the periodic table Flashcards
before the 20th century, what could scientist measure regarding elements
relative atomic mass
what was noticed after arranging elements in order of mass
properties of elements where repeated at regular intervals
what are some problems with the early periodic tables
not all elements had been discovered so not compleate
ended up in the wrong group as they where placed in order of relative atomic mass
what did Dmitri Mendeleev do
1869
left gaps
mainly in order of atomic mass
but switched order of some elements
so elements with the same properties ended up in the same groups
the gaps allowed predictions to be made about undiscovered elements
what did the discovery of isotopes do
isopotops of the same elemnt have different atomic masses but the same chemical propeties so occopy the same place on the pt so mendeelev was right to leave gaps
what is the modern periodic table measured in
incresing atomic number
what does the period number tell you
how many electron shells
what does the group number tell you
how many electrons in the outer shell
what are metals
elements that form positive ions when they react
why cant non metals form positive ions
right of pt where they have lots of electrons to remove gto form a full outer shell or near the top where the outer shell elecrons have a strong force of attraction towards the nucleus.
physical properties of metals
strong
malible
great conductors of heat and elecricty.
high boiling and melting points.
physical properties of non metals
dull
brittle
lower bp and mp
lower density
what are the alkali metals and what are their properties
group 1: lithium, sodium, potassium, rubidium, caesium and francium
they are silvery solids that have to be kept in oil.
one elecron in their outer shells. low density and get more reactive down the group
why do alkali metels get more reactive down the group
elecron is further away from force of attraction of the nucleus
what happens to the boiling point going down group 1 elements
decreases down the group
what do the alkali metals make when they react with non metals
ionic compounds with a positive 1 charge.
the compounds are usually white solids that dissolve in water to form colourless solutions.
what is the equation for the reaction of alkali metals with water
alkali metal + water = metal hydroxide + hydrogen
why are the group 1 metals called alkali metals
the hydroxides formed when will dissolve in water to create alkali solutions
what is the equation for the reaction of alkali metals with chlorine
metal chlorine
its white
what is formed when alkali metals react with oxygen
metal oxide
what elements are the halogens
Florine , chlorine, bromine, iodine and astatine
how do the halogens exist in their natural state
in pairs
halogens are metals that have what coloured vapours
fluorine - poisonous yellow gas
chlorine - poisonous dense green gas
bromine - poisonous dense red brown volatile liquid or orange vapour
iodine - poisonous dark grey crystalline solid or purple vapour
what are the reactivity trends in the halogens
less reactive going down the group
because they react by gaining an electron
the outer shell is further away from the nucleus moving down the group so there is a smaller force of attraction from the nucleus
what is the boiling point trend for the halogens
increase down the group
what and how do halogens react with other non metals
other non metals
covalent bonds
the compounds formed have simple molecule structures
what are formed when a halogen reacts with a metal
halide ions
what do halogens do in displacement reactions
a more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt
name 3 noble gasses
helium, neon, argon
why are the noble gasses inert
full outer shell of electrons
what do noble gasses look like
colourless monatomic gases (single atoms not bonded)
why does the boiling point of noble gasses increase going down the group
going down the group atomic number increases so there are more electrons which causes the intermolecular forces between the atoms to increase
what are some properties of transition metals
good conductors of heat and electricity, dense, strong, shiny
compare transition metals with alkali metals
tm are less reactive
tm are denser, stronger and harder
tm have much higher melting points
why do transition metals form coloured compounds
due to the tm ion they contain.
e.g potassium chromate is yellow
potassium manganate is purple
do transition metals make good catalyst
yes
