Friday, July 29, 2011

Hydroxides Nomenclature

Hydroxides are a group of compounds not well known in general, although you might know them by their commercial name in some cases.

Copper Hydroxide
                
Sodium Hydroxide
 
Some Hydroxides are present on drain cleaners; some are used on making soap and detergents.
Hydroxides are formed when Metal Oxides react with Water.

CaO + H2O ---> Ca(OH)2

Hydroxides have this writing structure:

Metal OH

And like with Oxides we just need to figure out the subscripts A,B.

MetalA (OH)B

For Hydroxides the (OH) radical works with -1. Now you write the oxidation number of the metal and the valence of the OH radical.
Now you just have to SWITCH the numbers like this and you are done, know you know how to make Hydroxides. Metal oxidation numbers can be found here
Never write the subscript of the OH radical WITHOUT ( ).
HYDROXIDE NOMENCLATURE

There are 3 ways of naming Hydroxides.
  • TRADITIONAL nomenclature
  • IUPAC nomenclature
  • STOCK nomenclature

TRADITIONAL NOMENCLATURE

You need to learn a little system of prefixes and suffixes (for the oxidation numbers)
  • If it only has 1 oxidation number there isn’t a suffix to use, some people use the –ic suffix.
  • If it has 2, the higher is –ic and the lower is –ous.
-ous
-ic
+2
+3
+1
+2
Note that the suffix does not depend on the number but on how many valences the element has. I’ve seen people making the mistake to think that +2 is always –ous or always –ic.

EXAMPLE

Name this Hydroxide

Fe(OH)3

Remember how to make hydroxide formulas? Now we just need to go backwards to figure out which oxidation number the metal is using.
Now that we know which it is, let’s find the correct suffix to use. It has 1 oxidation numbers:

+2 ----> -ous

+3 ----> -ic

Traditional nomenclature has this writing structure:

[ELEMENT NAME][SUFFIX] Hydroxide

So we just need to fill the name of the metal and the suffix

Ferric Hydroxide

Be careful with some element names, some aren’t use in nomenclature, such as IRON (Fe): so it wouldn’t be IRONIC (heheh), but FERRIC.

IUPAC NOMENCLATURE

This one is the easiest in my opinion, it is also called “systematic”; you just need to learn these prefixes:

Number
Prefix
1
mono-
2
di-
3
tri-
4
tetra-
5
penta-
6
hexa-
7
hepta-
8
octa-
9
nona-
10
deca-
EXAMPLE:

Fe(OH)3

You just need to use the prefixes to name the element according of the subscripts.
 In this case the structure of IUPAC nomenclature is

[PREFIX][ELEMENT NAME]  [PREFIX]Hydroxide

So this is the name of the oxide according to IUPAC Nomenclature (if the metal has a subscript of one we don’t use MONO, we only use MONO if the radical OH has 1 as subscript):

Iron triHydroxide

STOCK NOMENCLATURE

This is an easy nomenclature as well; you don’t have to know anything else but the oxidation numbers of the elements.

EXAMPLE:

Fe(OH)3

First step is to figure out the oxidation number of the metal:
 The structure of STOCK nomenclature is

[ELEMENT NAME][OX. NUMBER]     Hydroxide

The oxidation number of the metal has to be written in Roman numbers (I, II, III, IV, etc.).
This is the name according to Stock Nomenclature:

Iron(III) Hydroxide

Be careful with writing a space between the name and the Roman number, there isn't one.

Coming up! Hydroxides Exercises

Wednesday, July 27, 2011

How to use your Periodic Table (Advanced)

If you want some basic information about the Periodic Table be sure to check here: How to use your Periodic Table (Basic)

I’ve been behind with my post about Hydroxides Nomenclature, but it’s coming soon; for that I apologize.

Let’s go beyond now, like I said that piece of paper called a Periodic Table gives a lot of useful information for your chemist needs, if you don’t have one yet get one Get your own Printable Periodic Table.

I’ve always wanted to know how to make equations and how to predict what reactions could happen with elements. Now with the help of some basic knowledge about Nomenclature and our Periodic Table we can.
Let’s check some properties that can be predicted with our Table

ATOMIC RADIUS

Imagine the atom like a Peach, the seed in the center would be the nucleus (where protons and neutrons are) and the rest the electrons around it.
The more neutrons, electrons and protons the atom has, the bigger it is. But it’s a little more complicated than that, because there are other properties that come in place when we want to figure out the Radius.

The protons, neutrons and electrons increase this way on the table.
So intuitively you could say that the radius would increase the same way, but the rule is different, mostly because electronegativity plays an important part, higher electronegativity means smaller atom.
The atomic radius increases this way instead.
So basically you can predict which atom is bigger.

