Inorganic- Periodicity Flashcards
What is the definition of 1st ionisation energy?
The minimum amount of energy needed for one mole of the outermost electrons to be removed from one mole of atoms in a gaseous state
What are the elements in period 3?
Na, Mg, Al, Si, P, S, Cl, Ar
What is periodicity?
Pattern in properties across a row which is repeated in each row
What is the atomic radius trend across Period 3?
The atomic radius decreases across a period
Why does the atomic radius decrease across a period?
- more protons in nucleus
- same amount of shielding
- stronger attraction between nucleus and outer shell electrons
What is the trend in 1st ionisation energy across Period 3?
The 1st ionisation energy generally increases across a period
Why is there a general increase in the 1st ionisation energy across a period?
The increasing protons means there is an increasing attraction between outer shell electrons and the nucleus
(more protons therefore stronger attraction)
What are the exceptions for the general increase in 1st ionisation energies across period 3? (group 2-3 dip)
For aluminum, the outer electron has just entered a new subshell (3p) and therefore is slightly further from the nucleus meaning it is easier to remove, this creates a dip between Mg and Al because the 3p orbital has a slightly higher energy than the 3s
What are the exceptions for the general increase in 1st ionisation energy across period 3? (group 5-6 dip)
For sulfur, the fourth electron in 3p has been paired with another and so repulsion happens, making the electron easier to remove, this creates a dip between P and S which is due to electron pair repulsion
What is the trend for melting and boiling points across period 3?
The melting and boiling points vary across period 3- it depends on the structure and the bonding of the elements
What is the mp/bp like for silicon?
Silicon has the highest melting point in period 3, because it is a giant covalent structure. Each Si has 4 strong covalent bonds so a great number of bonds need to be broken to break up Si
What is the mp/bp like for sodium, magnesium and aluminium in period 3?
The temperatures increase as you go along these three elements because the charges on the ions increase so more electrons join the delocalised sea of elections that hold the giant metallic lattice together.
Therefore, stronger electrostatic forces of attraction
What is the mp/bp like for the non-metals in period 3?
The temperatures of non-metals depend on Van der Waals forces between molecules- this depends on the number of elections and how close the molecules pack together.
Larger molecules have stronger Van der Waals forces
What element has the lowest mp/bp in period 3 and why?
Argon - because it has a full outer shell of elections and very weak Van der Waals forces
