Periodicity Flashcards
(17 cards)
Explain the first ionisation energy
Energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions
It’s an endothermic process which means energy is required to overcome electrostatic attraction between positive nucleus and negative electron
What are the factors affecting nuclear attraction and therefore ionisation energy
1.Nuclear charge
The more protons there are in a nucleus, the stronger the electrostatic force is between nucleus and electrons. This means more energy is needed for an electron to be removed
2. Atomic radius
Attraction falls off rapidly with distance . An electron closer to the nucleus needs more energy to remove it
3.shielding
As the number of electrons between outer electrons and the nucleus increases the outer electrons feel less nuclear attraction. This is because electrons absorb the nuclear charge.
Why does ionisation energy decrease down the group
Number of shells increases so shielding increases
Atomic radius increases
Nuclear charge increases but is overweighed by atomic radius and shielding
Nuclear attraction for outer electron decreases so electrons more easily lost
Why does ionisation energy increase across a period
Nuclear charge increases
Shielding is similar as the electron is being removed from the same shell
Atomic radius decreases (as the nuclear charge pulls it in and the amount of shells is constant)
And there more nuclear attraction
What’s the exception of ionisation energy between group 2-3
Mg has an outer electron in 3s sub shell and Al has outer electron in 3p subshell
3p sub-shell has higher energy which means that there is shielding and it’s easier to remove electron from 3p subshell rather than 3s because 3s is closer to the nucleus
Increase in shielding outweighs the increase in nuclear charge
What’s the exception of ionisation energy between groups 5-6
The shielding between group 5 and 6 is the same as an electron is being removed from 3p subshell
However group 6 electrons are easier to remove as its beating removed by an orbital (its electrons already have repulsion)
Describe group 2 elements
They are oxidised which means they loose two electrons to form 2+
They act as a reducing agent
What is the trend in reactivity down group 2
-number of shells increase so shielding increases
-atomic radius decreases down the group
-nuclear charge increases down the group but is overweighed by atomic radius and shielding
-nuclear attraction for outer electron decreases so less energy is required to remove electron so reactivity increases
What happens when group 2 metals react in water
Form metal hydroxides and h2 gas
And hydroxides are more soluble down group 2
What happens when group 2 metals reacts with oxygen
They react with oxygen - combustion
They produce a white powder
What happens when a metal oxide reacts with water
They react with water to form metal hydroxides which dissolve to form strong alkaline solutions
Metal oxides increase in reactivity with water down the group resulting metal hydroxide to be more soluble
Stronger alkaline solution means higher pH
Group 2 hydroxides and sulfates
Magnesium sulfate is soluble and magnesium hydroxide is insoluble
Barium sulfate is insoluble and barium hydroxide is soluble
What are the uses of group two compounds
- Ca(OH)2 - used in agriculture to neutralise acidic soils
- Mg(oh)2 and CaCO3 used to neutralise excess stomach acid
- BaSO4 is used In barium metals
What mappers to group 8 elements boiling point down the group
The boiling point increases down the group
Number of electrons and atomic radius increases
Strength of the dipole dipole interactions increase between atoms which requires more energy to overcome
What happens to elements boiling point across a period 3
Na to Al increases as the number of electrons increase and charge on positive ion increases
Metallic bonding gets stronger
From Al to Si it increases as Si has strong Covalent bonds
From P4 to to Ar
- decreases to P4 because its a simple molecular structure with weak induced dipole dipole interactions
It increases to S8 as it is a larger molecule with more electrons with stronger dipole dipole interactions which require ,Moore energy to overcome
Decreases to CL2 as there’s less atoms
Ar is the smallest molecule
Are halogens less reactive or more reactive down the group
-less reactive and oxidising
-atomic radius increases
-outer electrons are further away from the nucleus and are more shielded from the nucleus
-less nuclear attraction so more difficult to attract an electron to form an ion
What are observations from displacement reactions in aqueous solution and with organic solvent
We can shake with an organic convent to make the colour stand out more
A halogen dissolves In an organic solvent which forms a solvent layer that can be separates using a funnel
1. Aqueous solution
(Iodine - brown )(Bromine -orange )(chlorine - pale green)
2. With organic solvent
(Iodine- violet)(bromine-orange)(chlorine- pale green)
