C4.1.1 Alkali Metals Flashcards
Why are they called alkali metals
React with water to form alkaline solutions
Properties of group 1 elements
Shiny when freshly cut
Good conductors of heat and electricity
Low melting and boiling points - still solid at room temp
Malleable and ductile
Soft enough to cut with knife - increases down group
Low density
Going down the group…
Density increases (although sodium is denser than expected
Melting point decreases
Reactivity increases
alkali metal + water
Metal hydroxide + hydrogen
What happens when sodium reacts with water
Melts to form a silvery ball, fizzes vigorously and quickly disappears
What happens when potassium reacts with water
Immediately ignites, burns with a lilac flame and very quickly disappears
Why does the density increase going down (except potassium)
The increase in atomic mass is greater/faster than the increase in atomic volume
What happens when lithium reacts with water
Fizzes steadily and slowly disappears
Why do melting points decrease as you go down
As atom size increases due to addition of more electron shells
electrostatic attractions between positive metal ions and delocalised electrons weaken
Requiring less energy to break bonds and resulting in lower melting points
Charge of alkali metals
+1
Why does reactivity increase as you go down
Atom size increases
So, outer electron gets further from the nucleus
So the attraction between the nucleus and the outer electron gets weaker
So the electron is more easily lost
What happens when alkali metals react with oxygen
The form compounds making them dull, coating them.
This is why they are normally kept in oil to prevent this.
As they go down the group, the reaction gets quicker.
What happens when alkali metals react with water?
React vigorously and produce hydrogen gas and a hydroxide of the metal
What happens when alkali metals are exposed to dilute acids
Produce a salt and hydrogen gas
