periodic table Flashcards
4key differences between mendelelv’s table and the modern periodic table
- modern table odered by atomic number not atomic mass like mendeelev’s
- no group 8 in medeelev’s table because those elements were discovered later
- transition metals in the modern table
- contained ~50 elements, modern contains 118
how did mendeleev arrange the elements in his periodic table?
- arranged ~50 kown elements based on their properties
- in order of atomic mass, groups with similar chemical properties were in columns
- switched some to keep with pattern since some of his RAMs were wrong due to prescence of isotopes
- left gaps for undiscovered elements, and preticted their properties
how did the discovery of gallium prove mendeleev’s table was correct?
- left a gap for gallium and predicted its chemical and physical properties based on surrounding elements’ properties
- his predictions were correct, proving his table was correct too
how is the modern periodic table arranged?
- asceding atomic number left to right
- groups (vertical columns) with similar chemical properties due to same number of electrons in outer shell
- periods (horizontal rows) with sam number of shell
what separates metals and non-metals on the periodic table?
‘stairway to boron’
(B, Si, As, Te, At)
general properties of metals
- high melting and boiling points
- all solids except mercury
- malleable
- good conductors of heat and electricity
- ductile
- usually ‘shiny’
general properties of non-metals
- usually lower boiling and melting points than metals
- brittle
- poor conductors of heat and electricity (except graphite)
which group has the most reactive metals and why?
group 1 - alkali metals
only need to lose 1 electron to get a full outer shell
which group has the most reactive non-metals and why?
group 7 - halogens
just need to gain 1 electron to get full outer shell
which group is unreactive and why?
group 8/0 - noble gases
already have full outer shells
what are properties of alkali metals?
- soft (can all be cut with a knife)
- low densities
-relitavely low melting and boiling points
how does the melting point of alkali metals change a you go down the group and why?
- melting point decreases
- weaker metalic bonds which need less energy to overcome because thety are bigger ions with more shells
how does lithium react with water?
2Li(s) + 2H20 (g) -> 2LiOH (aq) + H2(g)
- move around the surface of water
- lots of fizzing (hydrogen gas)
- solution becomes alkaline due to lithium hydroxide produced
how does sodium react with water?
2Na(s) + 2H20(g) ->2NaOH(aq) +H2(g)
- move around the surface of water
- more fizzing than lithium (hydrogen gas)
- melts due to heat of reaction
- solution becomes alkaline due to sodium hydroxide produced
how does potassium react with water?
2K(s) + 2H20(g) ->2KOH(aq) +H2(g)
- move around the surface of water
- more fizzing than potassium ad lithium (hydrogen gas)
- sets on fire (lilac flame)
- melts due to heat of reaction
- solution becomes alkaline due to sodium hydroxide produced
how do rubidum and caesium react with water?
explode on contact with water
(react very vigourosly)
as you move down group 1, … (3)
- reactivity increases
- boiling points and melting points decrease
- densities increase
why does reactivity increase as you go down group 1?
- the easier it is for an atom to lose its outer electron, the more reactive it is
- the nearer the outer electron is to the nucleus the more difficult it is for the atom to lose it because it is more strongly attracted by the positive nucleus
- as you go down group 1, number of shells (so the distance between the nucleus and the outer electron) increases so the nucleus’ force of attraction is weakier making it easier for the atom to be lost SO IT IS MORE REACTIVE
what common properties do all group 1 compounds have?
- all ionic
- all white
- soluable
- all solutions of compounds are colourless
what are 4 common properties of halogens (group 7) ?
- all diatomic molecules
- react with metals to form ionic compounds (salts)
- react with water to form acidic solutions
- react with hydrogen to form hydrogen halides
what colour and state is flourine at room temp?
yellow gas
what colour and state is chlorine at room temp?
green gas
what colour and state is bromine at room temp?
red/brown liquid
what colour and state iodine at room temp?
dark grey solid
as you go down group 7,…. (3)
- reactivity decreases
- density increases
- boiling and meltig points increase due to greater inter-molecular forces between molecules
what is the chemical test for chlorine?
bleaches damp litmus paper
(blue > red > white)
how and why does reactivity change as you go down group 7 (halogens)?
the easier it is for an atom to attract an electron to fill its outer shell, the more reactive it is
- the nearer the other atom’s outer electron is to the nucleus the easier it is for the atom to gain it because it is more strongly attracted by the positive nucleus
- as you go down group 7, number of shells (so the distance between the nucleus and the outer electron) increases so the nucleus’ force of attraction is weakier making it more difficult for the atom to gain the electron SO IT IS LESS REACTIVE AS YOU GO DOWN THE HALOGENS
what happens in displacement reactions?
a more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt
what type of reaction are displacement reactions?
redox reactions
(reactions where both oxidation and reduction occur)
what does OILRIG mean?
oxidation
is
loss (of electrons)
reduction
is
gain (of electrons)
how do hydrogen halides react with water?
dissolve to make acidic solutions
how can displacement reactions show halogens’ reactivity?
more reactive displaces less reactive
- chlorine displaces both bromine and iodine
- bromine can’t diplace chlorine, but can displace iodine
- iodine cannot displace bromine or chlorine
how are hydrogen halides formed?
hydrogen + halogen
(colourless gas)
why are noble gases inert (unreactive) ?
- already have full outer shells
what are noble gases?
- unreactive
- monatomic (exist as single atoms)
- group 8/0
- all gases at room temp
what are the properties of noble gases?
-low boilig points (all gases at room temp
- low densities/particles spread out
what changes as you move down group 8 and why? (2)
- boiling point increases (weak forces between the atoms increases as the atoms get bigger/more shells)
- densities increase (larger and heavier)
what is a use of helium?
low density >
party balloons
what is a use of xenon?
sun/tan beds
what is a use of neon?
when electric current is passed through a tube of neon under low pressyre, coloured light is produced > used for coloured lights/ advertising signs
why can noble gases eg argon be used in welding?
- prevent the hot metal from reacting with oxygen
what are the properties of transition metals?
- ductlie, malleable, good conductors, strong like other metals
- form coloured compounds
- form multiple types of ions eg iron (II) and iron (III)
- high densities
- high melting points
- don’t react with water or air as much as other metals
what colour are copper compounds?
blue
what colour are iron (II) compounds?
pale green
what colour are iron (III) compounds?
orange/brown
what colour are nickel compounds?
green
what are alloys?
metals with another element (can be metal or non-metal) added
eg stainless steel is an alloy of iron
why are alloys stronger than pure metals?
- atoms are not all the same size so the added atoms will disrupt the layers of the pure metal
- this will make it more difficult for the layers to slide over each other and make the alloy not malleable, so stronger
