1.6 Periodic Table Flashcards
how are elements arranged
according to atomic number
vertical columns are
groups
horizontal rows
periods
trend in ionization energy across period
increases across a period because there is an increase in nuclear charge in the same energy level.
ionization energy down a group
decreases down a group because the outer
electron has increased shielding from inner electrons.
trend in electronegativity
increases across a period because there is an
increase in nuclear charge, but the bonding electrons are always shielded by the same inner electrons.
trend in melting and boiling point
generally increase from the first to the fourth element, followed by a large decrease to the fifth element and a small general decrease to the eighth element. This is because the bonding changes from metallic to giant covalent to simple molecular covalent.
oxidation
loss of electrons
reduction
gain of electrons
oxidising agent
is a species that accepts electrons; it becomes
reduced itself in the process
reducing agent
species that donates electrons; it becomes
oxidised itself in the process.
oxidised
if oxidation number increases
reduced
reduction number decreases
group 1 metals with water
react vigorously with cold water to form the
hydroxide and hydrogen.
group 2 metals with water
react less vigorously, in fact, magnesium reacts very slowly, while calcium produces a steady stream of bubbles and a
white precipitate of calcium hydroxide. Again, the hydroxide and hydrogen are formed
trend in reactivity
increases as you go down a group because when the s-block metals react they lose electrons to form positive ions. Since
ionisation energies decrease down a group, the energy needed to form positive ions decreases.
compare group 1 and 2 metals
Group 1 metals are more reactive than Group 2 metals because
they lose only one electron while Group 2 metals lose two2
group 1 and 2 reacting with oxygen
All Group 1 and Group 2 metals burn to form solid white oxides.
group 1 oxide and barium oxide reacting
Group 1 oxides and barium oxide react with water to form a soluble hydroxide or alkali.
soluble hydroxide ?
its an alkali
alkali?
soluble hydroxide
sodium flame test
orange yellow
lithium flame test
red
potassium flame test
lilac
calcium flame test
brick red
strontium flame test
crimson
barium flame test
apple green
solubility of group 1
soluble
solubility of group 2
non-soluble
trends for group 2 compounds
- All nitrates are soluble.
- All carbonates are insoluble.
- Hydroxides are more soluble as you go down the group.
solubility trend for sulfates
become less soluble as you go down the group
trend in thermal stability
increases as you go down the group
group 7 halogens
As the number of electrons increases with atomic number, there is an increase in the induced dipole – induced dipole intermolecular forces holding the diatomic molecule together. Thus, the melting
and boiling temperatures increase as you go down the group.
chlorine at room temp
green gas
bromine at room temp
red-brown liquid
iodine at room temp
grey solid
halogens react by gaining electrons
forms negative halide
during reactions what do halogens do ?
in reactions halogens are reduced and they oxidise the other substance
halogens down the group – sheilding?
As you go down the group the outer electrons are shielded more and are further from the nucleus.
halogens react directly with most metals to form
halides
displacement reactions
A halogen in a higher position in the group will oxidise a halide ion from lower in the group
how to test for halide ions
few drops of nitric acid to halide ions then add silver nitrate solution followed by diltute aq ammonia
test for halide ions
cl- chlorine
silver nitrate = white precipitates
diluted nh3 = ppt dissolves
test for halide ions
bromine
silver nitrate = cream precipitate
diluted nh3 = ppt dissolves slightly
test for halide ions
iodine
nitric acid = pale yellow precipitate
diluted nh3 = no change
chlorine in water treatment
Chlorine gas is added to drinking water to kill dangerous bacteria and viruses such as cholera and typhoid, thereby preventing
the outbreak of serious diseases.
It needs to be added in low concentrations (below 1 part per million) in order to be safe.
fluoride in water treatment
Fluoride is added to water to reduce tooth decay, by preventing cavities. It is also said to strengthen bones, which helps prevent osteoporosis.
Again, it appears to only have beneficial effects when added below 1 ppm.
how are insoluble salts formed
by a precipitation reaction
how are soluble salts formed
by neutralising an acid
what occurs in precipitation reaction
two suitable solutions are mixed to form a soluble salt and an insoluble salt.
For example, the formation of calcium carbonate
