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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Ionization energy of neon vs its cationic counterpart

Which requires more ionization energy: $\ce{Ne}$ or $\ce{Ne+}?$ It seems to me like it should be neon because of noble gas configuration, but the answer given is $\ce{Ne+}.$ Does this anything to do ...
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25 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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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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33 views

Predicting atomic weight and density of calcium [closed]

I have a question from school: Assuming that the element Ca had not been discovered, predict using the properties of the known element surrounding Ca its own properties such as its atomic weight ...
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28 views

Comparing the EA [duplicate]

What is the electron affinity trend for the oxygen family? I am interested in the question above. I am aware that EA of O $>$ EA of S, but what about the others? Which is having more EA: O or Se? ...
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147 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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1answer
52 views

why lithium is less reactive than sodium? [duplicate]

Lithium lies above sodium in a group and is also smaller in size. According to periodic trend reactivity decreases from left to right in period and down the group.
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43 views

Relationship between electronegativity and atomic radius [closed]

Would someone please explain in detail the relationship between the two? I understand that atomic radius is related to ionisation energy but I can't see how atomic radius may be related to ...
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1answer
151 views

Which is more metallic: boron or silicon?

I read somewhere that boron is more metallic. Is it correct? If so, can you please elaborate? The reason why I'm confused is because 2 factors come into play here: When you move towards right, ...
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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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287 views

Change in electronegativity order down a group from groups 13-16 to group 17

In general, going down a group Zeff initially increases but then becomes approximately constant, while electrons are in higher n orbitals, hence valence electrons on average further from nucleus, ...
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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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73 views

Why do metals form cations?

metals that have a low number of occupied shells such as lithium and potassium should have a stronger electrostatic attraction to their nuclei, so what causes them to always lose their electrons ...
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68 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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1answer
496 views

Thermal stability order of NaF, MgF2 and AlF3

I came up with a question to arrange thermal stability order of $\ce{NaF}$, $\ce{MgF2}$ and $\ce{AlF3}$ and I think the answer is $\ce{NaF>MgF2>AlF3}$ because $\ce{Na+}$ has largest ionic radius ...
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160 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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1answer
40 views

Lanthanoid Contraction

Why is the radius of Europium so unusually high and out of the general trend ? Moreover, at different sources I am getting different values of radii. In some (e.g., Wikipedia) the radii are following ...
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112 views

How can an electron shield another electron of the same subshell?

While I was preparing for my upcoming exams, I stumbled upon this sentence which is bothering me quite a bit: The contraction of the lanthanoids is due to the imperfect shielding of one electron by ...
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1answer
118 views

Relationship between effective nuclear load and periodic properties

The effective nuclear charge is defined as the net positive charge experienced by an electron in a polyelectronic atom. It can be calculated using the well-known Stars Rule. Once I have calculated ...
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75 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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2answers
451 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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3answers
2k views

If Mg(OH)2 is insoluble, why does the reaction of MgO and water produce a slightly alkali solution? [closed]

The equation of the reaction is: Mg(OH)2 + H2O -> Mg(OH)2. Why is it that this reaction produces a solution of around pH 9? There are no OH- ions produced.
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142 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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469 views

Why it the electron affinity of beryllium is greater than nitrogen? [closed]

As we know that fully filled electronic configuration is more stable than half filled electronic configuration, so in my opinion beryllium's electron affinity should be less than nitrogen's. Is my ...
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1answer
426 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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Comaparing melting points of group 14 elements [duplicate]

I found that melting point of $\ce{Sn(232°C)}$ is less than $\ce {Pb (327.5°C)} $ but i also saw that the bond enthalpy of $\ce {Sn-Sn(187.1 ±0.3 kJ mol^{-1})}$ is more than $\ce{Pb-Pb 86.6 ±0.8 kJ ...
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1answer
218 views

Octet rule violation in Period 2 elements [duplicate]

My textbook states, Period 2 elements typically obey the octet rule. Period 3 and later elements can expand their valence shells. Elements in Periods 5 and 6 of the p-block show variable valence (...
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1answer
397 views

Why is the melting point of hydrogen fluoride lower than that of ammonia?

The melting point of hydrogen fluoride is -83.6°C, as compared to that of ammonia, which is -77.73°C. How does this make any sense? Both hydrogen fluoride and ammonia show hydrogen bonding, which "...
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1answer
701 views

Is there any difference between negative electron gain enthalpy and electron affinity?

