The periodic table is a system in which elements are organized on the basis of their atomic numbers, electron configurations, and recurring chemical properties.
Several scientists, Newland, Doberneir, Meyer, Mendeleev..among others, tried to come up with such a system.
Mendeleev came up with the first widely recognized periodic table in which he arranged elements in horizontal rows and vertical columns and grouped elements with similar chemical properties together.
As the story goes, the idea for his periodic table struck Mendeleev when he was playing with himself (playing cards, you perv..a game called solitaire or patience).
Mendeleev concluded that chemical properties of an element are a periodic function of their atomic masses. He also predicted the existence of germanium, gallium and scandium.
Sure there were a few issues with his work.
Problems:
But his system worked well (for the most part) and he had an awesome beard, and he has a brand of vodka named after him..so he gets the The Passive Observer seal of approval.
The modern periodic law differs from Mendeleev's and states that chemical properties of an element are periodic functions of their atomic number.
In the modern periodic table (pictured below) the rows are called "periods" and the columns are called "groups"
Groups 1 and 2 (alkali metals and alkaline earth metals) constitute the s-block with their valence electrons occupying the s-orbital. Their outer electronic configuration is ns1-2
Groups 13-18 constitute the p-block. Their outer electronic configuration is ns2 np1-6
Groups 3 to 12 constitute the d-block (also called the transition elements) and are characterized by the filling of inner d-orbitals. These elements have the general outer electronic configuration (n-1)d1-10 ns0-2
Quick-Tip: Think Power Rangers.
Now look at the dismembered two rows, the lanthanoids and actinoids, they are called the f-block or inner transition elements and their general outer electronic configuration is (n-2)f1-14(n-1)d0-1 ns2
Quick Tip: Count from the nearest noble gas.
For instance, if I asked you to locate Bismuth, atomic no. 83 (and well no peeking at the periodic table)
The closest noble gas happens to be Radon, atomic no. 86, located in period 6 group 18. Therefore bismuth, atomic no. 83 is present in period 6 and group 15 (moving 3 spaces back).
Let's try Silver, atomic no. 47. (again don't sneak a peek at the periodic table). The nearest noble gas happens to be Xenon, atomic no. 54, which is located in group 18 period 5. Therefore Ag is present in period 5, (and moving back 7 spaces) group 11.
Number of Elements in a Period
Each row (period) corresponds to the filling of a new energy level.
In the first period, n=1 and the 1s orbital is filled. Since the 1s orbital can accomodate a total of 2 electrons, the first period also houses 2 elements (H and He)
Similarly for the 7th period , the following orbitals are available 7s 5f 6d 7p and it can accommodate a total of 32 elements.
Hydrogen and Helium
Hydrogen has one s-electron and can be placed in group 1 with other alkali metals. Hydrogen can also gain an electron to attain stable gas configuration and thus at times behaves like group 17 (halogens) elements.
Helium, has the electronic configuration 1s2 and strictly speaking should be a part of the s-block, but since it has a completely filled valence shell its chemical properties are akin to those of other group 18 (noble gases) elements.
Nomenclature of Elements with Atomic Number Greater than 100
Ready-Reference Chart
Digit Name Abbreviation
0 nil n
1 un u
2 bi b
3 tri t
4 quad q
5 pent p
6 hex h
7 sept s
8 oct o
9 enn e
________________________
That's all folks!
Stay tuned for a follow-up post on periodic trends.
till then, The Passive Observer Out
Several scientists, Newland, Doberneir, Meyer, Mendeleev..among others, tried to come up with such a system.
Mendeleev came up with the first widely recognized periodic table in which he arranged elements in horizontal rows and vertical columns and grouped elements with similar chemical properties together.
As the story goes, the idea for his periodic table struck Mendeleev when he was playing with himself (playing cards, you perv..a game called solitaire or patience).
 |
| click to enlarge |
Sure there were a few issues with his work.
Problems:
1. Mendeleev couldn't account for the isotopes of an element. (isotopes of an element have the same atomic number but different atomic masses.). For example, an isotope of carbon is 14C. This would have to be accommodated along with nitrogen. But 14C shows properties similar to those of carbon (12C).
