The Alkali Metals Flashcards
(24 cards)
Why are the alkali metals stored in oil?
The alkali metals are stored in oil because they react vigorously with water and oxygen, including the moisture in the air
What happens when alkali metals react with water?
a metal hydroxide if formed
hydrogen gas is given off
What happens when a metal hydroxide dissolves in water?
an alkaline solution is formed
what is formed when alkali metals react with non metals
produce ionic compounds 1+ ions
what is the boiling point and melting point trend of the alkali metals going down the group?
They have low melting and boiling points
Decrease going down the group
Describe the trend in reactivity
The reactivity increases going down the group
Why do the alkali metals increase in reactivity going down the group?
Because number of shells increases and the outer electron get further away from the influence of the nucleus so it can be lost more easily.
What are the properties of the alkali metals?
- soft
- shiny when cut but quickly dull/tarnish with the oxygen in the air
- low m.p and b.p
- very reactive with water
- low densities so float on water
- alkaline solution
describe the reaction between water and lithium
exothermic
fizzes and floats on water
reaction is slower than others
Why does the reactivity of the Alkali Metals increase going down the group?
(Long Answer)
The atoms get larger as you go down, so the single electron in the outermost shell is attracted less strongly to the positive nucleus.
The electrostatic attraction with he nucleus gets weaker because the distance between the outer electron and the nucleus increases.
Also, the outer electron experiences a shielding effect from the inner electrons, reducing the attraction between the oppositely charged outer electron in the nucleus.
The Alkali Metals have a silvery,shiny surface when they are first cut. What happens to metal a few seconds later?
The metal goes dull as it very quickly reacts with the oxygen in the air.
e.g sodium +oxygen ——> sodium oxide
Why do the alkali metals try to lose an electron form their outermost shell?
to become stable
Write a chemical reaction as the alkali metals react with oxygen …use lithium
sodium
potassium
Lithium + oxygen —-> Lithium oxide
4Li O2 2Li2O
4Na + O2—>2Na2O
4K + O2—–>2K2O
What observations can be made as the alkali metal react with oxygen at room temperature and the heated?
At room temperature the colour changes from shiny to grey and dull white (metal oxide coats it)
When heated, they burn vigorously , forming white smoke(metal oxide)
Group 1 oxide can dissolve in water to…
form soluble,colourless solutions alkaline
known as metal hydroxides
Group 1 reactions with halogens -chlorine
2Li + Cl2 —-> 2LiCl
2Na +Cl2 ——> 2NaCl
2K +Cl2 —–> 2KCl
what observations can be made as halogens (e.g chlorine) react with group 1 elements
Very vigorous reaction with bright light and lots oh heat produced
Produces a metal chloride (White Solids) - salts
These dissolve in water to for colourless solutions
what observations can be made as group 1 lents react with water
Very vigorous reactions Fizzing/ bubbles Floats and moves Metal dissolves Solution is alkaline Release enough energy to melt the metal
How how potassium react with water?
Melts into a ball and bests into a lilac flame
this is because it is further down the group and more reactive
reacts more quickly and vigorously
Write a chemical equation for the reactions of the alkali metals and oxygen
2Li +2H2O —–> 2LiOH +H2
2Na +2H2O —-> 2NaOH +H2
2K +2H2O——> 2KOH +H2
Describe the reaction of Lithium with oxygen
Burns with a red flame
Describe the reaction of Lithium and Oxygen
Floats
Releases bubbles of hydrogen
Describe the reaction of sodium with Oxygen
Burns with a yellow/orange flame
Describe the reaction of Potassium as it reacts with Oxygen
Burns with a lilac flame
