Presentation on theme: "The Periodic Table. Here it is. Memorize it. Why is the Periodic Table important to me? The periodic table is the most useful tool to a chemist. You."— Presentation transcript:
The Periodic Table
Here it is. Memorize it.
Why is the Periodic Table important to me? The periodic table is the most useful tool to a chemist. You get to use it on every test. It organizes lots of information about all the known elements.
Pre-Periodic Table Chemistry … …was a mess!!! No organization of elements. Imagine going to a grocery store with no organization!! Difficult to find information. Chemistry didnt make sense.
During the nineteenth century, chemists began to categorize the elements according to similarities in their physical and chemical properties. The end result of these studies was our modern periodic table.
For Each Dude, fill in the Date and the Designation! DobereinerNewlandsMendeleev MeyerMoseleySeaborg
Johann Dobereiner Model of triads In 1829, he classified some elements into groups of three, which he called triads. The elements in a triad had similar chemical properties and orderly physical properties. (ex. Cl, Br, I and Ca, Sr, Ba)
John Newlands Law of Octaves In 1863, he suggested that elements be arranged in octaves because he noticed (after arranging the elements in order of increasing atomic mass) that certain properties repeated every 8th element.
John Newlands Law of Octaves Newlands' claim to see a repeating pattern was met with savage ridicule on its announcement. His classification of the elements, he was told, was as arbitrary as putting them in alphabetical order and his paper was rejected for publication by the Chemical Society.
John Newlands Law of Octaves His law of octaves failed beyond the element calcium. WHY? Look at Be and Mg – they both are bordered on the right by the P BLOCK. How many electrons are s and p together?
Dmitri Mendeleev In 1869 he published a table of the elements organized by increasing atomic mass.
Lothar Meyer At the same time, he published his own table of the elements organized by increasing atomic mass.
Elements known at this time
Both Mendeleev and Meyer arranged the elements in order of increasing atomic mass. Both left vacant spaces where unknown elements should fit. So why is Mendeleev called the father of the modern periodic table and not Meyer, or both?
stated that if the atomic weight of an element caused it to be placed in the wrong group, then the weight must be wrong. (He corrected the atomic masses of Be, In, and U) was so confident in his table that he used it to predict the physical properties of three elements that were yet unknown. Mendeleev...
After the discovery of these unknown elements between 1874 and 1885, and the fact that Mendeleevs predictions for Sc, Ga, and Ge were amazingly close to the actual values, his table was generally accepted.
Mendeleevs Table Activity
What to Do? Follow the directions on the half sheet Work alone or with a partner Your table will have 7 columns and 6 rows You MUST fill in missing observations on 5 elements (front table) You MUST place the 9 unknowns and NAME EACH ONE! You MUST designate AT LEAST 3 different physical/chemical properties DESIGNATED WITH A COLOR CODE
However, in spite of Mendeleevs great achievement, problems arose when new elements were discovered and more accurate atomic weights determined. By looking at our modern periodic table, can you identify what problems might have caused chemists a headache? Ar and K Co and Ni Te and I Th and Pa
Henry Moseley In 1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements*. He rearranged the elements in order of increasing atomic number. *There is in the atom a fundamental quantity which increases by regular steps as we pass from each element to the next. This quantity can only be the charge on the central positive nucleus.
Henry Moseley His research was halted when the British government sent him to serve as a foot soldier in WWI. He was killed in the fighting in Gallipoli by a snipers bullet, at the age of 28. Because of this loss, the British government later restricted its scientists to noncombatant duties during WWII.
Glenn T. Seaborg After co-discovering 10 new elements, in 1944 he moved 14 elements out of the main body of the periodic table to their current location below the Lanthanide series. These became known as the Actinide series
Glenn T. Seaborg He is the only person to have an element named after him while still alive "This is the greatest honor ever bestowed upon me - even better, I think, than winning the Nobel Prize."
