Atomic Structure and the Periodic Table Flashcards
There are about ……. different elements
100
an element consists of
all the same atoms
define compound
Compounds contain two or more elements chemically combined in
fixed proportions
do compounds have similar or different properties to the elements their made of ?
usually totally different properties
Compounds can only be separated into elements by ……………….
chemical reactions
define mixture
A mixture consists of two or more elements or compounds not
chemically combined together.
Mixtures can be separated by
physical processes/ techniques
give 5 examples of physical processes of separation
filtration,
crystallisation,
simple distillation,
fractional distillation
chromatography
define molecule
a molecule has ANY element chemically combined
eg Ca(OH) 2 this is a compound AND a molecule
Cl2 is a molecule
how many atoms of each in this compound ? Ca(OH)2
1 Ca
2 O
2 H
physical separation techniques are used to separate …………… they cant be used to separate the ………….. in a ……………..
physical separation techniques are used to separate mixtures they cant be used to separate the elements in a compound
what is filtration used to separate
insoluble solid from liquid
what does (aq) mean
aqueous, dissolved in water
how do you filter
what do you need to filter
get filter paper and funnel and beaker
pour solution through filter paper and funnel
insoluble solid left in filter paper
liquid left in beaker
what is crystalisation used for
separate a soluble solid from a liquid
describe the process of crystallisation
heat solution in beaker till solvent evaporates
Crystals of the solid left in beaker
pour/ filter excess solvent
dry crystals in oven / pat with filter paper
what is simple distillation used for
simple distillation used for separating a solid from liquid if we want to keep the liquid
2 stages of simple distillation
evaporate liquid by heating
condense vapour by cooling
process of simple distillation (4 steps)
- place solution ( liquid + solid ) in conical flask
flask connected to glass tube which is surrounded by condenser - heat solution till liquid evaporates
- vapour passes through condenser
( condenser kept cold by circulation of water around it ) - condensed liquid collected in beaker
- crystals in flask and liquid in beaker
what can simple distillation be used for and a con of this
to produce drinking water from sea water
requires a great deal of energy
what is fractional distillation used for
separating a mixture of different liquids with different boiling points
how is the set up for fractional distilation different to the set up for simple distillation
the flask containing mixture is connected to a fractionating column (long column with hundreds of glass beads)
process of fractional distillation
. gently heat mixture
. both liquids start to evaporate
(lowest bp evaporate easier)
. mixture of two vapours making way up
fractionating column
. vapours hit fractionating column, they condense + drip back into flask and evaporate again
. repeated evaporation and condensation increases amount of lower b.p chemical in fractionating column
.warm vapours past column and reach thermometer (temp of thermometer rises)
-mixture passing thermometer has more of low b.p vapour
-vapours pass into condenser and becomes a liquid.
(still a mix of two chemicals)
-temp of thermometer reaches boiling point of lower bp chemical and stops rising
-swap to new flask, now much more lower bp chemical is evaporating and condesing into flask -(Higher bp chemical isnt evaporating or condensing much)
-we get our first pure sample of low bp chemical
-Temp of thermometer rises again-
mixture of vapour condenses into beaker(more high bp then low)
- when temp is constant, swap to new beaker- relatively pure sample of high bp chemical is collecteted
what does chromatography do
separate substances based on different solubilities
how can chromotography be used to find out which pens contain a mix / one colour
draw pencil line on chromatography paper - near bottom
put dot of first colour on pencil line and dot of second next
place bottom of paper in solvent
solvent makes its way up paper dissolves ink in coloured dots
ink is carried up paper as well
what is the stationary phase
the paper, it does not move
what is the mobile phase
solvent is the mobile phase as it moves
how to tell if a dye is pure
a pure compound will produce a single spot in all solvents
how to tell if a dye is a mixture
compounds in a mixture may separate into different spots depending on the solvent used
why does paper chromatography work
different substances have different solubilities . A more soluble substance travels further up the paper than a substance that is less soluble. That way we can seperate substances based on solubility
why do we draw our staring line in pencil
if we drew line in pen, pen ink would move up the paper, with the solvent
how do you measure distance moved by chemical
from pencil line to centre of spot
Rf value =
distance moved by substance / distance moved by solvent
no unit…
how to identify an unknown substance
workout Rf value and compare to datatbase
if 1+ substances have this Rf value than compare it in other solvents
in chromatography, what would you do if different substances have the same rf value
repeat with different solvent
Before the discovery of the electron, atoms were thought to be …………………
tiny spheres that could not be divided
The plum pudding model suggested that the atom is a ……………………..
ball of positive charge with negative electrons embedded in it.
the discovery of which subatomic particle led to the plum pudding model
The discovery of the electron led to the plum pudding model of the
atom
what did the discovery of electrons show?
that atoms are not solid spheres and can be divided into smaller parts and have internal structure
why was the alpha scattering experiment carried out
to check if the plum pudding model was correct
how was alpha scattering experiment carried out?
