Questions tagged [periodic-trends]

Trends which are observed in the properties of elements as you move along the periodic table in a given direction.

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94 views

Relative orbital energies of Mn and Ni

In this MO diagram, why are the atomic Mn $3d$ orbitals higher in energy than the Ni $3d$ orbitals?
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66 views

Trends in Slater's constant

I am aware of the various Slater rules to calculate the effective nuclear charge, $Z_\mathrm{eff}$ However, how can I decide the order in which the orbitals 2s, 3s, 3d, 3p, 4d, and 4f stand when ...
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157 views

How to rationalise the trend in the covalent radii of the transition metals?

Why do the covalent radii of transition series decrease at the start rapidly, then become almost constant and at the end of series begin to increase from left to right in periodic table?
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2k views

Bond Energy in P-O , S-O , Cl-O

My text says that Bond energy between P-O , S-O , Cl-O follows the trend P-O < S-O < Cl-O. But I think it should be a reverse of what's given because more the electronegativity difference ...
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285 views

Why hydrogen disulfide and not hydrogen persulfide?

Recently, I was checking on this question and I was thinking of the name of the compound $\ce{FeS2}$. Later I checked the name in the answer to be iron disulfide. I found the following statement in ...
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1k views

How to compare the oxidizing power of perhalate ions

In my book the oxidizing power in descending order of the following is given as: $\ce{BrO4-} > \ce{IO4-} > \ce{ClO4-}$ My doubt is regarding their order of oxidizing tendency. I thought that ...
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76 views

Why are the Covalent Radii of Ruthenium and Osmium So Similar?

Osmium and Ruthenium have covalent radii 144 and 146 respectively (according to Wikipedia). How are these values so similar when Osmium has 32 more electrons, with another filled p, s, and f orbital ...
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145 views

H-N-H bond angle in ammonia boron trifluoride adduct

In the reaction: $\ce{NH3 + BF3 -> NH3-BF3}$ does the HNH bond angle increase or decrease? Surely, the FBF bond angle decreases because boron changes from $\ce{sp^2 -> sp^3}$. But how can we ...
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84 views

What proof is there that the “Island of Stability” exists?

Often I see people talking about an "Island of Stability" existing for super-heavy elements on the periodic table, but I don't see any reason to thinks this exists? Surely the heavier you go the more ...
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2k views

Comparing electronegativities of aluminium and gallium

If I were to compare the electronegativities of Al and Ga, shouldn't I be saying that the electronegativity of elements (in general) decreases down the group, I say this by thinking of the position of ...
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50 views

Will O or S accept an electron more easily?

O has more electronegativity than S but S has more Electron Gain enthalpy than O. How do we decide, which one pulls the electron more easily? In other words, Electron gain enthalpy dominates or ...
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272 views

Why do some elements such as polonium not follow the trend of decreasing atomic radius?

Most of the periodic table follows the trend of increasing radius as you move down a family and decreasing radius as you move across a period. Why is this trend not observed for polonium?
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467 views

Density of d-block elements

Something that confuses me slightly is the trends in density when comparing periods 4, 5, and 6 in the d-block. Looking at periods 5 and 6, the density peaks at group 8, with ruthenium and osmium, ...
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133 views

Comparision of the Ionisation Energy Change of the alkali metals and noble gases?

Currently I compare the ionisation energys of the alkali metals: Li: $\pu{0.52 eV}$ Na: $\pu{0.50 eV}$ K: $\pu{0.42 eV}$ Where only a slight drop (appr. remain constant) occurs. This ionisation ...
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92 views

Boiling Point trend

Why does group 13 and 14 show reverse the trend of boiling point? In other groups, boiling point increases down the group but here it decreases.
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474 views

Trends in the covalency of bonding across the transition metals

I am under the impression that the covalent character in the bonding of transition metal compounds increases across a group; in fact I think this is why they're called transition metals (a transition ...
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1k views

Why is ionisation energy of bismuth lower than lead?

Why is ionisation enthalpy of Bismuth less than that of Lead for it just comes after the latter in periodic table? First ionisation energy of bismuth is 703 kg/mol while that of lead is 715 kg/mol. I ...
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2k views

Why there is an exception in melting and boiling point in p block?

Why is the boiling point and melting point of 15th group and 16th group has an exception? We know that as molecular mass increases boiling point and melting point also increase. So, down the group 15 ...
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2k views

How to explain the periodic trends in boiling points in groups?

Observing the trend of boiling points of the compounds listed, choose the appropriate terms to fit into the blanks: \begin{array}{lr} \text{Compound}& \text{boiling point}\\\hline \ce{H2Te} &...
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26 views

Why is the Ionization Energy of Germanium less than that of Silicon?

