The atomic radius of aluminium is bigger than gallium due to the poor shielding effect of the 3d orbitals.
Why does the electron in 3d orbital have a poor shielding effect than say 1s or 2s or 2p?
on an interesting note, atomic radius of lanthanide series decreases with increasing proton number, also due to the poor shielding effect by 4f electrons.
again, why does 4f electron have a poorer shielding effect? lastly, what is the difference between shielding effect and screening effect?
l
Originally posted by bluepie:The atomic radius of aluminium is bigger than gallium due to the poor shielding effect of the 3d orbitals.
Why does the electron in 3d orbital have a poor shielding effect than say 1s or 2s or 2p?
on an interesting note, atomic radius of lanthanide series decreases with increasing proton number, also due to the poor shielding effect by 4f electrons.
again, why does 4f electron have a poorer shielding effect? lastly, what is the difference between shielding effect and screening effect?
l
Originally posted by UltimaOnline:4f orbitals have a poorer shielding/screening effect compared to 3d orbitals which have a poorer screening/shielding effect compared to 2p orbitals which have a poorer shielding/screening effect compared to1s orbitals, because of two reasons :
The further away the (principal quantum) electron shell the orbital belongs to, the larger and hence more diffused the orbital and therefore the poorer the shielding/screening effect.
The shape of the orbitals also determine their effectiveness of shielding/screening : the shape of the orbitals are such that f orbitals are poorer shielders/screeners compared to d orbitals which are poorer shielders/screeners compared to p orbitals which are poorer shielders/screeners compared to s orbitals, even when in the same (principal quantum) electron shell.
In the context of A level Chemistry (instead of say, physics or engineering or Marvel's Agents of S.h.i.e.l.d), there is no difference between shielding effect vs screening effect. Cambridge will accept both terms eagerly with open arms.
what does a diffuse orbital mean? does it mean that there is a greater region of space to find an electron? how does a diffuse orbital cause a poorer shielding effect?
Originally posted by bluepie:what does a diffuse orbital mean? does it mean that there is a greater region of space to find an electron? how does a diffuse orbital cause a poorer shielding effect?
Originally posted by UltimaOnline:Yes, you're right. Imagine it's a freezing icy winter night. Which would keep you warmer (ie. shield you from the cold), a thick (ie. non-diffused) wooly jacket or a thin (ie. diffused) silk shirt?
For A level purposes (are you a student or a tutor? are you Singaporean taking the Singapore H2 syllabus, or you're a foreigner taking international A levels?), just use any analogy to help yourself understand. Cambridge will *not* require the A level candidate to explain the technical details of how the degree of diffusiveness of the orbital affects the strength of its shielding effect.
i'm taking the h2 syallbus, though cambridge does not require this knowledge, i am curious in how it works cause i like learning beyond the syllabus
i was serching for anomalies for trends in atomic radius in the periodic table and came across two phenonmenon "d block contraction " and "lanthanide contraction". the explanation imo was unclear to how diffusiveness of orbital affects shielding effect.
basically is it because there is a larger region of space for electrons to move about and hence the electrons are unable to shield the valence electrons from the positive nuceus as effectively as compared to say a smaller region of space where electrons has a higher probability of shielding the positive nucleus from the valence electrons?
Originally posted by bluepie:i'm taking the h2 syallbus, though cambridge does not require this knowledge, i am curious in how it works cause i like learning beyond the syllabus
i was serching for anomalies for trends in atomic radius in the periodic table and came across two phenonmenon "d block contraction " and "lanthanide contraction". the explanation imo was unclear to how diffusiveness of orbital affects shielding effect.
basically is it because there is a larger region of space for electrons to move about and hence the electrons are unable to shield the valence electrons from the positive nuceus as effectively as compared to say a smaller region of space where electrons has a higher probability of shielding the positive nucleus from the valence electrons?
Originally posted by UltimaOnline:Yes, that's right. Sounds like you'll enjoy Inorganic Chem a lot (take note that if you decide to take up H3 Chem in J2, it'll be Organic Chem rather than Inorganic; have you found out if you love Organic Chem as much as Inorganic?).
The d block contraction in particular (rather than the lanthanide contraction) could be asked by Cambridge as a challenging question one of these years (I've actually already prepared a BedokFunland JC question on it some time back, will probably upload it sometime in the next few weeks or so).
Thanks ultimaonline for your guidance and help i enjoy organic chemistry more than inorganic chemistry though, i've actually study abit of uni organic chem reaction [aldol condensation etc.]
Originally posted by bluepie:Thanks ultimaonline for your guidance and help i enjoy organic chemistry more than inorganic chemistry though, i've actually study abit of uni organic chem reaction [aldol condensation etc.]
Originally posted by UltimaOnline:You already take H3 Org Chem? So you're taking your H2 A levels this year? School candidate or private candidate? So you're a student?
Yup, student taking h2 chem a level this year and offer h3 chem, with some knowledge of uni org chem[i think]
Originally posted by bluepie:Yup, student taking h2 chem a level this year and offer h3 chem, with some knowledge of uni org chem[i think]
Originally posted by UltimaOnline:Excellent. I noticed that your "bluepie" user account is new. You created a SgForum account just to discuss Chemistry here? (I'm proud of you!) Btw, how did you find out that you can discuss Chemistry here at SgForums?
i'm a frequent lurker of this forum so i'm aware that you'll answer all sorts of chemistry doubts from forum users. i finally decide to create an acc and ask here because i couldn't find any good explanation on the internet haha
Originally posted by bluepie:i'm a frequent lurker of this forum so i'm aware that you'll answer all sorts of chemistry doubts from forum users. i finally decide to create an acc and ask here because i couldn't find any good explanation on the internet haha
Hi i have another question relating to the atomic radius of transition metals.
for element 1-20, going across a group, screening effect remains constant and the only factor affecting atomic radius is due to the increasing nuclear charge and thus increasing attraction between valence electrons and positive nucleus.
However, such a trend is not observed for transition metals; their atomic radius stays relatively unchanged even with increasing proton no. This is because electrons are added into the inner 3d subshells and not 4s subshell, and hence the screening effect increases. (is it correct to say this?) The increasing screening effect offsets the the increase in nuclear charge and thus attraction between 4s electrons and nucleus is relatively same. Hence, atomic radius remains relatively unchanged.
Are my explanations correct or is there a better way of phrasing it?
Originally posted by bluepie:Hi i have another question relating to the atomic radius of transition metals.
for element 1-20, going across a group, screening effect remains constant and the only factor affecting atomic radius is due to the increasing nuclear charge and thus increasing attraction between valence electrons and positive nucleus.
However, such a trend is not observed for transition metals; their atomic radius stays relatively unchanged even with increasing proton no. This is because electrons are added into the inner 3d subshells and not 4s subshell, and hence the screening effect increases. (is it correct to say this?) The increasing screening effect offsets the the increase in nuclear charge and thus attraction between 4s electrons and nucleus is relatively same. Hence, atomic radius remains relatively unchanged.
Are my explanations correct or is there a better way of phrasing it?