1 alpha particles ( w/ positive charge) fired at piece of gold foil -few atoms thick
2 expected particles to travel through foil
3 some alpha particles bounced back / some deflected
why were particles deflected, bounced back , go straight through
alpha particles with + charge repelled by + charge in centre of atom
bounced back, directly striked nucleus
straight through, went through empty space
most of the particles went through foil- what did this show…..
some particles deflected showed…
most of atom is empty space
centre of atom has + charge
what model replaces the plum pudding model
the nuclear model
what conclusion did the results from the Alpha scattering experiment lead to ?
3 points
. the mass of an atom and + charge is concentrated at the centre
(nucleus)
. atom mainly empty space
describe nuclear model
most of atom is empty
positive nucleus
cloud of electron surround nucleus
how was the nuclear model adjusted
electrons orbit the nucleus at specific distances
who adjusted the nuclear model
Neil Bohr
Bohr said electrons orbit at fixed distances. why was this accepted
his work agreed with the results of experiments by other scientists
how was the electron shell (bohr) model different to the nuclear model
it showed electrons orbiting in shells, fixed energy levels
what was discovered after energy shells
the proton
Further experiments provided evidence that the ……….. contained …… particles called ……..
Further experiments provided evidence that the nucleus contained smaller particles called protons
who discovered neutrons in the nucleus
James chadwick
The experimental work of……. ……….. provided the evidence
to show the existence of …… within the nucleus. This was
about … ….years after the nucleus became an accepted scientific
idea.
The experimental work of James Chadwick provided the evidence
to show the existence of neutrons within the nucleus. This was
about 20 years after the nucleus became an accepted scientific
idea.
why do atoms have no overall charge
same number of protons and electrons
charges of:
electron
proton
neutron
electron -1
proton +1
neutron 0
what is the atomic number
number of protons
All atoms of a particular element have …… number of
protons
. All atoms of a particular element have the same number of
protons
radius of an atom
0.1 nm
(1 x 10 to ^-10 m)
radius of atom in metres
1 x 10 to the power of -10 metres
radius of nucleus
less than 1/ 10 000 of atoms radius
1x 10 to the power of -14 metres
mass of
electron
proton
neutron
electron very small
proton 1
neutron 1
what is mass number
sum of Protons and Neutrons
which number is mass/ atomic number?
23 Na 11
atomic = 11
smaller number
mass= 23
larger number
is atomic number the smaller or larger number
smaller
to work out neutrons…
mass number- atomic number
what is an isotope
atom of same element with different neutron number
what are ions
atom with an overall charge
lost or gained electrons
The relative atomic mass of an element is an…………value that
takes account of the…….. of the……. of the element
The relative atomic mass of an element is an average value that
takes account of the abundance of the isotopes of the element
what does a different mass number mean
different neutron number
equation for relative atomic mass
(mass of isotope1 x % of isotope 1)
+
(mass of isotope2 x % of isotope 2)
divided by 100
how many electrons in each shell
2
8
8
18
what does the outer electron number tell you about element in the table
group number
The elements in the periodic table are arranged in order of ………. number
The elements in the periodic table are arranged in order of atomic
(proton) number
why is it called periodic table
elements with similiar properties occur at regular intervals
group 1 consists of?
highly reactive metals
eg lithium
sodium
potassium
group 7 consist of ?
highly reactive non metals
fluorine
chlorine
bromine
why do elements in same group have similar chemical properties?
because Elements in the same group in the periodic table have the same number of electrons in their outer shell
Before the discovery of protons, neutrons and electrons,how were elements arranged
in order of atomic weights
problems of earlier periodic tables x 2
incomplete
some elements placed in inappropriate groups if strict order of atomic weights followed.
what did mandeleev arrange periodic table by
increasing atomic weight
Mendeleev overcame some of the problems by…..
leaving gaps for undiscovered elements
sometimes changed the order based on atomic weights
why did mandeleev switch the order of specific elemts
so they fitted the pattern of other elements in the same group
what was surprising about madeleevs periodic table- why was table accepted
mandeleev predicted properties of undiscovered elements
Elements with these properties were discovered and filled the gaps.
differences between mandeleevs table and modern one
modern- arranged by atomic number (protons)
modern- has group 0 (not all discovered when madeleev made his table).
why was ordering by atomic weight not always correct
due to isotopes ( different neutron no.)
are noble gases reactive or unreactive
unreactive
why are noble gases unreactive
They are unreactive and do not easily form molecules
because their atoms have stable arrangements of electrons.
which noble gas has 2 electrons
helium
what INCREASES down EVERY group
atomic mass
what happens to boiling points down gr 0
b.p increases down group 0
describe the b.p of noble gases
lower than room temp (as they’re gases)
are most of the elements metals or non metals
metals
where are the metals found on the table
to the left and centre
(to remember this- think that most of the world is left handed…)
where are non metals found on periodic table?
right
what groups are highly reactive metals
group 1 and 2
transitional metals are generally more or less reactive than group 1 and 2 metals?
less
describe what happens when a metal reacts- in terms of electrons
why does this happen
what is the end result
lose electrons
to achieve full outer energy level
have electronic structure as noble gas
Elements that react to form ………. ions are metals.
