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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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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111 views

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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Reducing character of group 15 hydrides

It was given in my text book that reducing character of group 15 hydrides increases down the group. I am a bit confused about this. For $\ce{NH3}$ this is fine as I assume that: $$\ce{NH3 -> N + H^...
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246 views

Finding electron configuration by following the Aufbau principle

In the question, "Electron Configuration of Tellurium", there is mention of the 'follow yellow brick road' method of finding electron configuration. What I'd learned in the past was to find the ...
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Bond length increase when replacing nitrogen with phosphorus for NH3 and NF3

There is an increase in bond length of about $40\rm~pm$ from $\ce{NH3}$ to $\ce{PH3}$, but only by about $20\rm~pm$ from $\ce{NF3}$ to $\ce{PF3}$. I understand that the bond length will increase with ...
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What is an 'acidic' oxide?

My book says that: Oxides in higher oxidation states of elements of group 14 are generally more acidic than those in lower oxidation states.The dioxides $\ce{CO2}$, $\ce{SiO2}$ and $\ce{GeO2}$ are ...
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23k views

Variation in atomic sizes in the transition elements

From left to right across a period, effective nuclear charge increases in the transition series, just like in the p block, and so atomic size decreases. Here the electrons are being added to the d ...
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933 views

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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Why do alkali metals have an exothermic electron affinity?

Alkali metals should have positive electron gain enthalpy as they are electropositive elements and also there atomic size is big in their periods so they should be reluctant to take electrons but they ...
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156 views

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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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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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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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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356 views

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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In the periodic table, why doesn't the 2nd row have exactly 2 elements?

Row 1: 2 elements Row 2: 8 elements Row 3: 8 elements Row 4: 18 elements Row 5: 18 elements Row 6: 32 elements Row 7: 32 elements In other words: 2, 8, 8, 18, 18, 32, 32 Why does the first row ...
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On the periodic table: Why are groups of elements organized by 'letter' [duplicate]

Why are the groups of elements on the periodic table organized into areas represented by the letters s,p,d,f,g, and h? What does this mean?
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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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Which of the following statements is true about the trend down group 7?

Which of the following statements is true about the trend down group 7 (halogens) with increase in atomic number? The reactivity increases. The atoms get smaller The boiling points ...
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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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If fluorine has a lower electron affinity than chlorine, why does it have a higher ionization energy?

I have read that fluorine has a lower electron affinity than chlorine despite its lower atomic radius because its electron cloud is extremely dense. If this is the case, shouldn't the ionization ...
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1answer
651 views

How long the block starting with element 121 will be?

I remember from my chemistry classes that (after the initial irregularities) a new block of elements starts every two periods. After the initial s-block and p-block following it shortly, we have d-...
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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 are elements on the right side of the periodic table nonmetallic and gas at room temperature?

Elements on the left side of the periodic table tend to be solid and metallic, elements on the right side of the periodic table are nonmetal and tend to be gases at room temperature, and the semi-...
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Why is Mo(VI) more stable than Cr (VI)?

Acids of $\ce{Mo}^\mathrm{VI}$ are more stable than those of $\ce{Cr}^\mathrm{VI}$ in terms of redox reactivity. In p-block elements, as we go down the groups, the stability of lower oxidation state ...
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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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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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Order of positive mesomeric effect of halides

I learned that the order of $+M$ effect (mesomeric effect) for halogens is as follows: $\ce{F} > \ce{Cl} > \ce{Br} > \ce I$. I wonder why this is so?
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How well do d-block electrons actually shield?

I've been using 'Chemical Structure and Reactivity: An integrated approach' by James Keeler and Peter Wothers to study periodicity, among other sources. However, there seem to be some commonly ...
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895 views

Is using melting/boiling point good to measure volatility?

I wanted to figure out a way to compare volatility in organic compounds, so I read on many forums on the differing ways to measure volatility, which included enthalpy of vaporization and melting/...
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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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Oxidation state of Halogens

So the question is which is the most common oxidation state of halogens and I have to justify my answer. Is my following thought correct? Do I have to add something? The most common oxidation state ...
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153 views

Which hydrogen halides react with group 14 oxides?

$$\ce{6HF +SiO2->H2SiF6 +2H2O}$$ $\ce{HF}$ reacts with $\ce{SiO2}$ to form $\ce{H2SiF6}$. Do other hydrogen halides like $\ce{HCl}$ and $\ce{HBr}$ react with group 14 oxides in the same way?
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Periodic table- quantum numbers

I have come across many questions like: "if electron had 3 spins (-1/2,0,+12) then what change will be there in the periodic table?", also sometimes " if the capacity of each orbital becomes 5 then in ...
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381 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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619 views

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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280 views

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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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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191 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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Non existence of B3+ in solution [closed]

I read that B3+ ions do not exist in aqueous solution, because hydration energy cannot compensate for the sum of first three ionisation energies. This leads me to the following questions: If boron (...
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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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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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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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Inert Pair Effect [duplicate]

My notes say that inert pair effect is the tendency of electron in the outermost atomic s orbital to remain unionised or unshared in compounds of post-transition metals. (Eg. Sncl2 is formed ...
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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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Why are alkali salts so soluble?

There's a certain solubility rule stating all carbonates, phosphates and hydroxides are insoluble unless mixed with hydroxides or alkali metals. Why is this? What makes the alkali metals so special?
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Good collection of images showing periodicity of the Table?

Mendeleev's recognition of the periodicity of atomic trends was a milestone of human understanding, the detection of a pattern in what had appeared to be chaotic data. I think the significance and ...
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Why does electronegativity increase as effective nuclear charge increases?

I know that electronegativity is the ability to attract shared electrons and that effective nuclear charge is the pull of the nucleus on outer electrons based on my notes. But I'm not really sure ...
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500 views

Why several of isomers of octane such as 2,3-dimethylhexane and 2,4-dimethylhexane doesn't have a value for melting point from any databases?

This is a very rough data (as shown below) I have collected from CRC Handbook of Chemistry and Physics 93rd edition in black and ChemSpider in blue. As you can see, I am not quite done, but I was ...
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Why is the melting point of hydrogen iodide larger than that of hydrogen fluoride?

Compare the melting points of hydrogen fluoride (HF) and hydrogen iodide (HI). I know the following things: $\ce{HF}$ melts at $189.6~\mathrm{K}$ and $\ce{HI}$ at $222.35~\mathrm{K}$. There are a ...
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2k 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!