The Modern Periodic Table
6 San Francisco 7 4 San Diego 6 5 Alburquerque 7 5 New Orleans 8 7 Green Bay 7 5 New York 7 5 Buffalo 7 6 Pittsburgh 8 5 Houston 8 4 Oakland 7 2 Seattle 7 4 Tampa Bay 7 6 Detroit 8 3 Dallas 7 5 New England 7 5 Cincinnati 7 4 Tennessee 7 3 Kansas City 6 1 Arizona 7 4 Atlanta 7 4 Chicago 7 3 Washington 7 4 New York 7 5 Baltimore 7 2 Jacksonville 8 2 Denver 5 1 St Louis 7 2 Carolina 8 2 Minnesota 8 3 Philadelphia 7 0 Miami 7 3 Cleveland 7 0 Indianapolis 8 0 Santa Barbara 8
Atomic Symbols Different Periodic Tables give different information. All of them give Atomic Symbol (X). Usually they give the Atomic Number (Z). Some give more. Some give more. But even without all the fancy info, just knowing where you are on the table gives real, solid info! Lets find out how!
Periodic Table Geography
The horizontal rows of the periodic table are called PERIODS.
The vertical columns of the periodic table are called GROUPS The elements in any group of the periodic table have similar physical and chemical properties! Why?? They have the same number of valence electrons. They will form the same kinds of ions.
Valence Electrons What Do We Want? WHY? s 2 p 6
Jigsaw Activity This activity is meant to take you through the groups of the periodic table. You will be responsible to read ONE section of 4-2 and take notes. In your first group, you will COMPARE NOTES and make sure you read it right.
Jigsaw Activity Once you have your notes, we will switch groups, and you will get the notes on the other sections from other people who read. WE WILL HAVE A QUIZ AT THE BEGINNING OF THE PERIOD TOMORROW ON THIS SO GET MOVING!
Jigsaw Notes – what you need With the exception of Hydrogen, pg 128 – Only need properties. Get on your own
Periodic Law When elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical and chemical properties.
Families on the Periodic Table Columns are also grouped into families. Families may be one column, or several columns put together. Families have names rather than numbers. (Just like your family has a common last name.)
Characteristic Areas of the PT
Hydrogen Hydrogen belongs to a family of its own. Hydrogen is a diatomic, reactive gas. Hydrogen was involved in the explosion of the Hindenberg. Hydrogen is promising as an alternative fuel source for automobiles
Metals Metals are lustrous (shiny), malleable, ductile, and are good conductors of heat and electricity. They are mostly solids at room temp. What is one exception?
METALS ARE SHADED YELLOW
Alkali Metals Group 1
Alkaline Earth Metals Group 2
Transition Metals Groups 3-12
Baby Youre A Rich Man Why would rich folk take to using SILVER to make PLATES and UTENSILS? Or Copper in their money? It has been found that these metals have an ANTIBIOTIC quality; germs cant stay alive on these metals. Take note – what are door handles and stair rails usually made of? Why?
InnerTransition Metals These elements are also called the rare-earth elements. Theyre called: Lanthanide series Actinide Series
Metals vs Nonmetals
Nonmetals Nonmetals are the opposite. They are dull, brittle, nonconductors (insulators). Some are solid, but many are gases, and Bromine is a liquid.
Metalloids Metalloids, aka semi-metals are just that. They have characteristics of both metals and nonmetals. They are shiny but brittle. And they are semiconductors. What is our most important semiconductor?
METALLOIDS ARE SHADED GREEN NON-METALS ARE SHADED BLUE
Boron Family (triels) Group 13
Carbon Family (tetrels) Group 14
Phicogens a.k.a. pnictogens Group 15
Chalcogens Group 16
Halogens Group 17
Noble Gases Group 18
The s and p block elements are called REPRESENTATIVE ELEMENTS or the MAIN GROUP.block
Periodic Table: The three broad Classes Main, Transition, Rare Earth Main (Representative), Transition metals, lanthanides and actinides (rare earth)
Code Your Periodic Table! Ive given you a Periodic Table With your NOTES ONLY (no text book, no friends, no friends notes) you must COLOR CODE YOUR PERIODIC TABLE This will count as a QUIZ GRADE You MUST have a KEY and follow directions
Periodic Trends There are several important atomic characteristics that show predictable trends that you should know.
Valence Electrons Do you remember how to tell the number of valence electrons for elements in the s- and p-blocks? How many valence electrons will the atoms in the d-block (transition metals) and the f- block (inner transition metals) have?
