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

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Why is BCl3 a monomer whereas AlCl3 exists as a dimer?

What makes dimerization possible in $\ce{AlCl3}$? Are there 3c-2e bonds in $\ce{AlCl3}$ as in $\ce{BH3}$?
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40 views

Why does density decrease across the period 4 and 5 transition metals?

I know that density decreases across period 4 because the last two elements are liquids and gases which means that their densities are less but why are the densities increasing and then decreasing ...
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35 views

Periodic Trends of Zeff and Electronegativity

The effective nuclear charge $Z_\mathrm{eff}$ increases from left to right and from top to bottom. Can you explain why it increases from top to bottom? Also can we explain the periodic trend of ...
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75 views

Why are the atomic radii of iron, cobalt, nickel, and copper almost the same?

So we have to select the set of elements which will have almost the same atomic radii: O, S, Se, Te Li, Be, B, C Fe, Co, Ni, Cu Now I googled the atomic radii of the third set and found them to be ...
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Which element has a greater second electron affinity, sulfur or oxygen?

I found a question asking the above which states that sulfur has a lesser second electron affinity than oxygen. But since the inter-electronic repulsion in sulfur is lesser, shouldn't it be willing to ...
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76 views

Color of halogens

Why does the color of the halogens deepens as we go down the group? also why there is a change in physical state of halogens down the group? \begin{array}{c|c} \mathbf{Gas} & \mathbf{Color} ...
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54 views

Bond angles for the hydrides

I noticed the fact that all the hydrides of the elements belonging to group IV has bond angle 109.5° while in group V it varies from 107.3° for $\ce{NH3}$ to 91.3° for $\ce{SbH3}$. Similarly we see in ...
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81 views

Trend in the melting point down the group

We know the the atomic radii increase down the group. So less energy is required to pull the outermost electron as we go down the group and gradually melting points decreases down the group. The ...
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74 views

Does caesium or francium have a lower ionization energy?

$\ce{Cs}$ and $\ce{Fr}$ are in the same group of lowest first ionization energy, but which element has the lowest ionization energy, and why?
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Why are there peaks in electronegativities in d-block elements?

Looking at the Pauling electronegativities in the Periodic Table (below, from ChemWiki): Asides from the overall trend of increasing electronegativity across and up the Periodic Table (towards ...
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Relation Between Degree of Hydration and Electropositivity

Why are salts of strongly electropositive elements less heavily hydrated in aqueous solution than the those of less electropositive elements? Shouldn't it be the other way round as the salts of ...
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283 views

Diagonal relationships in the Periodic Table

I have often wondered about diagonal relationships between elements on the periodic table, and the most often cited explanations revolve around charge-density considerations. But other than that, ...
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Electron affinities of the chalcogens and halogens

Here are the electron affinities of the 17th and 18th 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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92 views

Anomalous trends in ionization energy

I want to address two exceptions in the trend of ionization energy across the period, that are causing me problems: Taking the second period as an example : The two exceptions from the general trend ...
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482 views

Is there a function to approximate atomic mass from the atomic number?

The product of $2Z$ generally approximates the value of $m_\mathrm{a}$ of atoms that comprise relatively few protons. Whereas, the product of $2.5Z$ generally approximates the value of $m_\mathrm{a}$ ...
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119 views

Variation in atomic radii of elements in different blocks?

If we look at the values for the atomic radii (look at the table here), we can see that they rapidly decrease across the period initially. Looking at the first period, The graph is pretty steep ...
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Available orbitals for promotion

I am under the impression that elements from the third period onwards can promote electrons into d orbitals to form hybridised orbitals. Why would an element in the third period promote an electron to ...
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228 views

Dipole Moment Anomaly in Fluorine and Chlorine Compounds. What factors affect them?

I was checking dipole moment orders, and came across a very peculiar result: Methyl fluoride has lesser dipole moment than methyl chloride, but hydrofluoric acid has more dipole moment than ...
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78 views

What type of bonding occurs in isolated silicon?

Would isolated silicon engage in network covalent bonding as quartz does or would it engage in a different kind of bonding? Would germanium display similar qualities? I am asking what is the bonding ...
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159 views

Why does ionization energy increase as we go from left to right in a period?

Why does ionization energy increase as we go from left to right in a period? In my textbook, the explanation is as follows: "This is consistent with the idea that electrons added in the same ...
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105 views

Why are inert gas (especially Xenon) compounds powerful oxidizing agents?

I am curious as to why compounds with inert gases, such as $\ce{XeF4}$, $\ce{XeF2}$, and $\ce{XeO3}$ are considered powerful oxidizing agents. I would attribute the phenomenon to the highly oxidized ...
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139 views

Why is arsenic more chemically similar to phosphorus than is nitrogen?

Why is arsenic more chemically similar to phosphorus than is nitrogen (to phosphorus)? I thought that it may be because both phosphorus and arsenic have d orbitals (albeit one has one that is filled ...
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64 views

Why is the melting point of TiCl4 lower than TiCl3

I was wondering why the melting point of $\ce{TiCl4}$ was below that of $\ce{TiCl3}$ The melting point of the former is $\ce{-25 Celsius}$ whereas the latter is $\ce{425 Celsius}$ . Thanks!
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Second ionization potential of Gadolinium

I notice that Gd has a second ionization potential which is significantly higher than would be expected from the general trend in the lanthanides (see this paper p. 945 for a graph). What is the ...
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283 views

Why does the second electron affinity has an opposite sign of the first one?

