3.2 Inorganic Chemistry: .1 Periodicity Flashcards
what is meant by periodicity?
trends that occur (in physical and chemical properties) as you move across the periods.
what is the trend in atomic radius as you go across the period?
-as the number of protons increases , the positive charge of the nucleus increases. This means that the electrons are pulled closer to the nucleus, making the atomic radius smaller.
why does the extra electrons that the elements gain across a period not affect the atomic radius?
-the extra electrons that the elements gain across a period are added to the outer energy level -so they don’t really provide any extra shielding effect
what is the trend in atomic radius as you down the group?
-as you go down the group the atomic radius increases down the group -the atoms of each element have one extra complete main level of electrons compared with the one before
what is the trend in melting point as you go across a period 3 metals ?
-the melting points and boiling points increase from sodium and aluminium -because the strength of the metallic bond increases. -this is due to the fact that as you go across the metal ions have an increasing positive charge, an increasing number of delocalised electrons and decreasing radius
why does sodium have a higher melting point than magnesium?
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in the trend in melting and boiling points of the period 3 elements why does silicon have a high melting and boiling point?
-silicon is macromolecular with a tetrahedral structure -strong covalent bonds link all the atoms together -a lot of energy is needed to break these bonds -so silicon has a high melting point
in the trend in melting and boiling points of the period 3 elements why are the melting and boiling points of P, S and Cl low? why does sulphur have the highest melting/boiling point out of these 3 elements?
-P, S, Cl all have simple covalent (molecular) structures -there melting points are due to the strength of the Van der Waals forces between the molecules. -Van der Waals forces are weak and easily overcome so these elements have low melting points. Sulphur is the biggest molecule (S8) so its got a highest melting point
explain why phosphorus has a higher melting point than Chlorine?
-The phosphorus molecule contains P4 molecule -whilst the Chlorine molecule has the Cl2 molecule -therefore Phosphorus is bigger molecule than Chlorine -more atoms in a molecule mean stronger Van der Waal forces -Phosphorus has stronger Van der Waal forces than Chlorine molecule -so more energy is required to overcome the Van der Waal forces -hence the a higher melting point is needed
out of P, S, Cl and Ar why does argon have the lowest melting point?
-argon is molecules are just single argon atoms -it is monatomic -resulting in very week Van der Waals -that don’t need a lot of energy to overcome
which block is Sodium in?
the s-block
which block is rhodium in?
the d-block
which block is iodine in?
the p-block
which block is Curium in?
the f-block
what do you call the elements in group 1?
the alkali metals
what do you call the elements in group 2?
the alkaline earth metals
what do you call the element in the d-block
the transition metals
what do you call the elements in group 7?
the halogens
what is meant by first ionisation energy and give the equation for the first ionisation energy of Mg?
-the first ionisation energy is the energy required to convert a mole of a gaseous atoms into a mole of single positively charged gaseous ions (the energy required to remove one electron from each atom) -Mg (g) –> M+ (g) +e-(g)
what is the general trend in ionisation energy as you go across a period?
the first ionisation energy generally increases across a period
why does the first ionisation energy increase across a period?
- as you go across a period from left to right the number of protons in the nucleus increases,
- which means a stronger nuclear attraction
- all the extra electrons are at roughly the same energy level even if the outer electrons are in different orbital types
- this means theres a generally little extra shielding effect or extra distance to lessen the attraction from the nucleus
what is the pattern for the increase in ionisation energy across a period
2,3,3
why does the ionisation energy drop between phosphorus and Sulphur?
- if you look at the electron congiuration of phosporus you will see that it has 3 electrons in the p sub shell (orbitals) whlist sulphur has one more electron so it must pair up in the p orbital
- this means in sulphur there is spin pairing in the p orbital
- this paired up electrons have a greater repulsion which means that not as much energy is required to remove the outer electron
- hence a decrease in ionisaition energy
why is there a drop in ionisation in period 3 for aluminium?
-the shielding is identical in these elements so it does not a factor in ionisaition energy
if you look at the electron configuration for magnesium and aluminium you will see that aluminium’s outer electron is in a 3p orbital rather than a 3s.
-the 3p has a slighly higher energy than the 3s orbital mean not as much energy is required to remove the electron and is further away from the nucleus which means that the
what is the general trend for ionisation energy down a group?
it generally decreases down a group
why does the ionisation energy generally decrease down a group?
- as you go down the group the amount of shells in each atom increases
- this means that the outer electron is more shielded from the nucleus
- this means that the nuclear attraction is weaker
- meaning that less energy is required to take the outer electron from the atom
the values 906, 1763, 14 855 and 21 013 kJ mol-1 are the first 4 successive ionisaiton energies of an element
state which group this element is in and why
this element is in group 2 because the big jump occurs after two electrons have been removed.
