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Groups of the periodic table - Coggle Diagram
Groups of the periodic table
group 1 - alkali metals
group one elements placed on left handside
tehy form alkaline solutions when reacted with water which is why theyre called alkali metals
lithium sodium and potassium all alkali metals
one electron on outer shell
first three elements
lithium - LI - atomic number 3
sodium NA - atomic number 11
Potassium K - atomic number 19
physical properties of alkali metals
lower melting and boiling points
one electron in outer shell held very weakly by nucleus - electron can drift further from nucleus than in most elements waeaker bonds, dont require alot of energy to break
The decrease in melting and boiling points down the group can be explained by the additional shell being added to the previous element causing the atomic radius to increase. The increasing atomic radius means weaker forces between the atoms and so a lower melting and boiling point.
alkali metals are soft
alkali metals are soft metals which can be cut with a knife and are silverly coloured
freshly cut alkali are shiny but tarnish rapidly because of the oxyen in the air , genrally stored under oil
It is the reduced interatomic forces in these elements that make them relatively soft.
good conductors of electricity and heat
Alkali metals have one electron in their outermost shell which is held very weakly by the nucleus. The outer electron can drift further from the nucleus and move relatively freely. On the application of an electric field the large numbers of free flowing electrons in the outer shells conduct electricity through the metal.
Similarly, on the application of heat the free moving electrons in the outermost shells gain a lot of energy and transfer this through the metal via collisions with the other free moving electrons.
alkali metals have a low density
Lithium, sodium and potassium are less dense than water and therefore can float on water. Rubidium and caesium are denser than water.
chemical properties of alkali metals
the alkali metals are the most reactive elements in the periodic table, they contain one elctron in their outershell which is readily transferred in chemical reactions
reactions of alkali metals with water
all group 1 elements react vigerously with water, they react with waterto form hydrogen gas and an alkaline solution of the metal hydroxide
In a reaction, an atom of a Group 1 element loses one electron and forms an ion with a single positive charge
process of losing an electron is termed as oxidation
The reactivity of the alkali metals increases going down Group 1.
reactions od alkali metals with chlroine
all group 1 metals react vigerously with chlorine , they react with chlorine to form white crystalline salts
lithium
if piece of hot lithium lowered into jar of chlorine, vigerous reaction takes place, forming white powder which sets on either side of the jar
this is the slat lithium chloride 2Li(s) + Cl2(g) → 2LiCl(s)
sodium
The reaction of sodium with chlorine is more vigorous than lithium. If piece of hot sodium is lowered into a jar of chlorine, the sodium burns with a bright yellow flame forming clouds of white powder that settle on the sides of the jar. This is the salt sodium chloride (NaCl).
potassium
Potassium reacts more violently with chlorine than sodium does, showing how reactivity increases down the group. The salt potassium chloride (KCl) is produced by this reaction. The reaction can be written as:
why does reactivity of group 1 elements increase going down the group
this is because going down the group...
atoms getting larger, weak attractive force between nucleus and electron so electron more easily given up
flame colours in alkali metals
Alkali metals emit distinctive flame colours when heated. These flame colours are used to identify these elements.
A small piece of metal compound is taken on the end of a Nichrome wire and introduced into a Bunsen flame. The flame emitting from the end of wire will show a distinctive colour that is characteristic of the metal in the compound. By referring that flame colour to the table below, we can identify the element in that compound.