Electron affinity is the amount of energy "released" during the addition of an electron in the valence shell of an isolated gaseous atom. The sign convention is opposite to that of thermodynamics ...
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732 views

Why is the electronegativity of indium greater than that of thallium?

Why is the electronegativity of indium greater than that of thallium? One possibility which I had assumed was the poor shielding effect by the d and f orbitals which leads to an increase in 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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288 views

What is the true depiction of the periodic table?

Normally with the periodic table the lanthanide series is separated out because it's long and would make the table wide. I looked for an expanded version and found this: I found it kind of strange ...
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1answer
3k views

Rule to determine the total number of elements in a period [closed]

If each orbital can take maximum of 3 electrons, then total number of elements in 2nd and 4th periods respectively are = ? I am not aware of the rule which helps to determine the total number of ...
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1answer
4k views

Why does oxygen have less negative electron gain enthalpy than sulphur? [duplicate]

Oxygen has less negative electron gain enthalpy than sulphur. This statement is given in my book with a short reason: due to compact size of oxygen I'm unable to understand why. I would ...
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1answer
1k views

Why does hydride acidity increase across period and down group in periodic table?

Why exactly does hydride acidity increase across period and down group in periodic table? What is the explanation with respect to electrons? I can't figure this out because for 1st period etc H is an ...
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1answer
651 views

Why does the stability of hydrides decrease down the group in nitrogen family?

Why does the stability of hydrides decrease down the group in nitrogen family? Does this have to do with the fact that $\ce{NH3}$'s $\ce{N}$ is hybridised ($\ce{sp^3}$) while the rest of the group ...
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2k views

Comparing ionic character of group 1 elements

According to Fajan's rule ionic character should increase down the group as the size of cation increase. So it must be $$\ce{LiH < NaH < KH < RbH < CsH}$$ However, the following two ...
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1answer
2k views

Difference between basicity and reducing character

My understanding of basicity and reducing character: Reducing character is the ability of a substance to reduce something else. So it itself must get oxidized. Since $\ce{BiH3}$ has a large radius, ...
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1answer
1k views

Trends in ionization energy in the second period [closed]

Question Which element among the following has the highest ionisation energy: fluorine, oxygen, neon. I know that all these elements belong to period 2 and ionisation energy increases from left ...
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3k views

Boiling point trend in group 13

My Theory: Since atomic mass increases down the group, the van der Waal's forces should also operate to a greater extent, thereby making it difficult to change the phase of the substance. Hence, ...
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1answer
372 views

Why does cobalt have no negative charge?

I would like to know why cobalt cannot have a negative charge (or at least why a negative charge for cobalt isn't typical). I am not sure where I have gone wrong in my reasoning. The electronic ...
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965 views

Why does hydration of ions depend on their charge to area ratio?

The following is written in my book Concise Inorganic Chemistry by J. D. Lee. Hydration energy, hydrated radius and hydration number of a particular ion depends upon charge per unit area. Hence ...
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685 views

Trend in reducing property of dioxides

I am not sure of the explanation for the following statement: The reducing property of dioxides of group 16 elements decreases from $\ce{SO2}$ to $\ce{TeO2}$. Is the statement valid? If yes, how ...
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1k 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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1answer
2k views

Order of second ionization energy for cations

Why is the correct order of second ionisation potential of $\ce{Li , Be , B , C }$ such as: $\ce{Be} <\ce C <\ce B <\ce{Li} $? I understand that $\ce{Li+}$ has a stable inert gas electronic ...
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491 views

Why doesn't D block contraction affect the other P block groups 14 15 16 etc

Usually we come across anomalies in the trends of periodic properties for example the size [Atomic radius value from Raymond Chang Chemistry 9th Edition] of Gallium (135 pm) is smaller than Aluminium (...
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132 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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1answer
968 views

Electronegativity trends: Is it more important to prioritize families or periods? [closed]

I know that an atom that an atom is more electronegative as it moves up a group or right on a period (in terms of the periodic table). So if you have two atom that is diagonally across from each ...
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448 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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1answer
68 views

Quickly deduce block (s, p, d …) from atomic number [closed]

A question from previous year papers of IIT JEE. There's not enough time to write the electronic configuration in the exam. Please suggest a quick, objective approach.