Topic 1.2.2 - Periodicity Flashcards
What is atomic radii?
The distance from the centre of the nucleus to the boundary of the electron cloud.
What is van der waals radius?
The radius where two atoms are touching and dividing the difference between the 2 nuclei by 2.
What happens to atomic radii across a period?
Decreases
because nuclear charge increases meaning more attractive force between nucleus and outer electrons.
What has higher ionisation energy helium or hydrogen?
Helium because it has greater nuclear charge therefore more energy required to remove electron.
This offsets the increase in electron in electron repulsion which alone would decrease heliums ionisation energy
What happens to ionisation energy across period 2 and 3.
It increases as nuclear charge increases.
Why does silicon have a high melting point?
Has a giant covalent structure.
Many strong covalent bonds require large amounts of energy to break.
Why does phosphorous have a low melting temperature?
It has a simple molecular structure.
Has weaker London forces.
Why does sulfur have a slightly higher melting point than phosphorous?
Has a larger simple molecular structure.
Has larger melting London forces that require more energy to break.
