1.6 periodic table flashcards
(30 cards)
definition of an element
a substance that contains only one type of atom and cannot be broken down into anything chemically simple
Mendeleev and the periodic table
Russian scientist, Demetri Mendeleev in 1869, his key to success was realization that previous attempts had failed because a number of elements were as yet undiscovered and that gaps must be left for such elements in the classification
he wrote down what he knew about each element on a separate card then sorted card into piles brining together elements which had features in common. Then he laid out cards in rows, in order of atomic mass
he noticed he needed to start a new row with every 8th element. in each row there was a pattern in properties of element from the metal to the non metal , Mendeleev called this periodic variation in the properties and that is how the table got its name
what is the fundamental difference between the modern periodic table and Mendeleev’s
Mendeleev arranged the elements in order of increasing atomic mass. Modern table in order of increasing atomic number
other key differences between modern periodic table and Mendeleev’s
more elements/ no gaps in modern periodic table
separate block for transition metals in the modern periodic table
noble gases have been discovered and are present in the modern periodic table
Actinides and lanthanides are present in the modern periodic table
metals
good conductors of heat and electricity
ductile
malleable
high melting point
sonorous
( due to the delocalized electrons the layers of ions can slide over each other and rearrange without breaking the metallic bond)
non metals
poor conductors of heat and electricity
brittle when solid
low melting points
non sonorous
Group 0
monatomic they are on their own and don’t mix with any other elements, so they exist as separate single atoms
they are a group of very unreactive non metals- it was 1963 before anyone managed to get any of these elements to take place in a chemical reaction
they are very hard to detect as they are chemically inert
they are all colorless gases at room temperature
boiling points increase down group 0
They have a full electronic structure which means that they are stable
Group 1
reactivity increases down group 1
they react very quickly with oxygen. That is why, when the metals are freshly cut, they are shiny but tarnish quickly and lose their metallic luster
they are stored in oil to prevent them reacting with oxygen and moisture in the air
why are group 1 elements called alkali metals
Alkali metals+ water> metal hydroxide + hydrogen
because they react with water to produce a hydrogen gas and an alkaline solution
How are alkalis prepared for their reaction with water
residue oil from the storage vessel is removed from the surface using filter paper. Due to the heat of the reaction, the oil can burn and release a choking smoke.
safety precautions required when alkali metals are reacted with water
small piece of metal
large through of water
gloves and safety goggles
tongs to lift metal
safety screen
lithium observations
floats on surface
moves about on surface
fizzes/ gas given off
solid eventually disappears
heat is released
colorless solution formed
sodium observation
all the same as lithium
except melts into a silvery ball
potassium
all the same as lithium
burns with a lilac flame
small explosion/ crackle
properties of alkalis that are unusual
soft, easily cut with a knife and expose a shiny surface
shiny surfaces quickly tarnish in air
float in water: less dense in water
react vigorously with water
why do all alkali metals have similar properties
when alkalis react they need to lose their one outer shell electron to obtain a full outer shell and form 1+ ions as a result. explaining why all alkali metals have similar properties and it can be shown by an ionic equation.
OXIDATION
gain of oxygen
loss of electrons
loss of hydrogen
Reduction
loss of oxygen
gain of electrons
gain of hydrogen
As we go down group 1 the trend of reactivity increases
the outer electron is getting further away from the attractive pull of the nucleus
there are more inner shell electrons which shield the outer electron from the attractive pull of the nucleus
hence the outer electron is more easily lost
and the elements become more reactive.
Group 7 halogens
this a group of reactive non metals
the halogens are toxic
they all exist as diatomic molecules
reactivity decreases going down the group
group 7 elements physical states
fluorine- F2- yellow gas
Chlorine-Cl2- yellow-green gas
Bromine- Red-brown liquid
Iodine-I2- Grey black solid
Astatine- black solid
melting and boiling points increase going down the group resulting in a change of state from gas to liquid to solid
this is because the weak forces that exist between the diatomic molecules increase as the molecules get bigger, meaning more energy is needed to overcome these forces so the melting point and boiling point increases
Iodine sublimation
Sublimation- change of state from solid to gas on heating
Iodine gas is purple and the grey black solid iodine sublimes to form a purple gas when heated
Test for chlorine gas
Damp universal PAPER changes to red and then bleaches white
As we go down reactivity decreases
the group 7 elements all have similar chemical properties because when they react, the atoms need to gain one electron in order to obtain a full outer shell and they form 1- ions as a result
