CHEMISTRY

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The periodic table of the chemical elements (also periodic table of the elements or just the periodic table) is a tabular display of the chemical elements. Although precursors to this table exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869, who intended the table to illustrate recurring ("periodic") trends in the properties of the elements. The layout of the table has been refined and extended over time, as new elements have been discovered, and new theoretical models have been developed to explain chemical behavior.^[1]
The periodic table is now ubiquitous within the academic discipline of chemistry, providing a useful framework to classify, systematize, and compare all of the many different forms of chemical behavior. The table has found many applications in chemistry, physics, biology, and engineering, especially chemical engineering. The current standard table contains 118 elements to date. (elements 1–118).

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Structure

Group #	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18
Period
1	1 H																	2 He
2	3 Li	4 Be											5 B	6 C	7 N	8 O	9 F	10 Ne
3	11 Na	12 Mg											13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
4	19 K	20 Ca	21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
5	37 Rb	38 Sr	39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
6	55 Cs	56 Ba	*	72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
7	87 Fr	88 Ra	**	104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Uut	114 Uuq	115 Uup	116 Uuh	117 Uus	118 Uuo

* Lanthanoids			57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb	71 Lu
** Actinoids			89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No	103 Lr

This common arrangement of the periodic table separates the lanthanoids and actinoids (the f-block) from other elements. The wide periodic table incorporates the f-block. The extended periodic table adds the 8th and 9th periods, incorporating the f-block and adding the theoretical g-block.

Element categories in the periodic table

Metals						Metalloids	Nonmetals			Unknown chemical properties
Alkali metals	Alkaline earth metals	Inner transition elements		Transition elements	Other metals		Other nonmetals	Halogens	Noble gases
		Lanthanides	Actinides

**Atomic number colors show state at standard temperature and pressure (0 °C and 1 atm)**
Solids	Liquids	Gases	Unknown

**Borders show natural occurrence**
Primordial	From decay	Synthetic	(Undiscovered)

Classification

Groups

Main article: Group (periodic table)

A group or family is a vertical column in the periodic table. Groups are considered the most important method of classifying the elements. In some groups, the elements have very similar properties and exhibit a clear trend in properties down the group. These groups tend to be given trivial (unsystematic) names, e.g., the alkali metals, alkaline earth metals, halogens, pnictogens, chalcogens, and noble gases. Some other groups in the periodic table display fewer similarities and/or vertical trends (for example Group 14), and these have no trivial names and are referred to simply by their group numbers.

Periods

Main article: Period (periodic table)

A period is a horizontal row in the periodic table. Although groups are the most common way of classifying elements, there are some regions of the periodic table where the horizontal trends and similarities in properties are more significant than vertical group trends. This can be true in the d-block (or "transition metals"), and especially for the f-block, where the lanthanides and actinides form two substantial horizontal series of elements.

Blocks

This diagram shows the periodic table blocks.

Main article: Periodic table block

Because of the importance of the outermost shell, the different regions of the periodic table are sometimes referred to as periodic table blocks, named according to the subshell in which the "last" electron resides. The s-block comprises the first two groups (alkali metals and alkaline earth metals) as well as hydrogen and helium. The p-block comprises the last six groups (groups 13 through 18) and contains, among others, all of the semimetals. The d-block comprises groups 3 through 12 and contains all of the transition metals. The f-block, usually offset below the rest of the periodic table, comprises the rare earth metals.

Other

The chemical elements are also grouped together in other ways. Some of these groupings are often illustrated on the periodic table, such as transition metals, poor metals, and metalloids. Other informal groupings exist, such as the platinum group and the noble metals.

Periodicity of chemical properties

The main value of the periodic table is the ability to predict the chemical properties of an element based on its location on the table. It should be noted that the properties vary differently when moving vertically along the columns of the table than when moving horizontally along the rows.

Trends of groups

Modern quantum mechanical theories of atomic structure explain group trends by proposing that elements within the same group have the same electron configurations in their valence shell, which is the most important factor in accounting for their similar properties. Elements in the same group also show patterns in their atomic radius, ionization energy, and electronegativity. From top to bottom in a group, the atomic radii of the elements increase. Since there are more filled energy levels, valence electrons are found farther from the nucleus. From the top, each successive element has a lower ionization energy because it is easier to remove an electron since the atoms are less tightly bound. Similarly, a group will also see a top to bottom decrease in electronegativity due to an increasing distance between valence electrons and the nucleus.