Most of the first electron affinities are positive, therefore the second ones are negative, and vice versa. but why? SPECIALLY WHEN THE FIRST ELECTRON AFFINITY IS NEGATIVE .. WHY THE SECOND ONE IS ...
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How adding one more electron increases the ionization energy?

Elements of group 6A, compared to 5A, require less ionization energy due to the paired electrons of 6A. But a question arises: why does group 7A, compared to group 6A, require more ionization energy ...
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214 views

Effect of effective nuclear charge increase on the stabilization of 2s and 2p orbitals

Are 2s or 2p orbitals more stabilized when going from left to right in the period? There are good arguments for both possible answers: 1) 2p orbitals are more stabilized because they penetrate less ...
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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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192 views

Basicity of Group 15 hydrides [duplicate]

Why does the basicity of Group 16 hydrides ($\ce{NH_3,~ PH_3,~ etc}$) decrease down the group ? I know that its Lewis Base nature due to the lone pair but wouldnt the more EN element be less ...
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842 views

Memorizing the periodic table

Several people have said that the key to understanding chemistry is through memorizing the periodic table. I want to ask if there is a simple technique to learn it, or if I just have to remember ...
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47 views

Why is ionization potential considered a periodic property?

Why is ionization potential considered a periodic property??? A periodic property is a one which appears at regular property But we see that every element has some kind of ionization potential
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How does absence of nd orbital in Oxygen affect its valency?

The original question was 'Oxygen exhibits Oxidation state -2 to +2 but other elements of grp 16 exhibit only +2,+4,+6. Explain Why'. In the solution given i can't understand meaning of this line 'It ...
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612 views

Why do screening effect decreases due to d-orbital?

I am currently learning about p-block elements. In that in 13th group from Boron to Aluminium atomic radii increases. From Aluminium to Gallium atomic radii decreases. From Gallium to Indium atomic ...
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What is the reason behind choosing the specific elements used for the synthesis of heavier elements?

Attempts to synthesize still undiscovered elements This is derived from the wiki page: "extended periodic table" and is one of the many examples d or f block elements are used in ...
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Periodic trends: why is effect of protons greater than electrons?

Why is it that adding protons has a greater effect than electron-electron repulsion on periodic trends like atomic radius and ionization energy (assuming # of shells constant)? It seems that if ...
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390 views

Why is Osmium the densest known element

Why is Osmium so dense, Even if we have more heavy elements post to it.
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Factors of London Forces

In class we learnt that the London forces become stronger as the relative molecular mass increases. Not just as in organic chemistry but in things like the halogens. However, as I understand, the ...
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858 views

Periodic trend in difference of energy between the s and p orbitals

Why does the difference of energy between the 2s and 2p orbitals of the second period elements increase with increasing atomic number? Does this difference increases by moving down a group, e.g. is ...
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554 views

Outermost electronic configuration of f block elements

I have a doubt regarding the general outermost electronic configuration of f block elements. Why is it $(n-2)f^{1-14}(n-1)d^{0-1}ns^2$. The only exception i thought to this formula was thorium ...
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82 views

Can you calculate the properties of a substance based soley 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 ...
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677 views

What's the order of oxidising strength of the oxyacids of Chlorine?

What I have been told is that the acidity of the four oxyacids of Chlorine increase in the order $\ce{HOCl} < \ce{HOCl2} < \ce{HOCl3} < \ce{HOCl4}$. I have also been told that the oxidising ...
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510 views

Determining the group number of an element from its successive ionization energies

The successive ionization energies of an unknown element X are: 1st - 9534; 2nd - 11790; 3rd - 13683; 4th - 15309; 5th - 16458. To what group number does X belong? There aren't any significant ...
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181 views

Does there exist any relation between metallic property and oxidation potential?

I was having a revision on periodic table I was thinking about different properties I could connect most of I could not connect metallic property and oxidation potential .
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301 views

Why is the size of Al3+ less than that of Li+?

Why is it so that the size of $\ce{Al^{3+}}$ is lesser than $\ce{Li+}$? I'm a bit confused about this one as the aluminium(III) ion is composed of 10 electrons and 13 protons, while the lithium ...
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4k views

Why does bond angle decrease in the order H₂O, H₂S, H₂Se?

I know that bond angle decreases in the order $\ce{H2O}$, $\ce{H2S}$ and $\ce{H2Se}$. I want to know the reason. I think this is because lone pair repulsion but how?
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111 views

Arrange B , Be , Li in order of increasing IE2

IE2 = Second ionization energy the correct arrange of them is like this : Be < B < Li ... But why? Li will have the greatest IE2 because that will involve removing a core electron but what I ...
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1k 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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128 views

Atomic radii of Sc,Ti and Fe,Co

The atomic radii of Sc is 162pm , Ti is 147pm , Fe is 126pm and that of Co is 125pm. Electronic configuration of Fe is (Ar)3d6 4s2 and that of Co is (Ar) 3d7 4s2. Difference of Z between them is 1 ...
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121 views

How is the oxidation number related to the group number?

How is an oxidation number of an element related to its group? I was trying to answer an homework question.The question was: If an element X forms the highest oxide of the formula XO3, then it ...
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123 views

Calculating Electronegativity of Fluorine [closed]

Calculate the electronegativity of Fluorine from the following data. EH-H = 104.2 kcal/mol EF-F = 36.6 kcal/mol EH-F = 134.6 kcal/mol XH = 2.1 How to solve? Any wiki or link to somewhere where ...