Valence Electrons e - configuration comes from the periodic table B 2p 1 H 1s 1 Li 2s 1 Na 3s 1 K 4s 1 Rb 5s 1 Cs 6s 1 Fr 7s 1 Be 2s 2 Mg 3s 2 Ca 4s 2 Sr 5s 2 Ba 6s 2 Ra 7s 2 Sc 3d 1 Ti 3d 2 V 3d 3 Cr 4s 1 3d 5 Mn 3d 5 Fe 3d 6 Co 3d 7 Ni 3d 8 Zn 3d 10 Cu 4s 1 3d 10 B 2p 1 C 2p 2 N 2p 3 O 2p 4 F 2p 5 Ne 2p 6 He 1s 2 Al 3p 1 Ga 4p 1 In 5p 1 Tl 6p 1 Si 3p 2 Ge 4p 2 Sn 5p 2 Pb 6p 2 P 3p 3 As 4p 3 Sb 5p 3 Bi 6p 3 S 3p 4 Se 4p 4 Te 5p 4 Po 6p 4 Cl 3p 5 Be 4p 5 I 5p 5 At 6p 5 Ar 3p 6 Kr 4p 6 Xe 5p 6 Rn 6p 6 Y 4d 1 La 5d 1 Ac 6d 1 Cd 4d 10 Hg 5d 10 Ag 5s 1 4d 10 Au 6s 1 5d 10 Zr 4d 2 Hf 5d 2 Rf 6d 2 Nb 4d 3 Ta 5d 3 Db 6d 3 Mo 5s 1 4d 5 W 6s 1 5d 5 Sg 7s 1 6d 5 Tc 4d 5 Re 5d 5 Bh 6d 5 Ru 4d 6 Os 5d 6 Hs 6d 6 Rh 4d 7 Ir 5d 7 Mt 6d 7 Ni 4d 8 Ni 5d 8
How does this affect behavior? Metals on the LEFT will ditch their electrons… to get to: This makes them CHUMPS Nonmetals on the RIGHT will steal electrons… to get to: This makes them THIEVES
The Octet Rule The goal of most Main Group atoms (except H, Li and Be) is to have an octet or group of 8 electrons in their valence energy level. Recall: Atoms that have gained or lost electrons are called ions.
Ions Here is a simple way to remember which is the cation and which the anion: This is a cat-ion. This is Ann Ion. Hes a plussy cat! (metals) Shes unhappy and negative. (nonmetals) +
Tell me, CHUMP or THIEF
Atomic Radius The most important atomic trend is atomic radius. Think of a radius in a circle Radius is the distance from the center of the nucleus to the edge of the electron cloud.
Atomic Radius Since a clouds edge is difficult to define, scientists use define covalent radius, or half the distance between the nuclei of 2 bonded atoms. Atomic radii are usually measured in picometers (pm) or angstroms (Å). An angstrom is 1 x m. Distance between 2 atoms ½ distance= atomic radius
What do you think? Which would be bigger? H or Pb? Why? Which would be bigger, H or K? Why?
Atomic Radius The trend for atomic radius in a vertical column is to go from smaller at the top to larger at the bottom of the family. Why? With each step down the family, we add an entirely new PEL (photoelectron layer) to the electron cloud, making the atoms larger with each step.
Analogy I tend to call each LAYER of electrons, or each FLOOR the electron hotel has populated – a new COAT. Whos gonna be bigger around – someone who has one tiny jacket on, or someone who is 223 pounds with 7 coats?
Atomic Radius The trend across a horizontal period is less obvious. What happens to atomic structure as we step from left to right? Each step adds a proton and an electron (and 1 or 2 neutrons). Electrons are added to existing PELs or sublevels.
Effective Nuclear Charge What keeps electrons from simply flying off into space? Effective nuclear charge is the pull that an electron feels from the nucleus. The closer an electron is to the nucleus, the more pull it feels. As effective nuclear charge increases, the electron cloud is pulled in tighter.
Atomic Radius Going left to right increases the SIZE OF THE NUCLEUS WITHOUT ADDING ANY TO THE PELs! The nucleus is more positive and the electron cloud is more negative. The increased attraction pulls the cloud in, making atoms smaller as we move from left to right across a period.
Shielding As more PELs are added to atoms, the inner layers of electrons shield the outer electrons from the nucleus. The effective nuclear charge (enc) on those outer electrons is less, and so the outer electrons are less tightly held.
Trend in Atomic Radius Trend in Atomic Radius Atomic Radius: The size of at atomic specie as determine by the boundaries of the valence e-. Largest atomic species are those found in the SW corner since these atoms have the largest n, but the smallest Z eff.
