Presentation on theme: "Chaos. Thats something we are all familiar with.."— Presentation transcript:
Chaos. Thats something we are all familiar with.
Theres even a movie called chaos. Life is full of it and we all try to reduce it. We want to feel organized. Few of us want the world to be chaotic.
Chaos goes beyond our lives and our world. This writer addresses chaos throughout the universe and its stunning complexity. Throughout human history, we have tried to make more sense out of the world around us. To reduce the chaos, we tried to perceive a more simpler underlying fabric of the world. Chaos goes beyond our lives and our world. This writer addresses chaos throughout the universe and its stunning complexity. Throughout human history, we have tried to make more sense out of the world around us. To reduce the chaos, we tried to perceive a more simpler underlying fabric of the world.
Thales (600 B.C.) Water In 600 B.C. the Greek philosopher Thales proposed that everything in the world was made from water. Water was the only element. All living things consume water and perhaps water is creating all the matter living things are composed of.
Xenophanes (500 B.C.) EarthWater In 500 B.C. the Greek philosopher Xenophanes felt water couldnt be the element for everything. It seemed the world was made two elements, earth and water.
Empedocles (440 B.C.) Four elements Earth Water Air Fire (more commonly called dirt) 60 years later Empedocles felt the universe required four elements. Earth, water, fire, and air.
As leaves change their color, you can see the fire that they contain. Anything that burns will reveal that it is made of the four elements (At this point, I crumpled some paper and lit a match to it.) Notice there is fire in this paper. Also, I feel wind rising from it. As I hold this cold beaker above it, you can see water condensing on it. So the dry paper actually has water in it. Finally as it burns out you see the ashes, which is like dirt or earth. As leaves change their color, you can see the fire that they contain. Anything that burns will reveal that it is made of the four elements (At this point, I crumpled some paper and lit a match to it.) Notice there is fire in this paper. Also, I feel wind rising from it. As I hold this cold beaker above it, you can see water condensing on it. So the dry paper actually has water in it. Finally as it burns out you see the ashes, which is like dirt or earth.
Democritus Athens, Greece 400 B.C. 40 years later, Democritus said, Ok there may be four elements, but I believe these elements are not as they appear.
The mountains look solid and the water seems smooth, but that because theres a limit to our vision.
For example, from a distance, we cannot see the individual grains of sand that this beach is made from.
However, up close we know there are individual grains.
I think elements are like this. They are made of individual particles, that in huge numbers become visible and know to us.
Since atomos is the Greek word for indivisible I shall call these particles atoms. Atoms cannot be destroyed, so there is conservation of matter. The smallest particles of matter are indivisible. I also believe that these small particles are indivisible. In other words, there is a limit to how small matter can be broken. Since atomos is the Greek word for indivisible I shall call these particles atoms. Atoms cannot be destroyed, so there is conservation of matter. We may see water evaporate or wood burn, but the matter or atoms are still around.
Aristotle Athens, Greece 340 B.C. Aristotle also had opinions on chemistry. However, Aristotle had the most influence on the history of chemistry. Besides chemistry, he also tackled physics, biology, psychology, and logic. About 60 years later, Aristotle also had opinions on chemistry. However, he had the most influence on the history of chemistry.
Its ironic that the theories of Aristotle which were most accepted were also the most incorrect. For example, he proposed and embraced the mystical fifth element. It took chemists 2,000 years to recognize that there was no mystical fifth element.
Democritus said atoms cannot be divided. You cannot place restraints on the gods. Therefore, matter cannot be made up of indivisible particles. Atoms cannot exist. Democritus Aristotle disagreed with Democritus
The concept of the atom fell out of favor for 2,000 years until… Democritus view of what atoms might look like.
John Dalton England 1796 John Dalton began teaching when he was 12. Dalton was a humble man with several apparent handicaps: he was poor; he was not articulate; he was not a skilled experimentalist; and he was color-blind. Dalton is best known for his atomic theory, which revolutionized the science of chemistry and brought back Democritus concept of the atom.
Elements are composed of minute, indivisible particles called atoms
All atoms of that element are alike. Plus those atoms are not like the atoms of any other element. Gold Copper
Chemical compounds are formed by the union of two or more atoms of different elements.
Atoms combine to form compounds in simple ratios, such as 1:1, 1:2, 2:2, 1:3, and so forth. Law of Definite Proportions
Atoms of two elements may combine in different ratios to form more than one compound. We call this: The Law of Multiple Proportions
Reactions are just a rearrangement of atoms. Oxygen and hydrogen gas reacting to form water
Ba(OH) 2. 8H 2 O(s ) + 2 NH 4 SCN(s ) --> Ba(SCN) 2 (s ) + 10 H 2 O(l ) + 2 NH 3 (g ) Ca O O O O S Ba O H O H Reactions are just a rearrangement of atoms.