ELECTRONEGATIVITY

Electronegativity is the property of atoms to attract/draw electrons into the nucleus, basically is the force of protons(+) attracting electrons(-) closer to the nucleus.
While the atom increases its size with the number of particles, the attraction force makes the electrons layer thinner, it’s like if the peach would have bigger seed but the fruit part is thin.
The electronegativity increases in this way.
ELECTRONS ON THE LAST SHELL

This could be one of the most important information you can get from the table, to understand it you need to know that MOST elements follow a certain rule, they are jealous of the Noble Gases, yeah, not kidding, elements want to look like noble gases because they are stable and non-reactive (is normal conditions).
What’s that special characteristic of noble gases that makes everyone wanting look like them? They have their last Shell FULL, that’s it; they have 8 electrons on the last Shell making them unable to react with other elements (this rule does not apply to all elements; some are weird and hard to understand).

You can find that number here; elements on the same group have the same number of last Shell electrons (they are on Roman numbers)
But how would elements would try to look like noble gases??? The only way is losing or gaining electrons, but this is only a fail attempt that gases laugh at, it works though.
Electrons increase this way on the table, and elements are listed and must be read this way.
Each time you move 1 square to the right the number of electrons increases by 1, elements will try to look like the noble gas on the same horizontal line.
So Oxygen would try to look like Neon
Or Bromine like Krypton
These elements must gain electrons to gain the “noble status”, oxygen would need to gain 2 or Bromine just 1.

Elements on this side have a problem, the amount of electrons they need to gain is too big, and their electronegativy is low (Check above) so they don’t have enough “strength” to attract electrons.
So they must do it the other way, they will have to try looking like the noble gas of the horizontal line above of them and that means losing electrons.
Sodium would need to lose 1 electron to look like Neon
Calcium gives away 2 to look like Argon
This group here is similar to calcium or sodium group, although the rule of # of electrons on last shell is kinda tricky, I still can’t understand them well but they lose electrons.
REACTIVITY

So basically you have 2 kinds of elements in reactions, some lose electrons and some are willing to take them, this give and take is what makes chemical reactions happen.
You can predict most of Chemical reactions but like I said, you will need the help of nomenclature to fully understand them
Like Oxides: that is a compound made of Oxygen and a Metal or Non-Metal.
Or Hydroxides that have Oxygen, Hydrogen and a Metal
Or Acids that have Oxygen, Hydrogen and a Non-Metal.
Chemical reactions are a little more complicated than just putting elements together, like I said some lose electrons, some gain them, and some SHARE them, most of the compounds are made of atoms that have shared electrons with other atoms to fulfill that need to become stable.

Coming Up!! Hydroxides Nomenclature (This time for real)

Wednesday, July 13, 2011

Get your own Printable Periodic Table

I’ve search around and come across some pretty cool periodic tables, for those who haven’t got one yet, you can now get a nice printable version.
These Tables can be printed out on a large poster for your wall or for the science lab wall, i'm thinking on printing some on T-shirts.

Disclaimer: I haven’t created any of the following tables; all rights are retained by the original authors of them

                                                                                                                                                                                                                                                                      
  • www.periodni.com is a nice source of printable periodic tables (in different LANGUAGES!!) among other material, give them a visit and they might fill your needs.
This is what you can find there.

 
This is a periodic table with basic rules for balancing chemical equations and some constants, it has a ruler aswell.
 



A nice black and white version of the periodic table with basic information; the atomic weights of the elements are rounded to 5 significant figures.
  

 

This is a printable color version; the colors denote the element groups.




For those who want a Periodic Table as desktop feel free to use this one (they have it in other resolutions), to get it just save this image directly.






                                                                                                                                                                                                                                                                      
  •  www.elementsdatabase.com has 2 versions of a basic Periodic Table, very useful for learning the basic characteristics of chemical elements.

Download
Download











                                                                                                                                                                                                                                                                       


  • Mr. Allan is a High school Science teacher; He made 5 of the following tables the rest were gathered by him from different sources. This is his site where you can find the rest of them: http://www.sciencegeek.net
  • These 2 tables are my personal favorite, Dr. Jon Wittwer wanted to "create a table that would pack as much property data onto a single 8 1/2 x 11 sheet of paper as reasonably possible.", I love all the info you can get from it.



Download
Download
 Source: http://www.vertex42.com/ExcelTemplates/periodic-table-of-elements.html
  • These are some of Mr. Allan's creations.
 
Average molar masses are rounded to two decimal places. The table also includes electronegativity values. Element symbols are color coded (black = solid, red = gas, blue = liquid).
 