2. In order to ensure that elements in a column have similar chemical properties, Mendeleev was forced, in a few cases, to put an element of slightly higher atomic weight ahead of one of slightly lower atomic weight. Thus, tellurium (atomic weight 127.6) had to be put ahead of iodine (atomic weight 126.9) in order to group Iodine with other halogens on the basis of similar chemical properties.
But his system worked well (for the most part) and he had an awesome beard, and he has a brand of vodka named after him..so he gets the The Passive Observer seal of approval.
The modern periodic law differs from Mendeleev's and states that chemical properties of an element are periodic functions of their atomic number.
In the modern periodic table (pictured below) the rows are called "periods" and the columns are called "groups"
 | |
|
Groups 1 and 2 (alkali metals and alkaline earth metals) constitute the s-block with their valence electrons occupying the s-orbital. Their outer electronic configuration is ns1-2
Groups 13-18 constitute the p-block. Their outer electronic configuration is ns2 np1-6
Groups 3 to 12 constitute the d-block (also called the transition elements) and are characterized by the filling of inner d-orbitals. These elements have the general outer electronic configuration (n-1)d1-10 ns0-2
Quick-Tip: Think Power Rangers.
 |
| Whoever came up with this system, must've been a fan of this show |
Now look at the dismembered two rows, the lanthanoids and actinoids, they are called the f-block or inner transition elements and their general outer electronic configuration is (n-2)f1-14(n-1)d0-1 ns2
Locating an element
Quick Tip: Count from the nearest noble gas.
For instance, if I asked you to locate Bismuth, atomic no. 83 (and well no peeking at the periodic table)
The closest noble gas happens to be Radon, atomic no. 86, located in period 6 group 18. Therefore bismuth, atomic no. 83 is present in period 6 and group 15 (moving 3 spaces back).
Let's try Silver, atomic no. 47. (again don't sneak a peek at the periodic table). The nearest noble gas happens to be Xenon, atomic no. 54, which is located in group 18 period 5. Therefore Ag is present in period 5, (and moving back 7 spaces) group 11.
Number of Elements in a Period
Each row (period) corresponds to the filling of a new energy level.
In the first period, n=1 and the 1s orbital is filled. Since the 1s orbital can accomodate a total of 2 electrons, the first period also houses 2 elements (H and He)
In the second period, n=2. Thus, the 2s and 2p orbitals are
filled. Therefore the 2nd period accommodates a total of 8 elements
(since the 2s and 2p orbitals can together accommodate 8 electrons (6+2) )
Similarly in the 3rd period 3s and 3p orbitals
are filled and it can accommodate 8 elements.
In the 4th period the 4s, 3d and 4p orbitals
(refer to aufbau principle) are filled and it can thus accommodate a total of
2+10+6= 18 elements.
Similarly the 5th period corresponds to the
filling of 5s 4d and 5p orbitals and thus accommodates 18 elements.
The 6th period corresponds to the filling of the
6s 4f 5d and 6p orbitals and can thus accommodate a total of 32 elements.
Similarly for the 7th period , the following orbitals are available 7s 5f 6d 7p and it can accommodate a total of 32 elements.
Hydrogen and Helium
Hydrogen has one s-electron and can be placed in group 1 with other alkali metals. Hydrogen can also gain an electron to attain stable gas configuration and thus at times behaves like group 17 (halogens) elements.
Helium, has the electronic configuration 1s2 and strictly speaking should be a part of the s-block, but since it has a completely filled valence shell its chemical properties are akin to those of other group 18 (noble gases) elements.
Nomenclature of Elements with Atomic Number Greater than 100
Ready-Reference Chart
Digit Name Abbreviation
0 nil n
1 un u
2 bi b
3 tri t
4 quad q
5 pent p
6 hex h
7 sept s
8 oct o
9 enn e
________________________
That's all folks!
Stay tuned for a follow-up post on periodic trends.
till then, The Passive Observer Out
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