flame colours of group elements
lithium - red
sodium - yellow
potassium - lilac
safety precautions for handling alkali metals
group one metals react with water to form hydroxide which dissolves in wtaer to form alkaline solutions
strong alkalis are corrosive , they must be stored under oil to keep water and oxygen from air away
must be handled safely, wearing goggles and gloves
group 7 - halogens
places in vertical collumn second from right handside of periodic table
all group 7 elements have 7 electrons in their outer shell
flourine chlorine, bromine and iodine all belong to group 7
group 7 elements form salts when they react with metals - the term halogen means salt former
structure of halogens
halogens consist of diatomic molecules , this means they exist as molecules each with a pair of atoms eg chlorine cl2
physical properties of halogens
colour
it can be inferred that the depth of colour of halogens increases in atomic number
flourine is a pale yellow
chlorine is green
bromine is orange
iodine is grey
melting and boiling points
the halogens belong to non metals and thus they have low melting and boiling points
the melting and boiling points increase as you go down the group
this is because more energy is needed to break the strong forces of attraction
flourine has the lowest melting and boiling point
chemical properties of halogens
reactivity of halogens
halogens get less reactive going down the group
Fluorine is the most reactive element in Group 7. In fact it is the most reactive of all non-metals.
reactions of halogens with alkali metals
the halogens react w metals to make salts called metal halides
metal + halogen = metal halide
The reaction between sodium and a halogen becomes less vigorous down the group. Fluorine reacts violently with sodium at room temperature. Chlorine reacts very vigorously when in contact with hot sodium. Iodine reacts slowly with hot sodium.
displacement reactions and the reactivity series
the reactivity of halogens decreases down the group
test for reactivity with chlorine
to each test tube add small amount of chlorine solution
the chlorine solution shows no raction with flourine which means flourine more reactive as its not displaced by chlorine
uses of halogens
...
flourine
flourine compounds are added ot toothpaste to prevent tooth decay
in some places flourine is added to water supply
chlorine
liquid chlorine is added to water at low concentration to kill bacteria
same way added to swimming pools to kill bacteria
chlorine is used as a bleaching agent, chlorine interacts with oxygen to reduce dyes and pigments to colourless compounds
bromine
Bromine is used in the manufacture of pesticides and fumigants
silver is used as a component of islver films
iodine
component of several dyes
iodine dissolevd in alcholol used as antispectic put on cuts
safety
Because the halogens are very reactive and poisonous, care must be taken when using them. Chlorine is used only in a fume cupboard. Iodine should not be handled with bare hands. Gloves and goggles should be worn while handling reactive chemicals.
group 0 - noble gases
the group 0 chemicals are placed in the rightmost collumn of the periodic table
theyre called the noble gases because theyre all chemically unreactive because their atoms have stable arrangments of electrons. Aa=ll noble gases have the maximum number of electrons in the outer shell
noble gases are monoatomic which means they exst as single atoms
propeerties of noble gases
noble gases are all non metalllic elements
they are colourless gases at room temperature and pressure with very low melting and boiling points
non metals
unreactive gases
colourless, odorless and non reactive
boiling point
the noble gases all have low boiling points helium has lowest boiling point of the group
However, for the noble gases the significantly low boiling points are due to the weak interatomic forces between the monatomic atoms. The boiling points increase down the group. The weak interatomic forces increase as the size and mass of the atoms increases.
density
the density of a substance is a measure of how heavy it is for its size
the partcles in gases are spread far apart so the noble gases have low densities
uses of noble gases
Due to unreactive nature, low density and non-flammability of noble gases, they have a variety of uses listed below:
helium
filling airships and baloons
heliium much less dense than air so used in balloons
he low boiling point of helium makes it a very useful coolant. Helium boils at -269°C which is only 4°C above the lowest temperature achievable in theory called absolute zero (-273°C). Helium is used to cool metals down to very low temperatures so that they lose their electrical resistance and become super-conductors.
ecause helium is unreactive, it is used to provide an inert protective atmosphere in the manufacture of fibre optics and semi conductors.
Neon
neon is used in advertising signs also known as neon signs
neon glows a reddish orange colour when electricty is passed through it
argon
Argon is used in incandescent light bulbs instead of air as it will not react with the tungsten filament even when it is white hot.
Krypton
Like argon, krypton is used commercially to fill energy saving fluorescent lights.
Krypton lasers are used by surgeons to treat certain eye problems and to remove birthmarks.