This a version that is color-coded by element classes, and includes the usual information, but also the atomic radius of each element.
Download




This is a similar version but also the electronegativity of each element.
Download




  • These tables were gathered by Mr. Allan

 
This is the periodic table used with the California Standardized Test in Chemistry. It has 2 sides and the back of the table includes equations and constants.


 
This table shows the ions formed by the elements. It also contains an excellent table of polyatomic ions. It is the product of Joel Weiner, who teaches at Evanston Township High School in Evanston.


A periodic table with color, from the Lawrence Berkeley Laboratory. Includes other useful data such as electron configuration, melting point, boiling point, oxidation states and more.
Download



The black and white version of the Lawrence Berkeley Lab Table
Download



Los Alamos Nuclear Lab provides colorful table. It has a noble-gas configuration notation for each element.
Download




This table is the black and white version of the Los Alamos periodic table.
Download




This table is produced by the Physics Lab at NIST, the National Institute of Standards and Technology. It has a very colorful background.



 
A good basic table from the New York Regents. This black and white table includes electron configurations.




Source: Find more at http://www.sciencegeek.net/tables/tables.shtml

Coming up next!!: Hydroxides Nomenclature

Tuesday, July 12, 2011

Inorganic Reactions: Oxides Exercises

As we saw in my last post, oxides are very easy to name, I need to remark that these aren’t the only compounds where oxygen is, SIMILAR to oxides there are the Anhydride Compounds and they follow the SAME RULES as oxides but are made with NON-METALS.


HALOGENS


ANFIGENS


Fluorine
Chlorine
Bromine
Iodine
F
Cl
Br
I
-1
-1 +1 +3 +5 +7
-1 +1 +3 +5 +7
-1 +1 +3 +5 +7
Oxygen
Sulphur
Selenium
Tellurium

O
S
Se
Te
-2
-2 +2 +4+6
-2 +2 +4+6
-2 +2 +4 +6
NITROGEN GROUP


CARBON GROUP


Nitrogen
Phosphorus
Arsenic
Antimony
Boron
N
P
As
Sb
B
-3  +3  +5
-3  +3  +5
-3  +3  +5
-3  +3  +5
-3  +3 

Carbon
Silicon
C
Si
+4  -4
+4  -4




Coming back to the exercises:

Name these oxides with all 3 nomenclatures:

K2O

Potassium has a valence of +1

Potassium Oxide                    <--- Traditional
DiPotassium Monoxide         <--- IUPAC
Potassium(I) Oxide                <--- Stock

Fe2O3

Iron has a valence of +3 in this oxide

Ferric Oxide                           <--- Traditional
diIron trioxide                                    <--- IUPAC
Iron(III) Oxide                       <--- Stock

Na2O

Sodium has a valence of +1

Sodium Oxide                                    <--- Traditional
Disodium Monoxide              <--- IUPAC
Sodium(I) Oxide                    <--- Stock

CaO

Calcium has a valence of +2

Calcium Oxide                       <--- Traditional
Calcium Monoxide                <--- IUPAC
Calcium(II) Oxide                 <--- Stock

Cr2O3

Chromium has a valence of +3

Chromic Oxide <--- Traditional
DiChromium Trioxide<--- IUPAC
Chromium(III) Oxide<--- Stock

Tuesday, July 5, 2011

Inorganic Reactions: Oxides Nomenclature

Oxides, in most industries this is the worst thing you could see, this is a sign of time taking its share out of metals.



But let’s take a look at our beloved elements first; to study oxides first we have to learn the oxidation numbers of some of the main elements.
At first it’s not mandatory for you to learn them all, but in the long term you should.
There are 2 main families of elements, the metals and the non metals families.
Oxygen form Oxides with metals and Anhydrides with non-metals (fancy way to say oxides of non-metals)

MONOVALENT



DIVALENT


Lithium
Sodium
Potassium
Silver
Rubidium
Cesium
Ion Ammonium
Francium
Li
Na
K
Ag
Rb
Cs
NH4+
Fr



+1

Beryllium
Magnesium
Calcium
Strontium
Barium
Radium
Zinc
Cadmium
Be
Mg
Ca
Sr
Ba
Rd
Zn
Cd



+2














TRIVALENT



DI-TRIVALENT


Aluminum
Bismuth
Al
Bi
+3

Chromium
Manganese
Iron
Cobalt
Nickel
Cr
Mn
Fe
Co
Ni
+2 +3














MONO-DIVALENT



DI-TETRAVALENT


Copper
Mercury
Cu
Hg
+1 +2

Lead
Tin
Platinum
Iridium
Palladium
Pb
Sn
Pt
Ir
Pd
+2 +4














MONO-TRIVALENT



Gold
Au
+1 +3





































Those numbers are the MOST COMMON oxidation states of elements, the oxidation state “measures the degree of oxidation of an atom in a substance” according to the IUPAC (International Union of Pure and Applied Chemistry)
The IUPAC has a set of rules for oxidation states, some of them are:

