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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Using Quantum Mechanics to understand the size of an atom [closed]

What is the quantum mechanical approach of explaining the fact that: "The size of the atom increases when a new shell is filled" ??? I mean how do you explain this phenomenon using ideas of ...
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511 views

Why is Aluminium oxide amphoteric?

I was reading my book, in which it mentioned that aluminium and gallium oxides are amphoteric and and indium and thalium oxide are basic in their properties. But no explanation was given. My main ...
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Why does Calcium have a higher ionization energy than Aluminium?

Given their places on the periodic table I'd assume Aluminium has a higher ionization energy, because it has fewer energy levels, and is on a "righter" row on the periodic table, but in reality it is ...
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Electron affinities of the chalcogens and halogens

Here are the electron affinities of the 16th and 17th groups. The general trend for electron affinity down the group is that it decreases because of the increase in atomic radius.The exception of $\...
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Regular decrease in the atomic radius of 3d series

While comparing atomic radius, two factors are important: A. Decrease in size due to increase in effective nuclear charge B. Increase in size due to increase in shielding effect I was surprised to ...
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81 views

Is there an opposite to shielding effect? [closed]

I recently read about shielding effect and lowering of effective nuclear charge due to penetration of other electrons. I wonder while doing calculations involving Slater's rules the electrons from ...
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55 views

Why is ionization energy of indium less than gallium?

In group 13 we observe an irregular trend in ionization energy: B > Tl > Ga > Al > In. Gallium has a filled 3d subshell, but indium has a filled 4d and 3d subshell. Thus it should have more poor ...
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138 views

Why is platinum denser than gold?

The atomic masses of gold and platinum are 196.96657 u and 195.084 u respectively, meaning that (on average) an individual gold atom is heavier than an individual platinum atom. At the same time, the ...
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why lawrencium is placed in f-block elements although its last electron enters in 6d-subshell?

The electronic configuration of lawrencium ($\ce{Lr}$) is $\mathrm{[Rn] 7s^2 5f^{14} 6d^1}$. As its last electron enters the $\mathrm{6d}$ sub shell, it should be a part of $\mathrm{d}$-block elements,...
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51 views

Trend in atomic volume across a period [closed]

"Atomic volume decreases along a period, reaches a minimum at the middle, and then increases for the rest of the period" Why does the atomic volume, along a period, initially decrease, ...
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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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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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What is the structure of CF3 radical? [duplicate]

In the class, I was told that $\ce{H3C^.}$ has a trigonal planar structure with the unpaired electron in $\mathrm{2p_z}$ orbital. But $\ce{H3C -}$ has a trigonal pyramidal structure. But why does ...
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Why does solubility of Carbonate salts of Alkali metals in water increase down the group?

Carbonate salts have a very large anion so hydration energy should dominate over lattice energy. Since hydration energy is inversely proportional to radius of ion, I would expect Lithium to release ...
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What is the lattice structure of manganese?

A transition element is defined as the one which has incompletely filled d orbital in its ground state or in any one of its oxidation state. Zinc , cadmium and mercury are not typical transition ...
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Why doesn't core charge increase down a group? [closed]

Atomic radius increases down a group because the electrons feel a lesser attraction to the positive nucleus (due to shielding from inner shells). Why then, doesn't core charge decrease seeing as core ...
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11k views

What is the reason for the different solubility of silver halides in ammonia?

According to my knowledge, I know that $\ce{AgCl}$ dissolves in dilute ammonia, $\ce{AgBr}$ dissolves in concentrated ammonia and $\ce{AgI}$ does not dissolve even with concentrated ammonia. What is ...
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48 views

Is the magnitude of ionisation enthalpy and ionisation energy is same?

In my textbook it is written that ionisation energy and ionisation enthalpy are two different quantities. ionisation energy is the amount of energy provided to extract an electron from the outermost ...
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Why is the strontium ion smaller than the potassium ion? [closed]

The ionic radius of the $\ce{Sr^2+}$ ion is $\mathrm{132\,pm}$, while the ionic radius of the $\ce{K^+}$ ion is $\mathrm{152\,pm}$. Why is this the case? I would have thought that since $\ce{K^+}$ has ...
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Why is fluorine a oxidising agent?

An oxidizing agent pulls the electron cloud of the substance being oxidized towards itself, for example: $$\ce{F2 + 2 X- -> 2F- + X2}\qquad (\ce{X} = \ce{Cl}, \ce{Br}, \ce{I})$$ We also know ...
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How to tell which species has the highest ionization energy?

I am preparing for my final exam, and I am very confused about ionization energy. An example question would be: Between the species $\ce{Ne, Na+, Mg^2+, Ar, K+, $\&$~Ca^2+}$, which one has the ...
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Why is phosphorus trifluoride the strongest Lewis acid among the phosphorus trihalides?

I had read that for the trihalides of boron, boron trifluoride is the weakest Lewis acid due to backbonding. The order I had seen was - $\ce{BI3 > BBr3 > BCl3 > BF3}\$ $$\ce{}$ $- order of ...
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Scale to be considered for comparing electronegativities of nitrogen and chlorine

The Pauling scale gives the $\chi$ values of $\ce{N}$ and $\ce{Cl}$ to be $3.04$ and $3.16,$ respectively, but the Allen scale gives the $\chi$ values of $\ce{N}$ and $\ce{Cl}$ to be $3.066$ and $2....
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Comparing Electron affinity and electron gain enthalpy at 0 K

In my book it is given that first electron gain enthalpy is greater than second for elements. Should we compare the magnitudes in such cases or the actual numbers with signs? Does the same comparision ...
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why is lithium oxide so different from water [closed]

Take water and replace hydrogens with the next element down in the periodic table, and you get a white solid, nothing like water. https://en.wikipedia.org/wiki/Lithium_oxide Lithium itself is very ...
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Why does the electron affinity increase become more exothermic down group 2 and group 5?