Elements that form ……… ions are non metals
Elements that react to form positive ions are metals.
Elements that do not form positive ions are non-metals.
why do metals form + ions
Metals LOSE electrons
how do you show an element has become an ion
Square brackets
charge on right corner
[ Li ] +
name for group 1 metals
alkali metals
how many outer electrons do group 1 metals have
1
are group 1 metals hard or soft
soft
describe the reaction of group 1 metals with oxygen
react rapidly with oxygen
what happens to reactivity down group 1
reactivity increases down group 1
all group 1 metals react similarly with oxygen. why
because they all have 1 outer electron
complete and balance
Li + O¬2 =
group 1 reacting with oxygen molecule
4Li + O¬2= 2 Li¬2O
1 O needs 2 Li
O¬2 needs 4 Li
2 Li¬2O is produced
what does 1 chlorine molecule
and 1 oxygen molecule contain
chlorine molecule =2 chlorine atoms
oxygen molecule= 2 oxygen atoms
(Cl2, O2)
describe reaction of group 1 metals with chlorine and oxygen
react rapidly
complete and balance
Na + Cl =
group 1 and group 7
2Na + Cl¬2= 2 NaCl
because Cl is diatomic.
we must use 2 Cl so we also use 2 Na
complete and balance
Na + O¬2 =
group 1 and oxygen molecule (group 6)
4Na + O¬2 = 2 Na¬2O
alkali metal + oxygen =
alkali metal + oxygen = metal oxide
alkali metal + chlorine =
alkali metal + chlorine = metal chloride
elements that react to form ……. …….. are metals
positive ions
what is an ion
an atom with a different electron number
a group 1 metal reacts with oxygen in the air
eg
sodium + oxygen. what is formed
sodium oxide
4Li + O2 =
(Li is group 1, O is group 6)
2 Li¬2O
write balanced equation for sodium and one molecule of oxygen
4Na + O2 = 2 Na¬2O
the first 2 applies to all of the elements
what happens when lithium is added to water
x4
reacts rapidly
effervescence-fizzing
gas produced
water turns alkaline
what happens when sodium is added to water
x4 and 1 comparison to other group 1 elements
reacts very rapidly
effervescence
gas produced
water turns alkaline
reacts more rapidly than lithium
what happens when potassium is added to water
x4 and 1 comparison to other group 1 elements
reacts extremely rapidly
effervescence
gas produced
water turns alkaline
reacts more rapidly then lithium and sodium
write word equation for lithium and water
lithium and water= lithium hydroxide and hydrogen
why does the universal indicator in the water turn purple when group 1 elements are added
products of group 1 metal and water = group 1 hydroxide + hydrogen
(eg lithium hydroxide and hydrogen)
a group 1 hydroxide is an alkali
( regardless of what group 1 it is )
why do we see effervescence when a group 1 element is added to water
(products of group 1 metal and water = group 1 hydroxide + hydrogen)
Hydrogen is formed and hydrogen is a gas so we see bubbling
write balanced chemical equation for li + H2O
(could be: Li + H2O = LiOH + H2
but H isn’t balanced
so: )
2Li + 2H¬2O= 2 LiOH + H2
write balanced chemical equation for Na + H2O
2Na + 2H2O= 2NaOH + H2
write balanced chemical equation for K + H2O
2K + 2H2O= 2KOH + H2
what are the products made when the first 3 group 1 metals are added to water
lithium hydroxide and hydrogen
sodium hydroxide and hydrogen
potassium hydroxide and hydrogen
name first three group 1 elements going down the group
lithium
sodium
potassium
down group 1 you have:
lithium
sodium
potassium
what can you say about the size of these atoms going down the group
size of atoms increase down group, they have increasing electron number
why does reactivity increase down group 1
5 points
-down group, size of atom increases
-there is greater distance btwn + nucleus and -outer electron
- outer electron also shielded from nucleus by internal energy levels
-this means outer electron less attracted to nucleus
- so outer electron easier to lose and element is more reactive
what are group 7 elements called
halogens
if 2 group 7 elements are reacted together they will form….
