Chapter 8 Flashcards
Why are group 2 elements reducing agents?
Because they lose their outer S2 electrons to form 2+ ions.
What is happens to reactivity of group 2 elements.
Reactivity increases down the group.
Which group 2 metals react with oxygen and to form what?
All group 2 metals react with oxygen to produce metal oxide.
Which group 2 metals react with water and to form what?
Group 2 metals generally react with water to form metal hydroxides and hydrogen.
What redox reactions happen with group 2 elements?
group 2 elements and dilute acid to produce a salt and hydrogen.
What happens to first & second ionisation energy for group 2 elements? why?
It decreases down the group
- the outermost electrons are held more weakly as they are further away from the nucleus - weakens the attraction
- the outer shell/ electrons become more shielded from the attraction of the nucleus by the repulsion force of inner shell electrons
What happens when group 2 elements react with water?
form group 2 metal hydroxides
What is formula of hydroxide for Mg?
Mg(OH)2
What is the trend of metal 2 hydroxides down the group?
- solubility increases down the group, resulting in solutions that contain more OH- ions, hence an increase in alkalinity , ph. also increases from 10 to 12
What three types of group 2 act as bases?
- group 2 hydroxides, carbonates and oxides
What is Ca(OH)2 used for?
It used in agriculture to neutralise acidic soils to help maintain an optimum ph for crops.
What is CacO3 and Mg(OH)2 used for?
Used as an ‘antacid’ to neutralise excess hydrochloric acid during indigestion.
What are group 7 elements known as?
Halogens
Which block of the periodic table is where group 7 elements are?
Part of p-block.
What 4 things increase down group 7?
- nuclear charge
- no. of electrons
- atomic radius
- boiling point
What happens to reactivity down group 7?
Reactivity decreases down the group.
What happens when more electrons are added down the group?
- The strength of the temporary dipoles increases
- Increased dipoles mean greater London forces, leading to an increase in melting and boiling point.
Why are group 7 elements can be oxidising agents?
Because they often gain an electron to form a 1- halide ion.
How do halogens displace each other?
A higher up and more reactive halogen will displace a less reactive halide ion from a solution.
How can you tell a halogen displacement has taken place?
A colour change
What happens to group 7 elements down a group?
Down the group, the increase in atomic radii and shielding outweighs the increase in nuclear charge, so electronegativity decreases.
What happens when electronegativity decrease?
Electronegativity decreases down a group, reduces a halogen’s ability to attract an electron and form a 1- ion, hence it’s reactivity.
What is a disportionation reaction?
Is where a single element is simultaneously reduced and oxidised in a reaction.
Give an example of a disportionation reaction?
Chlorine when added to water. Cl2 + H2O to HCL + HClO
Chlorine 0 then HCl is -1 then HClO is +1