It is generally true that the electron affinity becomes less exothermic down a group, because of the increase in atomic radius. There is a well-known exception that the electron affinity of Cl is ...
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384 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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108 views

Why aren't Boron and Aluminium assigned to group 3 of periodic table? What determines the group? [closed]

I've been curious about this 3D representation of the periodic table "Mendeleev's Flower" and was trying to study it, wondering if it reveals any regularities that are not obvious from classic ...
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Confusion between electronegativity and electron affinity

Electronegativity is a chemical property that says how well an atom can attract electrons towards itself. The electron affinity of an atom or molecule is defined as the amount of energy released ...
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Why is the first energy of ionization of oxygen lesser than that of nitrogen? [duplicate]

The following question arises from a question I found in my book. Experimentally it has been determined that the value of the first energy of ionization of oxygen is lesser than the first energy ...
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368 views

Reorganization during ionisation for d block elements

This is a quote from my textbook: The irregular trend in the first ionisation enthalpy of 3d lmetals,can be accounted for by considering that the removal of one electron alters the relative ...
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Is strontium more metallic than sodium? If yes then why?

I got an MCQ in my examination, "Which one of the following is more metallic?" and the options were Sr, Na, Be or Aluminium. I know that sodium is more metallic than Be or Al but my mind stuck on ...
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Why Zn has highest ionisation enthalpy in 3d series?

Zn which has the highest ionisation enthalpy in 3d series.The reason given in my textbook is: The value of zinc is higher because it represent ionisation from 4s level. This is not correct because ...
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Shielding effects and atomic size [closed]

The atomic size on going from aluminum to gallium decreases because of poor shielding effect of the $(n-1)d$ electrons, but on going from copper to zinc, the size increases due to the same shielding ...
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Why does hydrogen have a lower ionization energy than fluorine?

I found here that the ionization energy of hydrogen is $\pu{1312kJ/mol}$ and for fluorine, it is $\pu{1681kJ/mol}$. Now clearly, from the data, we can see that hydrogen has a lower ionization energy ...
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Why do the trends in reactivity not apply for francium?

Why is francium not included in the reactivity series? Why is potassium considered more reactive than francium? I know that reactivity increases down the group, but why does it not apply here?
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For which pair of species is the difference in radii the greatest?

For which pair of species is the difference in radii the greatest? (A) $\ce{Li}$ and $\ce{F}$ (B) $\ce{Li+}$ and $\ce{F^-}$ (C) $\ce{Li+}$ and $\ce{O^2-}$ (D) $\ce{O^2-}$ and ...
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319 views

What do you mean by “periodic” in the periodic table? [closed]

Modern periodic law states: “The physical and chemical properties of the elements are periodic functions of their atomic numbers”. But I don't think this is so! (Forgive me for my stupidity. But ...
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Why is there a discrepancy among sources on the atomic radius of some elements?

My book says the atomic radius of gallium is less than that of aluminium, but I found out different atomic sizes on different sites. For example, this says gallium is 136 pm and aluminium is 118 pm, ...
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200 views

Electronegativity of heavier elements of Group 15

While reading about p-block I got to know that in Group 15 elements electronegativity value decrease down the group but amongst the heavier elements difference is not that much pronounced. I ...
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How ion size/electronegativity influences strength of an acid

My prof was explaining how we can use the structure of acids and bases to rationalize relative strengths (ie: acid X is stronger than acid Y because ...). He then went on to explain how when ...
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216 views

Is acidic character related to reducing power?

My book says that the acidic character of halogen acids increases on going down the group because the bond strength decreases, making it easier to release the $\ce{H+}$. But I also know that $\ce{HI}$...
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856 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 ionization ...
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Melting and boiling points of transition elements

The melting and boiling points of transition elements increases from scandium ($1530~\mathrm{^\circ C}$) to vanadium ($1917~\mathrm{^\circ C}$). They increase because as we go across the group, we ...
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Can you calculate the properties of a substance based solely on its atomic properties?

I'm trying to write some software that I can use to determine, roughly, what the physical properties of a pure substance are. I know I could just use a database of the known properties of each element,...
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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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824 views

Atomization enthalpies of transition elements

So, my book says that transition elements have higher enthalpies of atomization than other elements (say s- or p- block) because of stronger metallic bonding, primarily due to large number of unpaired ...
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1answer
260 views

Atomic radii and why does it decrease in a period [closed]

Why do atomic radii decreases as you move from left to right across a period
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282 views

Effective nuclear charge and Ionization energy

A common reason given on why 3rd ionization energy > 2nd > 1st is because of increasing effective nuclear charge. As per my book $Z_\mathrm{eff}$ = Atomic number $-$ Number of inner electrons. Now ...
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How would one determine an element simply by looking at its binding energy?

I am self studying MIT OCW chemistry 5.111 2014, one of the lecture questions states the following: Consider a neutral atom with 8 distinct electron binding energies: −14 eV, −28 eV, −94 eV, −218 ...

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