periodicity Flashcards
What happens to the size of atoms down the periodic table
It increases
What is effective nuclear charge
Orbital energies depend on effective nuclear charge, it captures the electron’s energy dependant on quantum number l as well as n
What does effective nuclear charge depend on
Shielding penetration, Ztrue - S ( shielding constant)
Valence electron feels lower than Zeff than true nuclear charge- less stable.
What do orbital energies depend on
For non-hydrogen atoms electrons depend on n and l due to shielding and penetration. Orbital energies show largest difference in valence region.
They become more similar further away from valence region. Orbitals can cross in energy. Order only holds for neutral atoms.
What are slaters rules : Zeff = Z-S
1) electrons with a higher n contribute 0
2) electrons with the same number of n contribute 0.35
3) electrons with n-1 contribute 0.85
4) electrons with n-2.n-1, contribute 1
These rules only work for s and p electrons
What happens to effective nuclear charge across a row
There are more protons in the nucleus across the row, which overpowers the electrons that increase across the row. Therefore effective nuclear charge increases across the row.
What happens to effective nuclear charge down the group
It increases the effective nuclear charge and then remains effectively the same
How does ionisation energy depend on effective nuclear charge
effective nuclear charge increases across the row so the energy decreases.
How does ionisation energy change down the group
Zeff rises then is constant. n increases down the group. energy becomes less negative, so the ionisation energy decreases down the group.
How does electronegativity change across the row
Zeff increases, so electronegativity increases.
How does electronegativity change down the group
Zeff is constant, electrons are further away from the nucleus so they are less strongly attracted to the nucleus and electronegativity decreases down the group.
How do the size of atoms change across the group
Radius of atoms decrease as Zeff is higher so the electrons are pulled closer to the nucleus.
What happens to the radius of atoms down the group
Radius increases as Zeff is constant so electrons sit in higher n orbitals so they are further from the nucleus. RADIUS GETS LARGER DOWN THE GROUP
Why does the metal to non metal staircase happen
Metallic bonding is favoured by large diffuse orbitals and a low number of electrons. Across the row Zeff increases as orbitals get smaller and less diffuse. Down the group the orbitals get larger and more diffuse so metallic bonding is favoured.
How do the homo-nuclear bond strengths change down the group
The bonds get weaker as atoms are larger, more diffuse orbitals and overlap is lower
