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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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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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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3k views

Why magnesium has the lowest melting and boiling point in its group? [duplicate]

It is written in the third point ( shown in the picture) that presence of d orbitals results in stronger metallic bond. 1) We check the strength of metallic bonding to compare the melting and boiling ...
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On a periodic table it shows that Zn and Cd and Hg all have 0 electron affinity. Why is that?

Question On a periodic table it shows that Zn and Cd and Hg all have 0 electron affinity. Why is that? What I've noticed I've noticed that these three elements are the end of the D orbital and they ...
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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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How to determine the valence electrons of D-block elements in their mono atomic form?

For s and p block we can determine the valence electrons easily,but what about d-block elements. How to determine their valence electrons?
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Which is the most reactive element in the periodic table? [duplicate]

Which is the most reactive element in the periodic table? Is it francium, caesium, lithium or fluorine?
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Why is caesium considered the most reactive element and not fluorine? [closed]

Some people say caesium is most reactive element. I thought it to be fluorine as it is the element that reacts with almost all elements (except couple of inert gases). But caesium won't react many of ...
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Why does sulfur exist as octasulfur? [duplicate]

Sulfur belongs to the same group as oxygen. Then why oxygen exists as an $\ce{O2}$ molecule while sulfur exists as $\ce{S8}$ molecule? What's the chemistry behind this?
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Melting Point Trend For Non Metals?

I noticed that the melting point for non metals decreases across a period (i.e. melting point of nitrogen is higher than oxygen, oxygen's is higher than fluorine, so on). It is significantly more ...
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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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Trend in atomic radius for noble gases

In an exam, we were given the following graph and asked to explain why the slope of the change in r vs. Z changes dramatically at a point along the curve. I understand that the d block causes the ...
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3answers
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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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Shielding effect- specifically defined?

In all the sites I have searched, shielding effect has been defined as the reduction of the nuclear attraction upon the outer electron/electrons, due to the core electrons that repulse the outer ...
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Reason for decreased boiling point of hexafluoroisoproponal?

Ethanol and isopropyl alcohol have boiling points 78.37 °C and 82.6 °C respectively. The increase in the boiling point is obvious due to increase in carbon chain length which resulted in increase in ...
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Meaning of charges in a group?

In my class, my professor said that since hydrogen is in group one, it has a charge of 1+. Does this refer to its ionic charge or to its oxidation state?
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891 views

As we go down a fluoride-alkali metal series, why doesn't the boiling point decrease?

As you can see from the graph below, as we go down the blue fluoride-alkali metal series (alkali metal ion is varied from Lithium to Rubidium, which is represented by an increase in ionic mass on the ...
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Why is the periodic table periodic?

I am not a chemist, but I am interested in Science in a general sense. Can anybody explain why the periodic table is periodic in nature? I would appreciate links for further reading.
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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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Why does cobalt have a higher atomic mass than nickel?

I understand that this deviation from the general trend of increasing atomic number and atomic mass is because cobalt's isotopes tend to have more neutrons than nickel's. Why is that the case? How ...
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Why is the ionic radius of Al(3+) smaller than that of Li+?

I was examining the ionic radii of some ions from this site for a school assignment. I noticed a weird anomaly in the ionic radius of $\ce{Li+}$ as compared to that of $\ce{Al}^{3+}$. The ionic ...
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Periodic table and p block elements

I have two questions: It's said that in p block there's gradation in physical and chemical properties of elements. What is meant by this statement? Why are the different blocks named s, p, d and f?
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Alkali metal hydrides

I know that stability of alkali metal hydrides decreases down the group,Hence the lowest member in the group easily breaks into its cation but does this easiness of breaking into cation has any ...
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About ionic bonds (and ionic compounds) [closed]

I have a few questions: All ionic bond occurs between a metal and a non-metal. Is this true? In the definition of metal and/or non-metal are the metaloids included? In the definition of non-metal are ...
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Why does electronegativity generally increase across a period? [duplicate]

I've been doing some research and the only answer I seem to be getting is that the increase of protons means electrons are more attracted to the atom. I thought though it was because as you go ...
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299 views

why are mercury gas and tungsten filament used in electric bulbs instead of fluorine which has higher electron affinity?

Fluorine has greater electron affinity than mercury or tungsten and hence fluorine could have been in electric bulbs.Because it can attract electrons easily than the metals which mostly repel extra ...
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The most variant groups of periodic table

Is it okay to call group 11 (formerly 1B) a "group"? I meant that according to my knowledge "A group is a horizontal column consisting of elements with similar valencies and a continuous gradation 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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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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1answer
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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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Does increasing electronegativity imply more covalent character?

If there is a larger electronegativity difference between two atoms, shouldn't the compound be more ionic? In an explanation of the diagonal relationship, it states that "on moving across the period, ...
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871 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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Why is the melting point of magnesium anomalous? [duplicate]

The melting and boiling points for the Group II elements are as follows: $$\begin{array}{ccc} \text{Element} & \text{Melting point / }\mathrm{^\circ C} \\ \hline \ce{Be} & 1289 \\ \ce{Mg} &...
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What is the correct order of chemical reactivity in terms of oxidising property for the following elements: F, Cl, O, and N

This is a textbook question. I am confused as to which factors i should consider while sorting out these elements. If I take electron gain enthalpy, then Cl should be greater than F, but if i consider ...
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1answer
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Bond Type of Lead: Metallic or Network Covalent?

I know that lead is classified as a metal, from its appearance, nonexistent band gap, and its position on the periodic table... etc. However, all of the elements above it (carbon, silicon, germanium, ...
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Melting temperature and electronegativity trends in transition metals [duplicate]

So I know that generally the melting temperature increases across the row (let's look at just the first row for now) but what are the deviations? And why do they occur? I've looked everywhere online ...
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673 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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Deviation of Ytterbium from general trend

What is the reason for deviation of ytterbium from the general trend of lanthanides in terms of hardness, melting point, density etc.?
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Why ground-state configuration is consistent ("additive") from one element to the next?

Ground-state configuration ("electron shells") is consistent throughout the periodic table, for example: (source) Why is it this way if the Hamiltonian of each atom is different? In other words, why ...
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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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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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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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Why is Aluminum's 2nd ionization energy higher than Silicon's?

According to the periodic table trend for I.E. Silicon should have a higher 2nd ionization energy than Aluminum so I'm confused.
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Why does ionization increase from Li to Be? [duplicate]

If ionization energy decreases from $\ce{N}$ to $\ce{O}$ due to the pairing of electrons (causing electric repulsion and greater potential energy) in the $\mathrm{2p}$ orbital in the $\ce{O}$ atom, ...
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742 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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Why ionic radii of Cu2+ is less than Zn2+?

Fully filled orbital has more effective nuclear charge than incompletely filled orbital. So atomic or ionic radii of elements or ions having fully filled orbitals should be less than that of elements ...
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Basicity of Group 15 hydrides [duplicate]

Why does the basicity of Group 15 hydrides ($\ce{NH_3,~ PH_3,~ etc}$) decreases down the group ? I know that's because of its Lewis Base nature due to the lone pair but wouldn't the more EN element ...
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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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Solubility of Noble Gases

I read this statement that: Xenon is the most soluble noble gas in water. My first doubt is: Why does the solubility of noble gases in water increase down the group? Even if this is the trend, ...

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