Questions tagged [periodic-table]

This tag should be applied to questions about the layout, history and interpretation of the periodic table, not to questions relating to specific elements or trends within the table. For these, the tags 'elements' or 'periodic-trends' should be used where appropriate.

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Anomalous Electronic Configuration of Thorium

The electronic configuration of thorium ($Z=90$) is $5\mathrm f^0 6\mathrm d^2 7\mathrm s^2$. But, according to the aufbau principle, the electrons should first enter the $\mathrm f$ subshell and not ...
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5answers
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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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2answers
1k views

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 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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1answer
609 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
209 views

Why do the chalcogens (Y) form YX4, YX6 but not YH4, YH6? [duplicate]

What is it about hydrogen that makes it different from the halides? What makes it only form di- and not tetra- or hexa- hydrides of the chalcogens?
3
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0answers
54 views

What explains the very high density of osmium and iridium? [duplicate]

Iridium with a density of $22.56$ g cm-3 & osmium with $22.59$ g cm-3. Data from their respective Wikipedia pages. Only these two naturally occurring elements have such a high density. I wish to ...
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1answer
3k views

What are inner core electrons and how do they influence chemical and physical properties?

There are six groups of p–block elements in the periodic table numbering from 13 to 18. Boron, carbon, nitrogen, oxygen, fluorine and helium head the groups. Their valence shell electronic ...
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0answers
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How do I know the valence number by looking at the groups? [duplicate]

Groups say the valence number. For example Hydrogen is on group 1, has 1 electron on it's last and only level. So we can know the valence number on that are on the groups 1-2 and 13-18. But how am I ...
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1answer
217 views

Relativistic effects in element 137 (Feinmanium) and above

Here I saw that if an element above atomic no 137 has to exist, it must have electron speed greater than speed of light. My question is , has this calculation been done keeping in mind Einstein's ...
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How do I model atoms with Moebius strips?

This question came to me while I was trying to model the list of elements (Mendeleïev), especially their masses and number of electrons. It came to my mind that it might be easier to model each ...
3
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1answer
610 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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0answers
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Families of some columns [closed]

From previous lessons, I know that column 1 are alkali metals, column 2 are alkaline earth metals, column 3 till column 12 are transition metals, column 17 are halogens and column 18 are inert gases. ...
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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
853 views

Why don't Schools follow latest IUPAC for naming groups?

In high school I am taught that Group 7 were halogens and Group 8 were noble gases, and Group 3 the boron group, Group 4 was carbon group, etc. Then when I looked up the groups, I found that noble ...
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1answer
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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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2answers
940 views

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
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Confusion with the Periodic Table

The periodic table has 7 periods and they have 2,8,8,18,18... elements respectively from 1 to 7. But from what I understand, the periods each state the number of electron shells that the elements in ...
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2answers
40k views

Is aluminium a metal or metalloid?

Aluminium is along the dark line of the Periodic Table and it is $p$-block metal. Is it metal or a metalloid? Why?
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2answers
8k views

Are the elements lanthanum and actinium considered to be in the d block or the f block of the periodic table?

Many periodic tables place lanthanum and actinium in the f-block of elements, for example, this periodic table from Los Alamos National Laboratory. However, this table from the Royal Society of ...
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2answers
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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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1answer
486 views

Periodic table groups - which grouping is “right”? [closed]

In searching online, I've noticed there are a lot of different ways to group the elements of the periodic table. Take mercury in the two tables linked below, for example: http://i.telegraph.co.uk/...
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3answers
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Is there an abundance threshold of a 'synthetic' element for it to be considered natural?

I always (possible naively) thought that elements are either natural or synthetic, either one or the other. But, according to the Wikipedia page about Synthetic Elements, it states that: All ...
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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
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How come uranium's relative atomic mass is 238.03 when it only contains isotopes with a mass number of 238 or less?

I have always been led to understand that the mass of an element on the periodic table is the weighted average atomic mass over all naturally occurring isotopes. This seems to make sense with all the ...
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2answers
346 views

Why isn't helium always He 1s?

Part 1: According to what I've learned so far, helium is in the first row of the periodic table, so its $n$ should always equal $1$. However, a question in my text asks about helium 2s. What is helium ...
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2answers
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What do the numerals on the top right corner of the cells in the periodic table represent?