Trends of periods

Periodic trend for ionization energy. Each period begins at a minimum for the alkali metals, and ends at a maximum for the noble gases.

Elements in the same period show trends in atomic radius, ionization energy, electron affinity, and electronegativity. Moving left to right across a period, atomic radius usually decreases. This occurs because each successive element has an added proton and electron which causes the electron to be drawn closer to the nucleus. This decrease in atomic radius also causes the ionization energy to increase when moving from left to right across a period. The more tightly bound an element is, the more energy is required to remove an electron. Similarly, electronegativity will increase in the same manner as ionization energy because of the amount of pull that is exerted on the electrons by the nucleus. Electron affinity also shows a slight trend across a period. Metals (left side of a period) generally have a lower electron affinity than nonmetals (right side of a period) with the exception of the noble gases.

History

Main article: History of the periodic table

In 1789, Antoine Lavoisier published a list of 33 chemical elements. Although Lavoisier grouped the elements into gases, metals, non-metals, and earths, chemists spent the following century searching for a more precise classification scheme. In 1829, Johann Wolfgang Döbereiner observed that many of the elements could be grouped into triads (groups of three) based on their chemical properties. Lithium, sodium, and potassium, for example, were grouped together as being soft, reactive metals. Döbereiner also observed that, when arranged by atomic weight, the second member of each triad was roughly the average of the first and the third.^[4] This became known as the Law of triads.^{[citation needed]} German chemist Leopold Gmelin worked with this system, and by 1843 he had identified ten triads, three groups of four, and one group of five. Jean Baptiste Dumas published work in 1857 describing relationships between various groups of metals. Although various chemists were able to identify relationships between small groups of elements, they had yet to build one scheme that encompassed them all.^[4]
German chemist August Kekulé had observed in 1858 that carbon has a tendency to bond with other elements in a ratio of one to four. Methane, for example, has one carbon atom and four hydrogen atoms. This concept eventually became known as valency. In 1864, fellow German chemist Julius Lothar Meyer published a table of the 49 known elements arranged by valency. The table revealed that elements with similar properties often shared the same valency.^[5]
English chemist John Newlands published a series of papers in 1864 and 1865 that described his attempt at classifying the elements: When listed in order of increasing atomic weight, similar physical and chemical properties recurred at intervals of eight, which he likened to the octaves of music.^[6]^[7] This law of octaves, however, was ridiculed by his contemporaries.^[8]

Portrait of Dmitri Mendeleev

Russian chemistry professor Dmitri Ivanovich Mendeleev and Julius Lothar Meyer independently published their periodic tables in 1869 and 1870, respectively. They both constructed their tables in a similar manner: by listing the elements in a row or column in order of atomic weight and starting a new row or column when the characteristics of the elements began to repeat.^[9] The success of Mendeleev's table came from two decisions he made: The first was to leave gaps in the table when it seemed that the corresponding element had not yet been discovered.^[10] Mendeleev was not the first chemist to do so, but he went a step further by using the trends in his periodic table to predict the properties of those missing elements, such as gallium and germanium.^[11] The second decision was to occasionally ignore the order suggested by the atomic weights and switch adjacent elements, such as cobalt and nickel, to better classify them into chemical families. With the development of theories of atomic structure, it became apparent that Mendeleev had inadvertently listed the elements in order of increasing atomic number.^[12]
With the development of modern quantum mechanical theories of electron configurations within atoms, it became apparent that each row (or period) in the table corresponded to the filling of a quantum shell of electrons. In Mendeleev's original table, each period was the same length. However, because larger atoms have more electron sub-shells, modern tables have progressively longer periods further down the table.^[13]
In the years that followed after Mendeleev published his periodic table, the gaps he left were filled as chemists discovered more chemical elements. The last naturally occurring element to be discovered was francium (referred to by Mendeleev as eka-caesium) in 1939.^[14] The periodic table has also grown with the addition of synthetic and transuranic elements. The first transuranic element to be discovered was neptunium, which was formed by bombarding uranium with neutrons in a cyclotron in 1939.^[15]

