The Periodic Table and Group Trends Flashcards
How to extract group 1 metals
extracted by electrolysis of molten compounds
what are the group 1 metals called
alkali metals
physical properties of alkali metals
soft - cut with knife
low melting and boiling points
surface is shiny/silvery grey but tarnishes quickly
floats on water
what type of bonding is used for group 1
metallic bonding - relatively weak compared with other metals
reactivity of group 1 metals
very reactive - stored in oil to prevent reaction with oxygen or water in the air
react vigorously with water forming
group 1 metals what happens to k
k is more reactive - catches fire, lilac flame, pops as hydrogen ignites
why does reactivity increase going down alkali metals
outer electron has to be lost to form positive ion. further the outer electron is from the nucleus, the less tightly it is held. it is shielded from the nucleus by full inner shells and so is more easily removed
what are group 7 metals known as
halogens
appearance of fluorine
gas - pale yellow green
appearance of chlorine
yellow green gas
appearance of bromine
red liquid (volatile)
appearance of iodine
silvery grey solid
why do halogens have low melting points
they are simple covalent molecules and only have weak intermolecular forces that need to be overcome
why do boiling points increase down the halogens
molecules get bigger so the intermolecular forces get stronger due to more electrons in the molecule
where must chlorine be used due to toxicity
fume cupboard
extraction of chlorine
electrolysis of concentrated NaCl solution (2NaCl + 2h2o -> 2NaOH + H2 + Cl2
extraction of bromine and iodide
from their salts by displacement using cl2
test for chlorine
damp blue litmus paper pink then bleaches it
uses of chlorine
killing bacteria
bleach in paper making
production of antiseptics
what do halogens react with h2 to make
hydrogen halides
what are the noble gases
group 0/8
have full outer shells of electrons so
do not react
exist as single atoms
how are noble gases obtained
fractional distillation of air
use of helium
weather balloons
airships - low density and flammability
use of argon
welding to stop hot molten metal oxidising
use of neon
fluorescent lights
use of ar/kr/xe
inert atmosphere in light bulbs so filament doesn’t burn
use of mixtures
in gas lasers (barcode readers)
how were noble gases discovered
density of nitrogen gas made in a chemical reaction was different to density of nitrogen obtained from air
what is the group number
number of outer shell electrons
what is period number
number of shells
bonding in metals
atoms held together by metallic bonding - electrostatic attraction between cations and a sea of delocalised electrons
bonding in non metals
molecules or giant structures held together by covalent bonds and a shared pair of electrons
difference of transition metals
can form more than 1 type of ion - fe2+/fe3+
higher mp and bp
form coloured compounds and solution
most give coloured precipitates when reacted with NaOH
coloured compounds in solution
fe2+ - green
fe3+ - yellow brown
cu2+ - blue
cr3+ - green