Group 1 and 7 Flashcards
what are the similarities of the physical properties of Alkali metals?
the melting point is low and it gets lower as you go down the group. The density tends to increase as you go down the group (not regularly). Li, Na, K are all less dense than water. THey are all very soft, getting softer as you go down. THey are shiny when freshly cut but tarnish quickly in air
why does Li, Na, K float on water
because they are less dense than water
how do you prevent any reactions form taking place with Na, Li, K and other alkali metals
by storing them under oil
What happens when alkali metals are put into water? write out the chemical reaction. What changes the speed of the reaction?
They react rapidly and form strong alkaline solutions of metal hydroxides.
2M + 2H2O -> 2MOH + H2 (M being an alkali metal)
As you go down the group, the reaction occurs more rapidly as metals are more reactiv
so if you have enough sweat on your hands a corrosive metal hydroxide will form
what are the similar chemical properties of group 1 metals?
they all react with water to form a hydroxide (with formula MOH), they react with oxygen to form an oxide (with formula M2O), they form with halogens to form compounds with the formula MX e.g., LiCl, they form ionic compounds which contain an M+ ion e.g, Na+
m represents an alkali metal
what do chemical properties depend on?
no. electrons in outer shells
name the main observations that would take place when sodium is put into water
sodium floats (less dense than water),
sodium melts into a ball because it has a low melting point and lots of heat is produced by the reaction,
effervescence/ fizzing (hydrogen gas produced), sodium moves around on the surface of the water because the hydrogen isn’t given off symmetrically,
the piece of sodium gets smaller and eventually disappears (as it is used up),
if you ted the solution with universal indicator it goes blue because an alkaline solution has been formed (metal hydroxide so it contains OH- ions)
what is the difference between the reaction between lithium and sodium
the reaction with lithium is slower because it has a higher melting point, and the heat isn’t produced as quickly so the lithium doesn’t melt
what is the equation of the reaction with water and K, Na, and Li?
2 Na ( s ) + 2 H 2 O ( l ) → 2 NaOH ( aq ) + H2 ( g )
2 K ( s ) + 2 H 2 O ( l ) → 2 KOH ( aq ) + H 2 ( g )
Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g).
what happens when lithiums reacts with water?
reaction is slower than sodium’s
- lithium has a higher melting point
- lithium doesn’t melt
– effervesces more slowly
- takes longer to disappear
- floats and moves around on the water (same reasons as sodium)
what happens when potassium reacts with water?
the fastest reaction overall
- enough heat is produced to ignite the hydrogen, which burns with a lilac flame
- reaction often ends with potassium spitting around and exploding
-effervesces
- moves around the water and floats
fizzes MORE vigorously than sodium, moves around and disappears quicker
what is the reaction with rubidium or caesium and water?
dangerous and explosive
describe the trend of reactivity in group 1
as you go down the group, the ELECTROSTATIC ATTRACTION between the nucleus and outer shells gets weaker (as the distance between the nucleus and outer shell increases aka radius) so it is easier for the atom to lose its electron on its outer shell. Therefore, rwactivity increases as you go down group 1. Shielding also increases as you go down the group which dampens the electrostatic reaction
what happens with a group 1 element in air
it tarnishes, the more reactive, the quicker it tarnishes. It tarnishes to form an oxide with the formula M2O (M being an alkali metal)
what happens if you heat an alkali metal in air using a bunsen burner?
you get a much more vigorous reaction and it is more difficult to tell the reactivity of the metals as the reactions are so rapid.
what happens when Li is heated using a bunsen burner in air?
Li burns with a red flame to form Lithium oxide
what happens when Na is heated using a bunsen burner in air?
Sodium burns in a yellow flame to form sodium oxide
what happens when K is heated using a bunsen burner in air?
it burns with a lilac flame to form potassium oxide?
what is the reaction for a metal alkali reaction in air? what is produced?
4M (g) + O2(g) -> 2M2O (s) (M is an alkali metal)
A WHITE POWDER, AN ALKALI METAL OXIDE, IS PRODUCED
what colour are group 1 metal ions? what does this mean?
colourless, meaning that their compounds will be colourless or white unless they are combined with a coloured negative ion like orange Potassium dichomate (VI)
what are group 1 compounds?
typical ionic solids and mostly soluble in water
if most group 1 compounds are white/colourless, what colour will they dissolve to be?
colorless solutions