On the table published here (link) each cell has one to five numerals arranged vertically in its top right corner. The sum of those numbers is always the relative atomic mass of the element. I suspect ...
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1answer
748 views

Reading number of outer shell electrons and other properties from periodic table?

How can one read from the periodic table the number of outer shell electrons that an atom has, to predict how these atoms will make bonds with other atoms? For example to see that hydrogen ($\ce{H}$) ...
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1answer
129 views

Organisation in Periodic table [duplicate]

Why do we find big spaces in the periods of the Periodic Table between $\ce{H}$ and $\ce{He}$, $\ce{Be}$ and $\ce{B}$, and $\ce{Mg}$ and $\ce{Al}$? What is the logic of such organization of the ...
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1answer
24k views

How to find density of element metals

I was wondering, how do I determine what metal (element) has the highest density by using the periodic table? Is it possible?
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1answer
139 views

What exactly is Indium's ability to stabilize non-ferrous metals?

I was reading the History section about Indium on Wikipedia when I came across the following sentence: In 1924, indium was found to have a valued ability to stabilize non-ferrous metals, which was ...
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1answer
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Is there a common name to refer to the groups 13 and 14?

The group 15, 16, and 17 are called the pnictogens, chalcogens, and halogens respectively. Is there a name for the groups 13 and 14 as well?
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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
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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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1answer
112 views

Trying to figure out what these elements have in common [closed]

I have an old periodic table and I marked five metals from groups 1A and 2A with dots to indicate something about them. Only all this time later I can't figure out what exactly it was. I've been ...
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1answer
386 views

Why does the “gap” between atomic radii get smaller down the periodic table?

The question asks: why is the difference in atomic radii between $\ce{K}$ and $\ce{Na}$ larger than the difference in atomic radii between $\ce{Cs}$ and $\ce{Rb}$? I do have some kind of notion that ...
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1answer
342 views

Determine most electronegative element based on successive ionization energy data

X, Y and Z are three unknown elements whose first 5 ionization energies are given below. Which of the 3 is the most electronegative?$$ \begin{array}{|c|c|c|c|c|c|}\hline &\text{IE}_1&\text{IE}...
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1answer
753 views

Reaction between elements in a periodic table [closed]

Can we know the reaction between any two elements in the periodic table? If yes then can we know the reaction between any three or more elements in the periodic table?
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1answer
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Why does potassium form peroxides but sodium does not?

As we go down the periodic table, Group 1 alkali metals hold their single outer valence electron more loosely, and so reactivity increases. Below potassium (Na, Li), we can store the metal in oil with ...
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8answers
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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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3answers
4k views

Periodic table for printing

I there a Good Version of a printable Periodic table Which is minimalistic and gives necessary information only such as - At. Number Element Name At. weight Shell configuration color coding of ...
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1answer
7k views

Actinides and Lanthanides group

I would like to ask which group do actinide and lanthanide belong? I had a question in my assingment that which group has most number of elements? if they belong to 3rd group then the 3rd group should ...
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1answer
504 views

Is it possible to form a divalent transition metal ion that has neither s- nor p-shell valence electrons? [closed]

Can a transition metal ion with a charge of 2+ form without valence shell s and p electrons?
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Why are d-orbitals required/used for hypervalent molecules (where the central atom has expanded its octet) [duplicate]

Period 2 elements like carbon, oxygen and nitrogen cannot expand their octet because they cannot make use of d orbitals in that energy level (they don't exist). However, period 3 elements like sulfur ...
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2answers
189 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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2answers
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Why do heavier elements have smaller specific heat values.

In the periodic table the trend is that as the mass of each element increase's the specific heat tends to go down. This seems to be counter-intuitive because if I am not mistaken as mass increase's ...
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3answers
390 views

What is the usage of orbitals more complex than f orbitals?

Every high school learner, in each corner of the world, faces the lesson History of Atom during his courses, just as I did. We learned about s, p, d and f orbitals, though there were no signs of ...
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1answer
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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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1answer
569 views

Show which group the element with Z=31 belongs

and I understand it belongs to the 13 th group, but my teacher wants to express it as IIIA, so how should I convert it in my mind?
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1answer
353 views

How can we confirm the number of protons in an atom?

The periodic table tells us that there are 6 protons in a carbon atom. Is there a way to verify this first-hand? Or are we just expected to believe it unquestioned?