a molecule with 2 atoms joined by a covalent bond
describe how a covalent bond is made when 2 group 7 elements react together
they overlap their outer energy levels
then
share a pair of electrons
F-F is a covalent bond
what has been formed
fluorine molecule
what elements are diatomic
group 7
oxygen
hydrogen
nitrogen
what happens to melting point and boiling point and relative molecular mass of group 7 elements down group
increases down group
what is room temp
20 degrees
bromine is a liquid at room temp
relate this to its melting and boiling points
bromine melting point is below 20 degrees
but bromine boiling point is above 20 degrees
fluorine and chlorine are gas at room temp
relate this to their boiling point
their boiling point is lower than 20 degrees
iodine is a solid at room temp
relate this to its melting point and boiling point
iodine’s melting & boiling point is higher than 20*
the RMM increases down group 7
(relative molecular mass)
explain what this means in 5 words
molecules get bigger down group
are halogens metals or non metals
non metals
what kind of bond would atoms of the same group 7 elements form together. eg 2 fluorine atoms.
a single covalent bond
what do group 7 elements form when they react with OTHER NON -metal atoms
covalent compounds
in fractional distillation , what might we have to do if liquids have similar boiling points
carry out several rounds of fractional distillation
why do gr 7 atoms from covalent compounds with other non metal atoms
covalent- because as the atoms are non-metal, they each want to gain electrons
compound- because its atoms of Different element chemically joined
halogen + non metal atom=
eg chlorine and hydrogen
covalent compound
eg hydrogen chloride
what do group 7 elements form when they react with metals
ionic compounds
Li + Cl =
(gr1 metal) (gr7 non-metal)
what ions are formed
Cl-
Li+
how do you remember that gr 7 reacting with a metal = ionic compounds
it would be ionic because its a bond between a metal and non metal
and a compound because its 2 different elements
when halogens form 1-ions, how do their names change.
give an example
the -ine turns into -ide
eg fluorine turns to fluoride
what happens to reactivity down group 7
reactivity decreases down group 7
describe what the relative atomic mass is in your own words.
you can use the example of chlorine
isotopes of chlorine have different mass numbers (they have a different neutron number so their weight changes)
there are two main isotopes of chlorine. they have a weight of 35 and 37
to decide what mass number of chlorine should go on the table, scientists worked out the relative atomic mass by using the equation.
they took into account how common each isotope is (the abundance)
what is the negative electron attracted to
the + charge of the nucleus
what happens to the halogens when they react with metals
they gain an electron
why does reactivity decrease down group 7 halogens
5 points
further down the group:
-greater distance between outer energy level and nucleus
-more internal electrons shield the outer energy electrons from positive charged nucleus
-less attraction between outer electrons and nucleus
-harder for elements lower down to attract an electron to its outer energy level
-so they are less reactive than elements higher in group 7
what happens when:
sodium bromide + fluorine
fluorine more reactive than bromine
fluorine can push out the bromine-
a displacement reaction happens
complete word equation
sodium bromide + fluorine =
- fluorine is the first element in group 7
-bromine is the third element in group 7
sodium fluoride + bromine
A more reactive halogen can displace a less reactive halogen from
an aqueous solution of its salt.
give example of ‘an aqueous solution of its salt’ for different group 7 elements
fluorine
chlorine
bromine
iodine
astatine
sodium fluoride
sodium chloride
sodium bromide
sodium iodide
potassium iodide + chlorine =
group 7 elements down the column:
fluorine
chlorine
bromine
iodine
astatine
potassium chloride + iodine
- chlorine is more reactive then iodine so it displaces iodine*
A more reactive halogen can displace a less reactive halogen from what
aqueous solution of its salt.
what have we done to make sodium bromide an aqueous solution
dissolved it in water
where on the table are nonmetals found
right hand side
here are transitional metals found on table
central part
5 main properties of alkali metals
soft
low melting point
low density
react rapidly
form +1 ion
name three substances alkali metals react very rapidly with
oxygen
chlorine
water
what group are alkali metals
group 1
7 properties of transition metals
hard+ strong
high melting points
high density
less reactive than group 1
form ions with different charges
form coloured compounds
can be used as catalysts
where in the table are metals found
left hand side
lithium chloride + bromine=
group 7 elements down the column:
fluorine
chlorine
bromine
iodine
astatine
lithium chloride+ bromine
*bromine is less reactive than chlorine so it doesn’t displace *
give an example of a transition element that can form a coloured compound and the colour
iron (lll) oxide - red
manganese (ll) chloride - pink
chromium (lll) chloride - purple
compare the properties of group 1 alkali metals and transition metals
7 points
ALKALI’S:
soft
low melting point
low density
react rapidly
form +1 ion
TRANSITION METALS:
hard/strong
high melting point
high density
less reactive
form ions with different charges
-coloured compounds
-used as catalysts
what ionic charges can iron form
Fe 2+
Fe 3+
