Topic 4 - inorganic Flashcards
(85 cards)
Why are group 1 metals stored in oil?
When freshly cut they are quite shiny but they rapidly tarnish by reaction with oxygen to form a oxide layer which is why they are kept in oil
How do the flame test colours work?
Electrons are promoted to higher quantum levels via collisions with the high thermal kinetic energy particles. When the promoted electron falls back to its more stable electronic level, energy is emitted. If the wavelength of the photons emitted is in the visible region of the electromagnetic spectrum a ‘flame colour results’.
Explain the ionisation trend down groups 1 and 2?
As you go down the atomic radius increases. Therefore the outer electrons are further from the nucleus and also have more shielding. Therefore less energy is required to remove them
Explain the trends in successive ionisation energies in groups 1 and 2 ?
Successive ionisation energies always increase as the same nuclear charge is attracting fewer electrons and on average closer to the nucleus. The negative electrons are being successively removed from an increasingly more positive ion so more energy is required.
Explain the reactivity trend in groups 1 and 2?
The metal gets more reactive going down the group because it is easier to lose an electrons as the atomic radius increases and the shielding increases therefore the outer electrons are further away from the nucleus.
Explain the melting and boiling points down groups 1 and 2?
Decrease.This is because the ionic radii increase down the group increasing the charge separations between metal cations of the lattice and the free delocalised electrons. This weakens the attractive force and less energy is needed to break these bonds.
Explain the trends in electronegativity in group 1 and 2 elements?
The electronegativity decreases. They get lower because the effective nuclear attractive force on the outer electron charge decreases down the group.
Explain the reactions of group 1 metals with oxygen?
4M + O2 —> 2M2O
It’s a redox reaction and simple oxide is formed.
Write the equation how oxide are soluble in water?
The oxides are soluble in water and form a strongly alkaline hydroxide (except for lithium)
M20 + H2O —> 2MOH
Explain the trend in reactivity of group 2 metals with water?
Becomes more reactive as you go down the group.
Exceptions - beryllium has a strong resistant layer of oxide on its surface which lowers its reactivity at ordinary temperatures.
Summarise the reason for the increase in reactivity of group 2 metals with water?
The reactions becomes easier as the energy needed to form positive ions falls. This mainly due to a decrease in ionisation energy as you go down the group. This leads to lower activation energies and therefore faster reactions.
Explain the strength for group 1 hydroxides as you go down the group?
Strong base getting stronger down the group
Write the reaction for group 2 metals with water?
X + 2H2O —> X(OH)2 + H2
Write the equation for the reaction between Group 1 and water ?
2X + 2H2O —-> 2XOH + H2
Summarise the reason for the increase in the reactivity between group 1 elements and water ?
The reactions become easier as the energy needed to form positive ions falls. This is in part due to the decrease in ionisation energy as you go down the group and also in part to a fall in atomisation energy reflecting weaker metallic bonds as you go down from lithium to caesium. This leads to lower activation energies and therefore faster reactions.
Write the equation for Group 2 metals with oxygen?
2X + O2 —> 2XO
Why do some group 2 metals form peroxides on heating in oxygen?
Peroxide ion - O2 2-
The covalent bond between two oxygen atoms is relatively weak.
If you bring a small 2+ ion close to the peroxide ion. Electrons in the peroxide ion will be strongly attracted towards the positive ion. This forms a simple oxide if the positive ion is small and highly charged - it has a high charge density.
However as you go down the group the positive ions get bigger, they don’t have so much effect on the peroxide ion.
how do group 2 metals form nitrides on heating in air?
Even though nitrogen is thought to be fairly unreactive , all these metals combine with it to produce nitrides, X3N2 containing X 2+ and N 3- ions
Why are different oxides formed as you go down the group?
- lithium form simple oxides
- sodium form peroxide
- potassium, rubidium and caesium form superoxide
Write the equation for the reaction of group 2 metals (not Be) with halogens? (A redox reaction)
M + Cl2 —> MCl2
What happens when magnesium reacts with steam?
It rapidly forms magnesium oxide and hydrogen gas in a vigorous reaction
What’s the test for carbon dioxide?
Limewater is used to test for carbon dioxide - it goes milky as a white precipitate forms.
Write the equation for the reaction of group 2 elements with dilute hydrochloric acid?
X + 2HCl ——> XCl2 + H2
What happens in a between group 2 elements and dilute HCl?
All the metals react with dilute hydrochloric acid to give bubbles of hydrogen and a colourless solution of metal chloride.
Reaction get more vigorous down the group.