Posts Tagged ‘honduras border’

Science Makes Sense, Week 18: Periodic Table, order

December 28, 2015

Organize, categorize, use colored stickers to mark differences.  This is how we arrange and try to understand differing groups in any subject we study. Chemistry is no different.  As soon as the definition of elements was laid out, chemists set about discovering new elements and placing them together initially based on melting points, density, and boiling point data. Today with knowledge about atomic mass, atomic number and the internal structure of an atom we have  a clear, concise way of classification called the Periodic Table.

The History of the Periodic Table is a fascinating study by itself in the field of chemistry.  Although elements like gold, silver, copper, tin, mercury, lead (Au, Ag, Cu, Sn, Hg,Pb) were known since the alchemists, the first official discovery of an element, phosphorus, P, took place in 1649 ( Week 17).  The next 200 years, 63 elements were discovered and could be classified. (Ref. 1)

Law of triads:  Initially, bunches of 3 elements were found to have similar properties.  For example,  the atomic weight of strontium,  was found to be between calcium and barium and similarly flourine, chlorine and bromine were found to be similar in properties.  So there was a theory floating about bunches of 3 elements with similar properties.  With the discovery of more elements in these bunches, one could see that the law of triads was a limited idea. (Ref. 1)

Using a special kind of cylinder, it was seen that every 16 elements showed similar properties.  This was one of the first attempts in the classification of elements. (Ref. 1)

Chancourtoisin in 1862 was the first to recognize that elemental properties recur every seven elements, but it was Dimitri Mendeleev, the Russian chemist who is credited with the first credible periodic table of 63 elements.  What was so remarkable was the fact that he was able to predict properties of elements that were in the gaps long before they were discovered, based on their possible position in the table. (Ref. 1)

The discovery of sub-atomic particles, the discovery of atomic numbers for elements in the 20th century, paved the way to organize the Periodic Table as it is today.  (Ref. 1) The presence of a certain amount of order in the electronic arrangement in different shells led to the arrangement of elements in groups of two, eight and eighteen.  The pattern of arrangement of these elements give us invaluable information; no wonder the Periodic Table is considered the backbone of Chemistry!


Activities for Middle School Teachers:

Take a bunch of household items and categorize them like a periodic table. Justify your classifications!

During harvest season, let students bring pumpkins and carve the name of an element in each pumpkin to create a Periodic Table of pumpkins. Use other items, like leaves, pieces of different colored cloth, to do the same thing.

Do a research project on the different kinds of Periodic Tables created.

Nuggets of Information:

Each row of the Periodic Table is called a period and each column is called a Group.  For example, there are only two elements, Hydrogen,H and Helium, He, in the first period of the Periodic Table.  Elements in a group exhibit similar behavior: alkali metals, Lithium,Li, sodium, Na, potassium K, through Francium, Fr, (elements in blue) have similar properties. Again, the  Noble Gases in Group 8 ( Helium, He, Neon, Ne, Argon,Ar. etc) are inert and do not react with anything.  Elements in a Group have an identical outer shell electronic arrangement. (Ref.3)

Ninety elements in the Periodic Table occur in nature; the rest have been synthesized in the laboratory. (Ref.3)

Technitium was the first element to be made in the laboratory. (Ref.3)

The present Periodic Table has room for 118 elements. (Ref.3)






Click to access Periodic-Table-of-the-Elements-12pg.pdf

Click to access Periodic-Table-of-the-Elements-12pg.pdf

Click to access Periodic-Table-of-the-Elements-12pg.pdf

Guatemala diaries: Copan, Honduras

April 1, 2013

248258273280297The stolen wallet leaves a mark on both of us. We are  irritated to have to get up early and avoid each other in the morning. I sit at the very back and meet a delightful couple called Cara and Steve from Washington State. Cara is a weaver and jewellery maker and her partner Steve carves wood. They share their brochures and spend a lot of time chatting with me. They have all heard about our recent loss and are very concerned. Right in the frontof the bus are the Barcelona pair, Paco and Jaunita and behind them are the two older gentleman from Canada. With Arty and the driver we are 10 of us in the bus. Arty is very good  giving us vivid details about our next part of the journey and we actually go through different parts of Guatemala city before going northeast to the Honduras border.

I have to say a word about the weather; almost every day has been sunny and pleasant. Arty says we are now approaching the warmer regions and except for a boat ride on Rio Dulce,we will feel warm most of the time. I am looking forward to it, though I never complained about the cool weather in the southern part of the country.

Copan is across the border and you realize that the Mesoamerican culture of the Mayas must have extended from southern Mexico all the way through Honduras. Arty tells us that after lunch at Copan, we will have a new guide there and he will meet us later.

Lunch is a filet of fish with some cooked veggies and rice, fairly decent stuff and we wash it down with water.We can use our quetzales or convert to lempiras. We wait for the new guide and Paco and Juanita start chatting as we wait. My husband buys a hat for me since it is getting really warm and sunny. I cradle the water bottle in my hands and keep taking swigs as we chat.

Then we go with the guide. We are 8 of us excluding the thin tall guide who takes us to a wooden board to explain the ruins of Copan. I hear macaws around me and my husband tries to get a picture of one of them.

The guide has a long wooden stick with a feather at the end. He explains that they are supposed to be very careful when they point at the stone structures and not in anyway cause marks. The ruins of Copan talk about the mayan people  living there from 1200BC   and leaving almost 850 years after the birth of Christ. The ending of this civilization is considered a mystery, but it seems to point to the fact that the mayans moved because of too much strain to the natural resources in that area.

I am struck by the beautiful stone structures that are called Stela and marked with an alphabet.  On the sides is heiroglyphics that depict the time period.  Some are protected by a cottage-like roof on top.  I love their sports arena where they played something like basketball, but used their hips and elbows to move the ball. What dexterity they must have had!  And then I see trees growing among the stones and the guide tells us that archeologists will  not move the trees and cause the crumbling of the stone structures, like Pompeii reconstruction caused. I am reminded of the Angkor Wat complex where the trees grow out of the stone faces. There is a lot to see and we walk around looking at the excavations that are still going on.  I am impressed by one statue where the last king is holding the hand of the first king.  Our guide tells us that there is more to be discovered in Copan. Amazing place!

Arty comes back and takes us to our hotel for the night.Both of us go for a walk  around the hotel and find a lovely cafe for wonderful coffee, Cafe Welchez.  I am tempted to have a sandwich there for dinner but we want to explore the town. The cobblestoned streets and the friendly people make this a perfect border town.  Paco and Juanita join us for dinner at this place which reminds me so much of the NYU area in downtown Manhattan.  The food( Cafe Via Via) is excellent here- vegetable soup&’ muchachas’:  a tortilla sandwich with melted cheese in between. I chatter in spanish with Juanita leaving my husband and Paco staring and smiling politely at each other. We walk back to the Hotel Marina which has a beautiful garden area near the swimming pool and we meet a lot of vacationing Americans who are having a good time there.  I sit down to collect my thoughts and put it on paper, hoping to have good news in Puerto Barrios the next day regarding the money and new credit cards….