  • The oxidation state of a free element (uncombined) is zero
  • Hydrogen has an oxidation state of 1 and Oxygen has an oxidation state of -2 when they are present in most compounds. (Exceptions to this are that hydrogen has an oxidation state of -1 in hydrides of active metals, and oxygen has an oxidation state of -1 in peroxides)
  • The algebraic sum of oxidation states of all atoms in a neutral molecule must be zero, while in ions the algebraic sum of the oxidation states of the constituent atoms must be equal to the charge on the ion.

OXIDATION AND REDUCTION

OXIDATION DOES NOT mean that the element has been exposed to oxygen. (Even if it sounds like it).
  • OXIDATION: is the loss of electrons by a molecule, atom or ion. 
  
  • REDUCTION: is the gain of electrons by a molecule, atom or ion.
In chemical reactions happens BOTH. If one element is being oxidized, the other is being reduced.

OXIDE FORMATION

Oxides are formed when the metal in its ground state is exposed to oxygen.

4 Al  +  3 O2   ----->    2 Al2O3

In this reaction the element is oxidized and the oxygen reduced.

Al0  ------>  Al+3   Oxidation
O0   ------>  O-2     Reduction

For teaching purposes you don’t need to know how to make the chemical reactions, but just the final compound.
Compound formulas have 2 main parts:
This is why I told you to learn the abbreviation and oxidation numbers of elements.
This is the correct way to write oxides.

[METAL]O

Now we just need to know how to figure out the subscript A,B of the atoms (the subscript tells us how many atoms of that element is present in that molecule)

[METAL]AOB

For OXIDES the oxygen always has an oxidation state of -2 (don’t forget this), and depending of the metal or non-metal there can be many options for compounds.
First you write the oxidation number:
Now you just have to SWITCH the numbers like this and you are done, know you know how to make oxides.
What about even oxidation numbers? You just have to simplify it if you can.

OXIDE/ANHYDRIDE NOMENCLATURE

Now that we know how to make the formulas of oxides, we have to know how to name then correctly.

There are 3 ways of naming oxides.

  • TRADITIONAL nomenclature
  • IUPAC nomenclature
  • STOCK nomenclature

TRADITIONAL NOMENCLATURE
To name oxides according to the traditional nomenclature you need to learn a little system of prefixes and suffixes (for the oxidation numbers)

  • If it only has 1 oxidation number there isn’t a suffix to use, some people use the –ic suffix.
  • If it has 2
-ous
-ic
+2
+3
+1
+2
Note that the suffix does not depend on the number but on how many valences the element has. I’ve seen people making the mistake to think that +2 is always –ous or always –ic.

EXAMPLE

Name this oxide

Mn2O3

Remember how to make oxide formulas? Now we just need to go backwards to figure out which oxidation number the metal is using.
 Now that we know which it is, let’s find the correct suffix to use. It has 2 oxidation numbers:

+2 ----> -ous

+3 ----> -ic

Traditional nomenclature has this writing structure:

[ELEMENT NAME][SUFFIX] Oxide

So we just need to fill the name of the metal and the suffix

Manganic Oxide

Be careful with some element names, some aren’t use in nomenclature, such as IRON (Fe): so it wouldn’t be IRONIC OXIDE (heheh), but FERRIC OXIDE

IUPAC NOMENCLATURE

This one is the easiest in my opinion, it is also called “systematic”; you just need to learn these prefixes:

Number
Prefix
1
mono-
2
di-
3
tri-
4
tetra-
5
penta-
6
hexa-
7
hepta-
8
octa-
9
nona-
10
deca-
EXAMPLE:

Mn2O3

You just need to use the prefixes to name the element according of the subscripts.
In this case the structure of IUPAC nomenclature is

[PREFIX][ELEMENT NAME]  [PREFIX]Oxide

So this is the name of the oxide according to IUPAC Nomenclature:

diManganese triOxide

STOCK NOMENCLATURE

This is an easy nomenclature as well; you don’t have to know anything else but the oxidation numbers of the elements.

EXAMPLE:

Mn2O3

First step is to figure out the oxidation number of the metal:
 The structure of STOCK nomenclature is

[ELEMENT NAME][OX. NUMBER]     Oxide

The oxidation number of the metal has to be written in Roman numbers (I, II, III, IV, etc.).
This is the name according to Stock Nomenclature:

Manganese(III) Oxide

Be careful with writing a space between the name and the Roman number, there isn't one.

Coming Up!: Oxide Exercises


 
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