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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9
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1answer
13k views

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
721 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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1answer
2k views

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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1answer
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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 ...
4
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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? ...
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Why is ionisation energy of bismuth lower than lead?

Why is ionisation enthalpy of Bismuth less than that of Lead for it just comes after the latter in periodic table? First ionisation energy of bismuth is 703 kg/mol while that of lead is 715 kg/mol. I ...
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Why do the melting points of Group 15 elements increase upto Arsenic but then decrease upto Bismuth?

The boiling points of group 15 elements increase on going down the group (or, as size increases) but the same is not true for the melting points. The melting points increase from $\ce{N}$ to $\ce{As}$ ...
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1answer
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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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848 views

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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Ionization energy and Electron Affnity

Which of the following statements correctly interprets the relationship between ionization energy, atomic radius Electron affinity when comparing two atoms. The correct choice as per my instructor ...
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1answer
8k views

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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2answers
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Memorizing polyatomic ions? Using Periodic Table

In my Chemistry course, we must memorize a list of common polyatomic ions. Is their an easy way of memorizing ions such as Sulfate $\ce{SO4^2-}$ by looking at just the periodic table. I listed the ...
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1answer
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Is it possible that atoms with 120 protons are possible, but that atoms with 119 protons aren't possible?

We currently know that there are atoms with atomic number up to 118 are possible. Is it possible that atoms with 120 protons are possible, but that atoms with 119 protons aren't possible? Or are ...
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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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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 is lutetium part of the lanthanide series?

I’ve been looking at the periodic table and began to wonder - why is lutetium part of the lanthanide series? Or, for that matter, why is lawrencium part of the actinide series? This isn’t readily ...
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Instability of heavy hydrides

Question: Why do hydrogen compounds from the third period down (that are electron deficient or have completed octets) readily decompose? Thoughts: Apparently, heavier group 14 elements form ...
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2k views

Why there is an exception in melting and boiling point in p block?

Why is the boiling point and melting point of 15th group and 16th group has an exception? We know that as molecular mass increases boiling point and melting point also increase. So, down the group 15 ...
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3answers
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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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7answers
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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 $\ce{Al2Cl6}$ as there are in $\ce{B2H6}$?
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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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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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2answers
28k views

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

We have to select the set of elements which will have almost the same atomic radii: $\ce{O, S, Se, Te}$ $\ce{Li, Be, B, C}$ $\ce{Fe, Co, Ni, Cu}$ I googled the atomic radii of the third set and ...
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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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1answer
8k views

Why does color of halogen deepens and the boiling point decreases down the group?

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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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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Trend in the melting point down the group

We know that the atomic radii increases down the group. So, less energy is required to pull out the outermost electron as we go down the group, hence, gradually melting point decreases down the group....
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1answer
11k 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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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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1answer
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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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1answer
34k 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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2answers
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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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1answer
7k 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 second period, The graph is pretty steep ...
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1answer
255 views

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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1answer
9k views

“Middle row anomaly” of the periodic table

I was studying about the periodic table recently, and was reading a topic associated with oxides of halogens, and came across the following line The bromine oxides, $\ce{Br2O}$, $\ce{BrO2}$, $\ce{...
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1answer
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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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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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1answer
2k 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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Why is lithium the most reducing alkali metal, and not caesium?

Caesium has a larger size, and the effective nuclear charge that the valence electron experiences will be far less compared to that of lithium's, right? But lithium is still considered the strongest ...
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1answer
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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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1answer
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!
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370 views

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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1answer
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Why does the second electron affinity has an opposite sign of the first one?

Many first electron affinities are positive, indicating a favourable process, but the corresponding second electron affinities are negative. For example, the first and second electron affinities of ...
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2answers
4k views

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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1answer
6k 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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201 views

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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