Periodicity Flashcards
What are elements in the periodic table ordered by?
Their proton number.
What do elements in the same group have?
The same number of electrons in their outer shell and similar properties.
What happens to the atomic radius as you go acros a period?
It decreases.
Why does the atomic radius increase as you go across a period?
There is an increased nucear charge as there is an increased number of protons, this means that the outer shel of electrons are further pulled into the nucleus.
Why does the shielding of an element stay similar across a period?
All of the extra atoms gained across this period go into the same shell.
Why is there a general increase in melting points in the first three elements of period three?
They all have metallic bonding as they are all metals, due to the increase in positive charge across a period the delocalised electron number also increases. This causes a smaller ionic radius and means a stronger metallic bond.
Why does silicon have the highest melting point in period three?
It has a giant covalent structure meaning that many strong covalent bonds are holding the silicon atoms together and therefore a large amout of energy is needed to overcome these strong covalent bonds.
Why does phosphorus have a lower melting point than silicon?
It has a weaker and simpler molecular structure and the melting point is determined by weaker van der waals forces.
Why does sulfur have a higher melting point than phosphorus?
It has a larger simple molecular structure meaning that is has larger van der waals forces and hence has a higher melting point.
Why does chlorine have a lower melting point than sulfur?
It has a smaller simple molecular structure meaning it has smaller vand er waals forces and hence a lower melting point.
Why does argon have a lower melting point than the rest of period three?
It only exists as indiviual atoms and it has smaller van der waals forces and hence a lower melting point.
What is ionisation energy?
The minimum amount of energy required to remove one mole of electrons from one mole of atoms in the gaseous state.
Why is ionisation always an endothermic process?
Ionisation requires energy.
Why is ionisation energy lower for larger atoms?
The bigger the atom the further away the outer electrons are from the nucleus. The attractive force between the nucleus and outer electrons reduces making it easier to remove electrons.
What is sucessive ionisation?
The removal of more than one electron from the same atom.
