periodicity Flashcards
how are the elements arranged in the periodic table
arranged by proton number
what are groups and periods
group- down and have same number of electrons in outer shell
periods - across and have same b=number of electron shells
atomic radii across a period
decreases- increased nuclear charge as there is an increasing number of protons pulls the outer shell of electrons further in towards nucleus
melting points across first three elements across period 3
general increase as the metal ions have an increasing positive charge and increasing delocalised electrons and smaller ionic radius and so a stronger metallic bond
silicon in melting point across period 3
giant covalent structure- many strong covalent bonds and so a large amount of energy needed to overcome these bonds
phosphorus and sulphur in melting point across period 3
p4 has a lower melting point due to simple molecular structure. melting point determined by van der waals forces which are weak intermolecular force
sulfur is slightly larger molecular structure and so has higher van der waals and so slightly higher mpt
chlorine and argon melting point across period 3
chlorine lower melting point as it has smaller van der waals due to even smaller simple molecular structure
argon even smaller as it only exists as individual atoms and so small van der waals and so lower mpt
what is ionisation energy
ionisation energy is the minimum amount of energy required to remove one mole of electrons from one mole of atoms in the gaseous state
is ionisation endothermic or exothermic
always endothermic as they require energy
what effects ionisation
shielding- more electron shells between positive nucleus and negative electron that is being removed, the less energy is required as there is a weaker attraction
nuclear charge- the more protons there is the bigger the positive attraction and so more energy required to remove electron
atomic size- the bigger the atom the further the distance from the nucleus and so attractive force between nucleus and outer electron reduces and so easier to remove electrons
what is successive ionisation
the removal if more than one electron from the same atom
ionisation energy … as we go down a group
decreases because atomic radius increases, shielding increases
ionisation energy … as we go across a period
increases because proton number increases and shielding mildly decreases
why is there a decrease in aluminumin in ionisation energy
aluminium is in 3p sub shell - bohrs model didn’t explain subshells
why is there a decrease in sulfur in ionisation energy
as there is energy repulsion when there is two electrons in a subshell
