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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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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1answer
11k views

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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55 views

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 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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1answer
480 views

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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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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3answers
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Which has the largest bond angle between water, oxygen difluoride and dichlorine oxide?

Which one out of $\ce{H2O}, \ce{Cl2O}, \&\ \ce{F2O}$ will have largest bond angle? I think it should be $\ce{H2O}$ because oxygen is most electronegative in this case so electrons will be more ...
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1answer
885 views

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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1answer
2k views

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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1k 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 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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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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1answer
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Melting points of alkali metal halides

The correct order of melting point of alkali metal halides is: $\ce{MF}>\ce{MCl}>\ce{MBr}>\ce{MI}$ $\ce{MI}>\ce{MBr}>\ce{MCl}>\ce{MF}$ $\ce{MCl}>\ce{MF}>\ce{MBr}>\ce{MI}$ $\...
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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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90 views

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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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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Relation of Boiling Point and Melting Point with the reactivity of an element

When we look at the trends of periodic table, there is an interesting correlation to be noticed. Along a period, when we look at the trends in reactivity of an element( Both due to electropositivity ...
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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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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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100 views

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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327 views

On the oxyacids of +III pnictogens and +IV chalcogens

Phosphorus in its $\mathrm{+III}$ oxidation state is known to exist as the phosphonic acid tautomer rather than phosphorous acid one. All salts isolated containing $\ce{H2PO3-}$ are (to the best of my ...
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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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1answer
4k views

Comparing radii in lithium, beryllium, magnesium, aluminium and sodium ions

Apparently the of last four, $\ce{Mg^2+}$ is closest in radius to $\ce{Li+}$. Is this true, and if so, why would a whole larger shell ($\ce{Mg^2+}$) be closer in radius to $\ce{Li+}$ than its ...
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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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305 views

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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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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How does increasing the molecular mass of compounds of homologous series affect solubility?

First of all, I know that increasing the molecular mass decreases the solubility of that compound wrt, of another compound of the homologous series in organic chemistry. My question is how? My text ...
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1answer
2k views

2nd Electron Affinity of halogens

I have seen questions regarding EA but they were all about the 1st EA so this question is not duplicate. I came across a statement which goes like "2nd EA of halogens is almost zero". How is this ...
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1answer
1k views

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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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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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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185 views

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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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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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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Increasing Covalent character increases Colour intensity

I observed some trends as follows:- $\ce{PbCl2}$ white and $\ce{PbI2}$ yellow $\ce{SnCl2}$ white, $\ce{SnCl4}$ red and $\ce{SnI4}$ black $\ce{AgCl}$ white, $\ce{AgI}$, $\ce{AgBr}$ and $\ce{Ag2CO3}$ ...
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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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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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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 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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Why is fluorine more reactive than iodine despite the weaker I-I bond?

The atomic radius of halogens increases as we go down the group due to the addition of new shells. As a result, the bond length of halogen $\ce{X-X}$ increases down the group. So, less energy is ...
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1answer
716 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 does tin form tin (II) compounds?

The stability of the +II oxidation state in lead has been widely attributed to the so-called “inert pair effect”: the 6s subshell is stabilized through relativistic contraction due to the near-c speed ...
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Why do the boiling and melting points decrease as you go down group 1 and vice versa for group 7?

I used to think that because an alkali metal needs to lose one electron to complete its outer shell, when the atom increases in size (atomic radius), the electron would be easier to lose as the ...
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1answer
6k views

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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2answers
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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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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? ...