
radius of atom?
0.1nm
radius of nucleus?
1 x 10 -14 m
what name is given to the number of protons in the nucleus?
atomic number
atoms of the same element have the same number of which particles in the nucleus?
protons
majority of mass of an atom?
nucleus
mass number?
total number of protons and neutrons
how do you calculate number of neutrons?
subtract the atomic number from the mass number
what is an isotope?
atoms of an element with different numbers of neutrons
what is an ion?
atoms which have no overall charge , they have gained or lost electrons
has positive ion gained or lost electrons?
lost
has negative ions gained or lost electons?
gained
relative formula mass?
the average of the mass numbers of the different isotopes
formula of ram
(mass number of isotope 1 X percent abundance of isotope 1) + (mass number of isotope 2 X percent abundance of isotope 2)/ 100
compare the properties of metals?
boiling/melting point = high (strong forces of attraction)
conductivity = heat and electricity (delocalised electrons)
appearance = shiny
maleabillity = yes (layers of atoms can slide over eachother whilst maintaining)
density = high
oxides = basic
compare the properties of non metals?
boiling/melting point = low
conductivity = don’t conduct heat and electricity (with the exception of graphite)
appearance = dull
malleability = brittle
density = low
oxides = acidic
what is ionic compound
metal + non metal
what is covalent bonding?
non metal + non metal
solute?
A solid substance that dissolves in a liquid
solvent?
dissolve in a given amount of liquid,
solution?
when a solute is dissolved in a solvent.
miscible?
substances that can mix together
immisicle?
substances that cannot mix together e.g water and oil
soluble?
substances that can be dissolved in a solvent.
insoluble?
won’t dissolve in a particular solvent.
the columns of the periodic table are called?
groups
the rows of the periodic table are called?
periods
are elements in the same group similar
they have similar chemical properties as they have the same number of outer electrons
what are the differences between elements of the same period (in terms of energy levels)
same number of energy levels
group 0 are called…
noble gases
what makes the periodic table periodic
the elements are arranged in columns (groups) and rows (periods).
elements that have the same number of electrons in the outer shell.. what does this tell us about the chemical properties?
similar chemical properties.
in terms of shell what is the difference between elements in the same period?
same number of shells
what change in shell number is seen as one moves down the group?
number of shell increases.
early periodic table were incomplete and elements were placed in appropriate groups if what was to b followed?
strict order of atomic weights
knowledge of what made it possible to explain why the order based on atomic weighs was not always correct?
isotopes
what did mendeleev do?
developed the first modern periodic table
started by arranging all the elements in order of increasing atomic weight.
mendeleev realised some elements have not been discovered so he simply left gaps in his periodic table where he thought an element was missing.
he was so confident that his table was correct that he actuallu predicted the properties of the undiscovered element based on other elements in the same group.
several years later these elements were discovered their proporties matched mendeelevs predictions because of that other scientists accepted that mendeelev table was correct
majority of the elements are…
metals
what are group 1 metals known as
alkali metals
3 characteristics of alkali metals?
one electron in the outer shell.
low density
stored under oil
how do group 1 elements react with non metals?
why are these reactions similar for the different group 1 elements?
form ionic compound (soluble white solids form colourless solutions)
they have one electron in the outer shell
how does group 1 react with water?
release hydrogen and form hydroxides which dissolve to form alkaline solutions: react vigorously (powerful) with water fizzing and moving around on the surface of the water
how does reactivity change moving down group 1
react more rapidly
outer electron is less attracted to the nucleus and easier to lose.
greater distance between the positive nucleus and the negative outer electron
outer electron is shield from the nucleus by the internal energy levels.
3 characteristics of group 7 metals
7 electrons in the outer shell.
coloured vapours.
form ionic salts with metals.
state group 7 elements and states of matter of molecules they form.
F F2 - fluorine
Cl Cl2 - chlorine
Br Br2 - bromine
I I2 - iodine
3 changes that occur in group 7 as one move down the group
higher relative molecular mass
higher melting and boiling point
less reactive - less easily gain electrons
compare group 1 metals with transition metals
g1 metals and transition metals are heat and electricity conductor , they are shiny when polished and form ionic compounds with non metals.
trans metal has higher densities and have higher melting points than group 1 metals , they are less reactive and harder than group 1 metals
3 characteristics of transition metals
ions with different charges
coloured compounds
catalytic properties
catalyst?
chemical substance that increases the rate of a chemical reaction.
state the colour of flames observed when lithium , sodium , potassium burn in oxygen
crimson - red , lithium
yellow orange - sodium
lilak - potassium
properties of noble gases?
non metals
gases
low boiling points
unreactive
the boiling point increases down the group as the atoms get heavier.