Periodic Table of Elements

http://periodic.lanl.gov/default.htm

Saturday, November 27, 2010

TMBG Meet the Elements

They Might Be Giants: "Meet the Elements" (BB Video)

nababaliw na ako

sakit sa ulo...
tuyot na utak ko..
ooopppss my utak pala ako

www.youtube.com/watch?v=d0zION8xjbM

Activity Pack in Chem I

quiztime

The Periodic Table
http://www.youtube.com/watch?v=d0zION8xjbM
http://www.youtube.com/watch?v=zGM-wSKFBpo
http://www.youtube.com/watch?v=3NNcSOSna-k&feature=related

Overview

The periodic table was designed as a way to arrange all known elements so that

their properties and reactivities are easier to understand. Elements in the same

column are said to be in the same “group” or “family” and have similar chemical

and physical properties. Elements in the same row are said to be in the same

“period” and share an energy level. In this chapter, students will learn about the

arrangement of elements in the periodic table, and explore the extreme

difficulties experienced by the makers of the first periodic table.

Teaching about the Periodic Table

There is good news and bad news when it comes to teaching the periodic table.

The good news is that there’s nothing inherently difficult about learning the

periodic table – students really only need to learn the locations and properties of

the most important families. Frequently, this is taught as a coloring exercise –

“Color the transition metals orange, the halogens blue,” etc.

The bad news is that students find the periodic table to be very, very boring.

After all, who wants to color a periodic table in class when there are more

interesting things to be done?

How can we teach the periodic table in an exciting way? The bottom line is that

one way or another, our students will just have to memorize the table in the

traditional ways. However, by giving them equal quantities of memorization and

activity, the memorization will be a little easier to take.

Doing the Periodic Table Lab

Equipment:
The equipment for this lab consists of five bags containing identical collections of
small and easily obtained items from around the lab. These items should be
inexpensive things like paper clips, flints, vials, pens, pencils, nails, thumbtacks,
etc. When choosing these items, don’t pick a collection of items that will naturally
fall into easy categories – this lab works much better if the items are dissimilar in
many ways. Along with the familiar items above, include some items your
student probably haven’t seen before, such as cork borers, solder, parafilm
squares, etc.

Safety:
The items chosen for this lab shouldn’t be dangerous or toxic (no road flares,
blasting caps, sodium hydroxide pellets, and so on). As long as the items are
harmless, safety is not an issue with this lab.
Room destruction factor:
This lab is only as messy as the items you place in the bags. By using items that
are difficult to break, there should be no clean-up to speak of.
How the lab works:
In this lab, your students will treat each item as an “element” and attempt to
arrange them into a “periodic table” based on their properties. This is harder
than it might imagine, and takes a good deal of time.
Students typically have no difficulty separating the elements into groups. Popular
ways of arranging the elements include by composition (wood, metal, plastic,
etc.), by shape (round, pointed, etc.), and by colo r. The problem with this lab is
that it’s difficult to group the elements by period. After all, it’s not enough that the
elements are arranged by increasing size or mass – the elements have to be
arranged in a way that elements next to each other have roughly the same size
or mass, just as elements in the same period have roughly the same electron
energies. This becomes difficult if two elements in the same group have identical
masses, as only one element from each group can exist in each period.
As a result, simple groupings can’t be used for the elements in this lab. Your
students will show great inventiveness and creativity in their efforts to solve this
problem, making the lab both interesting to do and to watch.
After the lab ends, you may want to have each group present their periodic tables
to the whole class. Students will frequently be surprised at how other groups
have arranged their elements, and will undoubtedly have a new appreciation for
the difficulty involved in making the first periodic table.
What can go wrong:
· Sometimes students will never come to consensus within their groups.
There’s no much you can do to resolve these arguments, except to remind
each group that this lab is graded, necessitating some answer.
· The “elements” get lost or broken. It’s a good idea to have at least two
spares of each item to keep the lab moving smoothly.
· Students sometimes play with the items instead of classifying them. To avoid
this, don’t put Silly Putty or Slinky coils in the bags!
58
Solutions for the Periodic Table Lab
Prelab:
Although fluorine and iodine may be dissimilar, they have some important
characteristics in common. For example, both are good oxidizers, are
diatomic, and prefer a -1 oxidation state. Though these elements have
significant differences, the similiarities still outweigh the differences.
Lab:
The “elements” should be placed into groups by property. Make sure you
count the items on this page – students have developed the clever trick of
leaving out items that don’t fit into any clear category. Typcially, students
place less massive items at the top of each group and heavier ones at the
bottom, though different ways of denoting energy level may be favored by
different groups. The final product should look (roughly) like a periodic
table, though there may be more gaps than the one used to classify real
elements.
Postlab questions:
1) One property should have been chosen to classify their items, and there
should be some reasonable explanation for why this particular property
was used.
2) There should be some continuum from the top to bottom of each column.
For example, if they believe that three elements fit into a category, there
should be a property that varies slightly as you move down the column.
Common properties include mass, size, and density. Elements placed