Daltons Elements Arranged from light to heavy by their relative weights Through experiments, Dalton was getting rough estimates on the relative weights of known elements. The second is Azote, A for no and Zote for life. The gas was nitrogen, and living things die if only breathing nitrogen. Some were not elements. Lime is actually calcium and oxygen combined, but Dalton didnt know that.
Johan Jacob Berzelius from Sweden This is the Swedish chemist, Johan Berzelius. Like Dalton, he was finding the relative weights of the elements. Berzelius in credited for the naming convention we use for elements.
Older elements take the symbol from their Latin name. Fe comes from ferrum not iron. Instead of G for gold he wants Au from aurum. Instead of S for Silver he wants Ag from argentum. Newer symbols come from English names. O comes from oxygen. 2000 experiments over a ten-year period to determine accurate relative atomic weights for all the elements now known. Berzelius Symbols for Elements
John Newlands England 1867 Researchers had already began to arrange and classify elements: Metals vs. non-metals In tables of increasing atomic weight John Newlands from England had a different way to arrange elements.
Chlorine, bromine & iodine violently corrosive form acids Lithium, sodium, potassium Unite violently with oxygen or water Oxides form caustic aqueous solutions Every eighth element have similar characteristics Li Be B C N O F Na Mg Al Si P S Cl K Ca ? ? As Se Br Certain elements resembled one another in behavior. I call this the Law of Octaves
Li Be B C N O F Na Mg Al Si P S Cl K Ca ? ? As Se Br I call this the Law of Octaves because of its similarity to musical octaves Lightest to heaviest. Li Be B C N O F Na Mg Al Si P S Cl K Ca ? ? As Se Br ABCDEFGABCDEFGABCDEFGABCDEFGABCDEFGABCDEFG
Law of Octaves He presented his theory to the England Chemical Society and was laughed at. They said to arrange it alphabetically.
Dmitri Ivanovich Mendeleev Russia 1871 Periodic Law Like Newlands, he used lithium, sodium, and potassium plus the chlorine family as guide posts Here is someone you dont laugh at.
Orginally Mendeleev arranged the elements with common properties in rows instead of columns. But here are the two groups of elements that acted as guide posts.
Gallium Germanium His table helped others find the missing elements.
As a tribute to Mendeleev, here is his Periodic Table of the Elements carved in stone.
In an effort to understand the chaos around us, we found order. The complexity of the universe is tamed by this table. It represents a comforting reminder that chaos is not in control. In an effort to understand the chaos around us, we found order. The complexity of the universe is tamed by this table. It represents a comforting reminder that chaos is not in control.
Learning Check Name an element that has similar properties to chlorine (Cl). Name an element that has similar properties to sodium (Na). Name an element that has similar properties to copper (Cu).
For example Helium shows the atomic mass of 4.00 and Oxygen is 16.00. That means that one atom of oxygen is 4 times heavier than helium. Oxygen has 4 times more protons and 4 times more neutrons (not shown in table) that account for this.
Learning Check How many times heavier is a calcium atom compared to a neon atom? How many times heavier is a calcium atom compared to a helium atom? How many times heavier is oxygen compared to carbon?
To understand it further we need to look closer at the makeup of the atom.
Its all about building blocks
Evolution of the atom Neutrons Electrons (-) Protons (+)
How do electrons think? + + +
Electrons dislike other electrons
Electrons love protons Electrons are strongly attracted to protons. The more protons present the stronger the attraction. +
Likes Repel Opposites Attract ++
` What do electrons do when both protons and electrons are present? + + They get as close to the protons as possible while maintaining as much distance as possible from other electrons. + + +
What would the right electron do? +
What would electrons in two hydrogen atoms do? + - + - + - - + Remember this is a simplistic version of the electron.
Building elements Hydrogen-1 Helium-2 Lithium-3 Carbon-6 Boron-5 Beryllium-4
Electrons are not the simple little particles that we often draw them. They demonstrate the dual nature of matter, which is both particle and wave. There shape or location is quite flexible. In this shape there are two lobes. The electron occupies both. Somehow is gets back and forth without passing through the middle space. Or it is in both locations at the same time. Either way it is not a simple particle. Also, its location is not fixed. The probability that it is in this region being drawn is high, but there is a probability that it can be farther away, even as far as the moon. An extremely small chance, I agree, but it is possible. So at this moment some of your electrons could be about anywhere. So you cant really say you never go anywhere. But the main thing to remember is not to underestimate the flexibility of electrons and their amazing abilities. Electrons give atoms their diversity.
Atomic Number Atomic number = number of protons in an atom 1 H 1.008 29 Cu 63.55 Hydrogen has one proton. Copper has 29 protons. Atomic Number
Learning Check What is the atomic number of cobalt (Co)? What is the atomic number of carbon (C)? How many protons does uranium (U) have?
