Unit 4 - Alkali Metals And Alkaline Earth Metals Flashcards
Sodium with water reaction
When sodium is added to water, the sodium melts to form a ball that moves around on the surface. It fizzes rapidly, and the hydrogen produced may burn with an orange flame before the sodium disappears.
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
Potassium with water
When potassium is added to water, the metal melts and floats. It moves around very quickly on the surface of the water. The hydrogen ignites instantly. The metal is also set on fire, with sparks and a lilac flame. There is sometimes a small explosion at the end of the reaction.
2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)
Group 1 are also know as
The alkali metals
Group 2 is the
Alkali earth metals
Reactivity of elements in group 1 in terms of distance between the outer electrons and the nucleus
Group one elements are more reactive further down the group.
They need to loose the one electron on the outer shell to react. Electrons are held to an atom by the protons in the nucleus. If an electron is close to the nucleus the force holding it in will be very strong, if it is further away it will be weaker.
So bigger atoms (towards the bottom of the group) with the outer orbital far from the nucleus will loose their electron more easily: this means they react more vigorously.
Smaller atoms with the electron closer to the pull of the nucleus (at the top of group one) will be less reactive as it takes more to lose the electron.
What colour does Li+ give in a flame test
Carmine red
What colour does Na+ give in a flame test
Yellow
What colour does K+ give in a flame test
Lilac
What colour does Ca++ give in a flame test
Orange
Lithium and water reaction
When lithium is added to water, lithium floats. It fizzes steadily and becomes smaller, until it eventually disappears.
2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)