3) Students should discuss the differences in how their arrangement differs
from those of a neighboring group. Any differences are most likely caused
by an emphasis on different properties – their answer should reflect this.
4) Students should explain how their differences were resolved. Sometimes
groups agree all the way down the line in how elements should be
arranged, but more frequently they vote or decide through painful trial and
error.
5) Clearly, emphasis on different properties made it difficult to devise the first
periodic table.
Solutions for the Periodic Table Worksheet
1) alkali metals
2) transition metals
3) noble gases
4) actinides

5) Alkaline earth metals are frequently soft, low-density, reactive, and
metallic elements that prefer to form ions with a +2 oxidation state.
6) Halogens are extremely reactive diatomic elements that prefer to form
ions with a -1 oxidation state. Halogens may be gases (F2, Cl2), liquids
(Br2), or solids (I2). All are volatile under normal conditions. They are
difficult to handle and are strong oxidizers.
7) Elements in the same family have similar properties.
8) Elements in the same period have similar orbital energies.
Solutions to the “Make your own periodic table” worksheet
The elements shown correspond to the alkaline earth metals (group 2), group 11,
the halogens (group 17), and the noble gases (group 18). Specifically, the
identities of the elements should be arranged in the following way:
beryllium (1) copper (6) fluorine (2) neon (8)
calcium (3) silver (5) bromine (9) argon (10)
barium (7) gold (12) astatine (11) xenon (4)

Periodic Table Handout

The periodic table is what chemists have used for over a hundred
years to organize the known elements.
Periods correspond to horizontal rows in the periodic tble. Generally,
the elements within a period have little in common, except for the
energy levels of the electrons.
Families (also called “groups”) correspond to the vertical columns in
the periodic table. Elements within each family share similar
properties. These similarities occur because elements in the same
family have the same number of valence electrons. Important
families within the periodic table include:
· Alkali metals (group 1): Extremely reactive, soft metals with low
density that form ions with a +1 charge.
· Alkaline earth metals (group 2): Slighly less reactive than alkali
metals, they are somewhat denser and less soft. They form ions
with a +2 charge.
· Halogens (group 17): Highly reactive and electronegative
nonmetallic elements that form ions with a -1 charge. They are
diatomic, volatile, and very difficult to handle safely.
· Noble gases (group 18): Very stable nonmetallic gases that
react poorly with other elements.
Other important sections of the periodic table include:
· Transition metals (groups 3-12): Dense, hard metallic elements
that usually form ions with more than one possible positive charge.
· Lanthanides and actinides (the two rows at the bottom of the
periodic table): The lanthanides are the top row and are reactive,
dense metals. The actinides are the bottom row and include
mainly radioactive elements that are produced artificially. Uranium
is the most important actinide, used for nuclear power and
weapons applications.
· Main group elements: These elements consist of groups 1, 2,
and 13-18. They have very little in common except that they have
either s- or p- electrons as their outermost electrons.
61

