inorganic 1 - periodicity Flashcards
how are elements in the periodic table arranged?
elements are arranged according to their proton number
what is a period on a periodic table?
the horizontal rows
what is a group on the periodic table?
the vertical columns
what are the 4 blocks of the periodic table?
s,p,d,f blocks
what elements are in each block of the periodic table?
s blocks - group 1 and 2
p block - group 3 to 0
d block - transition metal
f block - radioactive element
what is periodicity?
the study of trends within the periodic table
what is the trend in atomic radius along a period?
- along a period, atomic radius decreases
why does atomic radius decrease along a period?
- increases nuclear charge for the same number of electron shells.
-This means the outer electrons are pulled in closer to the nucleus because the charge produces a greater attraction.
what is the trend in atomic radius going down the group?
going down a group, atomic radius increases
why does atomic radius increase going down a group?
- electron shell is added with each element going down the group
- this increases the distance between the outer electrons and the nucleus
-more shells increase the shielding = inner shells become a barrier that blocks the attractive forces - nuclear attraction is reduced further and atomic radius increases
what is the trend in ionisation energy along a period?
- ionisation energy increases
why does ionisation energy increase along a period?
- atomic radius decreases = hence nuclear charge increases
- this means that the outer electrons are held more strongly = more energy is required to remove the outer electron and ionise the atom.
what is the trend in ionisation energy going down a group?
ionisation energy decreases
why does ionisation energy decrease going down a group?
- the nuclear attraction between the nucleus and the outer electrons reduces and the shielding also increases
- this means less energy is required to remove the outer electron
what does the melting point of period 3 elements depend on?
- structure of element
- bond strength
what happens to melting point across period 3, between sodium and aluminium?
-Na,Mg, Al = metals with metallic bonding
Their melting points increase along period 3, due to greater positive charge of their ions.
-The bonds get stronger because the metal ions have an increasing positive charge , increasing number of delocalised electrons and a decreasing radius.
-This increases the attractive electrostatic forces from Na to Al, therefore more energy is needed to break them.
why does the melting point increase dramatically for silicone in period 3?
- silicone has a very strong covalent structure
- a lot of energy is needed to break the strong covalent bonds = giving it a high melting point
why does the melting point decrease in period 3 between phosphorus and chlorine?
Phosphorus, Sulfur and chlorine are all simple covalent molecules held by van der waals forces
less energy is needed to overcome these weak intermolecular forces = so they have low MP.
why does argon have an even lower melting point than chlorine?
- noble gas that exists as individual atoms and full outers hell electrons
- this makes them very stable so VDW forces are very weak
- therefore less energy is needed to overcome these VDW forces = exists as gas at room temperature
why is there a Dip at Al for Ionisation energy?
outer electron is in a 3p orbital, which is higher in energy than 3s. Electron is found further than the nucleus. 3s orbital provides shielding. Less energy is needed to remove the outer electron than Mg
Why is there a dip at S for ionisation energy?
one 3p orbital contains 2 electrons = there is repulsion between paired electrons so less energy needed to remove on.
