Chapter 8 - Reactivity trends Flashcards
What is common about all elements in group 2?
They are all reactive metals which form 2+ ions
Why are group 2 elements called reducing agents?
In a redox reaction, they lose electrons (oxidation) which is donated to the other reactant, reducing it
What is the most common type of reaction for group 2 elements?
Redox
What happens when a group 2 metal reacts with oxygen?
It forms a metal oxide with the general formula MO
What is produced when a group 2 metal burns in oxygen?
A solid, white oxide
What is produced when group 2 metals react with water?
An alkaline metal hydroxide and hydrogen gas
What is the general formula for group 2 metal hydroxides?
M(OH)2
What is produced when group 2 metals react with dilute acid?
Metal + Acid -> Salt + Hydrogen
Why does reactivity increase down group 2?
Group 2 metals wish to lose 2 electrons from their outer shell, to gain a full outer shell. Ionisation energy decreases down the group, because of an increase in atomic radius and there are more electrons to shield
Why do the first and second ionisation energies decrease down group 2?
Increasing atomic radius and the shielding effect of other electrons means less energy is needed to overcome the force
What happens when an oxide of a group 2 metal reacts with water?
Metal hydroxides are formed which dissolve to form hydroxide ions (OH-) and alkaline solutions of the metal hydroxide (ions)
Why is slaked lime (Ca(OH)2) often spread onto fields?
It is a base and neutralises acidic soils so crops can grow
Why are group 2 bases, like Mg(OH)2 and CaCO3 used as antacids?
The bases neutralise the hydrochloric acid in your stomach which is causing the discomfort
Ionic equation for neutralisation
H+ (aq) + OH- (aq) -> H2) (l)
What happens when a solution of group 2 hydroxides becomes saturated?
Any metal and hydroxide ions will form a solid precipitate
Because the solubility of group 2 hydroxides increases down the group, what happens to the resulting solution?
They contain more OH- ions and are more alkaline
How to show the increasing alkalinity of group 2 hydroxides?
Add a spatula of metal oxide to some water and shake
Measure the pH. This will increase down the group
Why do the group 7 elements not occur in their elemental forms in nature?
They are highly reactive
At RTP, what will all halogens exist as?
Diatomic molecules (two atoms joined by a single covalent bond)
In their solid states, what will the halogens form lattices with?
Simple molecular structures
Colour and state of fluorine
Pale yellow, gas
Colour and state of chlorine
Green, gas
Colour and state of bromine
Red-brown, liquid
Colour and state of iodine
Grey, solid