Periodicity Flashcards
chap 8
What is the trend of atomic radius across a period? Why? (4)
- Dec
- bc of inc in nuclear charge density (no. of protons)
- and same amount of shielding
- so nucleus pulls e- in closer
What is the trend of 1st ionisation energy across a period? Why? (4)
- Inc
- due to inc in protons
- and atoms getting smaller
- so stronger nuclear attraction
What is the reason for the dip in 1st ionisation energy between Mg and Al? (2)
- change in orbital!
- as Mg is in s block and Al is in p block, p is in higher energy than s
What is the reason for the dip in 1st ionisation energy between Si and P? (2)
- P has 3p3 as its highest orbital and Si has 3p4 as highest orbital
- as Si has an electron pair in its p orbital, due to repulsion theory, it is easier to remove
What is the trend in electronegativity across a period? Why? (3)
- inc
- due to inc in nuclear charge, so nucleus can pull e- more strongly
- due to dec in atomic radius, so less shielding
Why is there a big jump between the melting and boiling points of Si and P?
Si has a giant covalent structure whereas P is simple covalent, so Si requires more energy to break strong covalent bonds
Are pos or neg ions smaller than neutral atoms? Why? What sometimes happens to pos ions that makes them extra small?
- Pos ions are smaller
- less e- = less repulsion
- sometimes pos ions lose a shell, so there’s less shielding and electrons attracted more tightly to nucleus
Does atomic radius inc or dec down group 2?
INC
more electron shells= bigger atoms
Does 1st ionisation energy inc or dec down group 2? Why?
DEC
more shells/shielding means less nuclear attraction (so less energy needed to overcome it)
Do melting points inc or dec down group 2? Why (2)?
DEC
- weaker metallic bonding
- as metal ions are bigger