Isotopes Mass number = the total number of protons and neutrons in an atom Isotopes have the same number of protons, but different numbers of neutrons. 12 C 6 14 C 6Atomic Number Mass Number 6 + 6 6 + 8 Carbon-12 & Carbon-14
Learning Check Naturally occurring carbon consists of three isotopes, 12 C, 13 C, and 14 C. State the number of protons, neutrons, and electrons in each of these carbon atoms. C C C # p _______ _______ _______ # n _______ _______ _______ # e _______ _______ _______ 6 6 6 6 7 8 6 6 6 12 13 14
Practice Problems How many protons are in the isotope? 35 protons What is the mass number of the isotope? The mass number is 80. How many neutrons are in the isotope? 80 (protons + neutrons) - 35 (protons) = 45 neutrons 80 Br 35 Answer the questions about the bromine-80 isotope.
Atomic Mass Atomic Mass = weighted average of the mass numbers of the isotopes of an element 12 C 12.01 Carbon has three isotopes C-12, C-13, C-14 with mass numbers of 12, 13, & 14 respectively. Most carbon atoms have 6 neutrons, so they have a mass number of 12. That is why the average of 12.01 is so close to 12. Atomic Mass If most carbon atoms had 8 neutrons, then the atomic mass would be closer to 14. Atomic #
Atomic Mass Atomic Mass = weighted average of the mass numbers of the isotopes of an element 1 H 1.008 29 Cu 63.55 Hydrogen has three isotopes: H-1, H-2 and H-3 Copper has two common isotopes: Cu-63 and Cu-65 Atomic Mass Which isotope is the most plentiful? Atomic #
Learning Check An atom of zinc has a mass number of 65. A.Number of protons in the zinc atom 1) 302) 353) 65 B.Number of neutrons in the zinc atom 1) 302) 35.393) 35 C. What is the mass number of a zinc isotope with 37 neutrons? 1) 372) 653) 67 30 Zn 65.39 Zn 30 65
Solution An atom of zinc has a mass number of 65. A.Number of protons in the zinc atom 1) 30 B.Number of neutrons in the zinc atom 2) 35 C. What is the mass number of a zinc isotope with 37 neutrons? 3) 67 Zn 30 67
The number of outer electrons (valence electrons) is shown by the group number
Valence Electrons These outer electrons are called valence electrons. (valens is Latin meaning to be strong. The word valiant also comes from valens). Valence electrons give the elements the strength to react with other elements. Valence electrons are given away, pulled in, or shared. This results in two elements combining or joining with each other. O
How do you recognize a metal?
This shows two defects on a surface of copper. The electrons form a lake on the surface of the copper. There are even waves. This probably accounts for the shiny property of metals and its conductivity.
Conducts electricity and are malleable This is as far as I got.
Non-metals Attract electrons (electronegative) Hold tightly to electrons More brittle Lighter More apt to be gas even when combined with other non-metals. Form salts when combined with metals One or more non-metals bonded to one or more metals. Usually water soluble.
Lithium-Li, Sodium-Na, Potassium-K, Rubidium-Rb, Cesium-Cs Rock Soda Pot Ashes Red Sky blue See page 79 in textbook for more origins of element names.
Sodium hydroxide and potassium hydroxide found in the ashes of the plant. H2OH2O The ashes of the plant were found to neutralize acids. Anything that can neutralize acids is now called alkaline
The alkali metals differ from other metals in several ways. They are soft, with low melting and boiling temperatures. They have low densities - Li, Na and K are less dense than water. When these elements are placed in a flame the heat pushes the outermost electron to a higher energy level. On returning to ground level, energy is emitted and this energy has a wavelength in the visible region: Li red Na yellow K lilac Rb red Cs blue
Beryllium, Magnesium, Calcium, Strontium, Barium, Radium These metals, when added to water, will produce solutions that are alkaline.
Alkaline Earth Metals These elements are all found in the Earths crust, but not in the elemental form as they are so reactive. Instead, they are widely distributed in rock structures. Calcium is found in chalk, limestone, and gypsum. Magnesium is the eighth most abundant element in the Earths crust, and calcium is the fifth. The metals of Group 2 are harder and denser than sodium and potassium, and have higher melting points. Three of these elements give characteristic colors when heated in a flame: Mg brilliant white Ca brick-red Sr crimson Ba apple green
Fluorine-F, Chlorine-Cl, Bromine-Br, Iodine-I, Astatine-At The total amount of astatine present in the Earth's crust is less than 1 oz Metals in contact with halogens will soon become a salt.
The halogens are the greediest of all the elements. They pull electrons off of other elements. Fluorine is the strongest. If they cant pull the electron completely off they will at least attract and keep it part of the time (electron sharing).
H 2 O + F 2 HF + O 2
The elements are also grouped into four blocks with different colors. These represent the different kinds of electron orbitals (also called shapes or clouds).