I've read that in the 13th period, Ga has higher I.E. than Al because of the filling of the d-orbitals in Ga. The text said they have low penetration,hence they don't shield well and the effective ...
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36 views

Exception in trend of increasing ionisation energy across a period

One exception to the trend of increasing ionisation energy across a period in e.g. period 2 is going from N to O. There is no loss of exchange energy in I1 of O, but there is 2K lost in I1 of N, hence ...
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433 views

Second ionization energies of copper(Cu) and silver(Ag)

The ionization energies of copper and silver are First ionization energy: Cu-745.5 kJ/mol Ag-731.0 kJ/mol Second ionization energy: Cu-1958 kJ/mol Ag-2073 kJ/mol Now, looking at the ...
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166 views

Mismatch in the trends of atomic size and atomic radius

In the periodic table, the atomic radius decreases as we move from left to right in a period. However, the atomic volume should also decrease as a result of the decrease in atomic radius, as volume is ...
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451 views

Rationalising the trend of standard electrode potentials between the +II and +III oxidation state of first-row transition metals

Trends in standard electrode potentials of d block elements: An examination ofthe $E^0 (\ce{M^3+}/\ce{M^2+})$ values (Table 8.2) shows the varying trends. The low value for Sc reflects the ...
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121 views

Periodic trends on half cell potentials

In a practice examination that I'm using to study for my upcoming midterm, one of the questions asks to choose three elements from a row of the periodic table and to give the order of the increasing ...
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914 views

Trend of second Electron Affinity for N,O,F,P,S,Cl

I am aware of the definition of electron affinity and electron gain enthalpy (EGE). N has positive EGE1, and EA of P,S,Cl is more than N,O,F respectively. I want to arrange them in order of their EA2 ...
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2k views

Relation of Boiling Point and Melting Point with the reactivity of an element

When we look at the trends of periodic table, there is an interesting correlation to be noticed. Along a period, when we look at the trends in reactivity of an element( Both due to electropositivity ...
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541 views

Why Don't Sulfur Atoms Hybridize?

I am doing some chemistry problems with given answers, and supposedly the $107^{\circ}$ and $92^{\circ}$ bond angles in $\ce{H_2O}$ and $\ce{H_2S}$, respectively, is due to the fact that"$\ce{O}$ uses ...
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99 views

Why is Iron (Fe) difficult to reduce?

$\ce{Fe^3+ + e- -> Fe^2+} \quad +0.77$ $\ce{Fe^3+ + 3e- -> Fe} \quad -0.04$ $\ce{Fe^2+ + 2e- -> Fe} \quad -0.41$ $\ce{Zn^2+ + 2e- -> Zn} \quad -0.76$ $\ce{Co^2+ + 2e- -> Co} \quad -0.29$...
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841 views

Difference in the change in oxidation states of transition elements and p-block elements

In transition elements the oxidation states differ by one (+2 to +7 in Mn). However, in the p-block elements, the oxidation states differ by two (-1,+1,+3,+5 in the halogen group). Why is this so?
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419 views

How does the electron configuration of platinum relate to its stability?

Does platinum's electron configuration, [Xe] 4f14 5d9 6s1, influence its reactivity and stability? Is the electron configuration the primary contributing factor to platinum's relative inertness? ...
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4k views

Ionization energy and Electron Affnity

Which of the following statements correctly interprets the relationship between ionization energy, atomic radius Electron affinity when comparing two atoms. The correct choice as per my instructor ...
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15 views

n+l rule for first member of lanthanide and actinide series

as we all know that if the value of $n+l$ is same then the orbital with lower value of $n$ will get filled first so in case of first member of lanthanide series the configuration is $(\ce{Xe})\mathrm{...
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183 views

Ionization enthalpy for group 13 elements

The ionization enthalpy for elements along a group generally reduces. But there is an exception for group 13 elements and the order is not uniform. The order is: B>Tl>Ga>Al>In According to ...
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37 views

Why don't ionization energies vary linearly going down Group 2?

I understand why the 1st ionization energies (1st IEs) of Group 2 elements decrease down the group. However, why is the difference between 1st IEs of successive elements greater for Be to Ca and ...
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83 views

Ionisation energies of Carbon and Boron

The first ionisation energy of Carbon atom is greater than that of Boron atom whereas, the reverse is true for the second ionisation energy. In order to explain the above statement I considered the ...
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164 views

Why is fluorine a oxidising agent?

Fluorine has very high charge/mass ratio as it is very small in size, its electron gain enthalpy is very high. Oxidizing agent pulls the electron cloud of the substance being oxidized towards itself, ...
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2k views

Abnormal ionisation energy trend: Group 13 and 14

I was going through some ionisation energy data, where I came across the following: Ionisation energy order for Group 13 and 14: B > Al ≈ Ga > In < Tl C > Si > Ge > Sn < Pb What could be the ...
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632 views

Random order of melting points of group 2 elements

Compare the melting points of $\ce{BeF2, MgF2, CaF2, SrF2, BaF2}$. Actual order is $\ce{ BeF2 > CaF2 > SrF2 > BaF2 > MgF2}$. I have worked out the following things while comparing ...
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3k views

How does increasing the molecular mass of compounds of homologous series affect solubility?

First of all, I know that increasing the molecular mass decreases the solubility of that compound wrt, of another compound of the homologous series in organic chemistry. My question is how? My text ...
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How does the stability of Group I and Group II carbonates change as you descend the groups?

I thought that as you descend both the groups, the carbonates get more stable. Is this because of the ions decreasing in charge density down the groups (so less distortion for the carbonate ion) so ...