Periodic Table Lab

As you’ve learned, the periodic table is arranged in periods and families (families
are also known as groups). Periods correspond to the horizontal rows – for
example, lithium, beryllium, boron, carbon, and nitrogen are in the same period.
Elements in the same period may have very little in common. For example,
lithium reacts readily with water, while nitrogen requires very high temperatures
to react with water.
The elements in each family of the periodic table have similar properties. For
example, all of the alkali metals (group 1) react readily with water. The reason
for this similarity in reactivity is that the electron configurations for every element
in a family are similar, containing the same number of valence electrons in the
same type of orbital.
We usually take the periodic table for granted, not thinking much about how it
was invented. It seems obvious to us now that elements should be grouped by
properties and electron configurations. However, back in the 1800’s there were
many alternative ways to arrange the elements because not all of them had been
discovered and nobody really understood atomic structure. The periodic table
we use today is the product of many years of revisions by the best scientists of
that time.
In this lab, we’re going to imagine we’re scientists presented with a variety of new
elements, and we’re going to arrange them in the most logical way, based on
their properties.

Prelab:

In the current periodic table, fluorine is shown in the same family as iodine.
However, fluorine is a pale yellow gas, while iodine is a violet, shiny solid. Was a
mistake made when these were placed in the same group? Explain.
62
Lab:
Your group will be given a bag containing 20 items. As scientists, it’s your job to
group these items into families and periods, based on their observable
properties. You may make as many families and periods as you like, but there
should be some order to how they are arranged. Use the rest of this sheet to
draw your periodic table, and make sure you use a ruler!

Postlab questions:
1) What was the main property you used to classify the elements into
groups? Explain why you chose this property and not another.
2) Explain how you decided which element should go at the top of each
column and which should go at the bottom.
3) Look at the way another lab group arranged their elements. Is it the same
as the way you arranged yours? Why or why not?
4) Did you have disagreements within your group about how these elements
should be arranged? If so, explain how these disagreements were
resolved.
5) Does this exercise give you any insight as to why it may have been
difficult to invent the first periodic table? Explain.

Periodic Table Worksheet
For questions 1-4, fill in the blanks with the correct word or phrase:
1) The ________________________ are reactive, light metals that form ions
with a charge of +1.
2) The ________________________ are dense, strong metals that have
high melting and boiling points.
3) ________________________ are unreactive, nonmetallic gases.
4) ________________________ are mainly radioactive, manmade elements.
Answer the following questions:
5) What are the properties of the alkaline earth metals?
6) What are the properties of the halogens?
7) What similarities to elements in the same family share?
8) What similarities to elements in the same period share?

Make your own Periodic Table Worksheet
You’ve heard how the periodic table was invented and had a chance to make
one in class. Now that you’re a pro at classifying elements, you get a chance to
make your very own periodic table using real elements. If you do this correctly,
your classification scheme should be the same as the actual periodic table.
Unfortunately, you’re not going to be given the names of the elements or a
complete list of their properties. Using partial information (such as scientists had
in the old days), see if you can arrange these real elements into their proper
periods and families. One hint: These elements should be arranged into a grid
that’s three boxes tall by four boxes wide, with no blank spaces.
In no particular order:
Element 1: Solid, metal, does not corrode in air, density = 1.85 g/mL.
Element 2: Yellow gas, highly dangerous to handle, toxic in low doses.
Element 3: White, shiny, metallic solid, reacts slightly in air, density = 1.55 g/mL.
Element 4: Colorless gas, stable in air, forms very few chemical compounds.
Element 5: White, shiny metallic solid, unreactive, good electrical conductor,
ductile, density = 10.5 g/mL.
Element 6: Orange-red metallic solid, ductile, density = 8.9 g/mL.
Element 7: White metallic solid, reacts easily in air, density = 3.5 g/mL.
Element 8: Colorless gas, unreactive with any element.
Element 9: Red nonmetallic liquid, irritates skin and lungs.
Element 10: Colorless gas, denser than air, forms no chemical compounds.
Element 11: Radioactive metalloid, very little known about its properties.
Element 12: Yellow metallic solid, extremely malleable, unreactive with most
chemicals, density = 19.3 g/mL.
Good luck!

Evaluation:
Part I: http://glencoe.mcgraw-hill.com/sites/0078807239/student_view0/chapter3/standardized_test_practice.html
Part II: http://glencoe.mcgraw-hill.com/sites/0078807239/student_view0/chapter3/chapter_test_practice.html