Atomic Radius Here is an animation to explain the trend. On your help sheet, draw arrows like this:
Ionization Energy This is the second important periodic trend. If an electron is given enough energy (in the form of a photon) to overcome the effective nuclear charge holding the electron in the cloud, it can leave the atom completely. The atom has been ionized or charged. This is a slight misnomer – this is only making CATIONS, not anions
This gymnast has been ionized
Ionization Energy The energy required to remove an electron from an atom is ionization energy. (measured in kilojoules, kJ) The larger the atom is, the easier its electrons are to remove. Ionization energy and atomic radius are inversely proportional. Ionization energy is always endothermic, that is energy is added to the atom to remove the electron.
Trend in Ionization Potential Trend in Ionization Potential Ionization potential: The energy required to remove the valence electron from an atomic specie. Largest toward NE corner of PT since these atoms hold on to their valence e- the tightest.
Ionization Energy (Potential) Draw arrows on your help sheet like this:
Electron Affinity What does the word affinity mean? Electron affinity is the energy change that occurs when an atom gains an electron (also measured in kJ). (now, were making ANIONS) Where ionization energy is always endothermic, electron affinity is usually exothermic, but not always.
Electron Affinity Electron affinity is exothermic if there is an empty or partially empty orbital for an electron to occupy. If there are no empty spaces, a new orbital or PEL must be created, making the process endothermic. This is true for the alkaline earth metals and the noble gases.
Trend in Electron Affinity Trend in Electron Affinity Electron Affinity: The energy release when an electron is added to an atom. Most favorable toward NE corner of PT since these atoms have a great affinity for e-.
Electron Affinity Your help sheet should look like this: ++
Summary of Trends Periodic Table and Periodic Trends 1. Electron Configuration 2. Atomic Radius: Largest toward SW corner of PT 3. Ionization Energy: Largest toward NE of PT 4. Electron Affinity: Most favorable NE of PT
Metallic Character This is simply a relative measure of how easily atoms lose or give up electrons. Your help sheet should look like this:
Electronegativity Electronegativity is a measure of an atoms attraction for another atoms electrons. It is an arbitrary scale that ranges from 0 to 4. The units of electronegativity are Paulings. Generally, metals are electron givers and have low electronegativities. Nonmetals are electron takers and have high electronegativities. What about the noble gases?
Electronegativity Your help sheet should look like this: 0
Overall Reactivity This ties all the previous trends together in one package. However, we must treat metals and nonmetals separately. The most reactive metals are the largest since they are the best electron givers. *chumps* The most reactive nonmetals are the smallest ones, the best electron takers. *thieves*
Overall Reactivity Your help sheet will look like this: 0
Ionic Radius Cations are always smaller than the original atom. Having lost one child, the nucleus holds the rest of her children tightly! Conversely, anions are always larger than the original atom. When extra electrons are added to the outer PELs, the nucleus cant hold on as tightly!
Cation Formation 11p+ Na atom 1 valence electron Valence e- lost in ion formation Effective nuclear charge on remaining electrons increases. Remaining e- are pulled in closer to the nucleus. Ionic size decreases. Result: a smaller sodium cation, Na +
Anion Formation 17p+ Chlorine atom with 7 valence e- One e- is added to the outer shell. Effective nuclear charge is reduced and the e- cloud expands. A chloride ion is produced. It is larger than the original atom.
Summary Periodic Table Periodic Table: Map of the Building block of matter Type Type: Metal, metalloid and Nonmetal Groupings: Representative or main, transition and Lanthanide/Actanides Family Family: Elements in the same column have similar chemical property because of similar valence electrons Alkali, Alkaline, chalcogens, halogens, noble gases Period: Period: Elements in the same row have valence electrons in the same shell.
The periodic table is the most important tool in the chemists toolbox!
Where do Elements Come From? All matter is made up of atoms -- elements comprised of smaller particles such as protons, neutrons, and electrons. The number of protons within the nucleus -- the central component of the atom -- determines the type of element. An element can have different forms, called isotopes, based on the number of neutrons in the nucleus. For example, an ordinary hydrogen nucleus contains just one proton. But deuterium, an isotope of hydrogen, has one proton and one neutron in its nucleus.
The entire universe shares a common set of elements. In the very early universe, the only elements were hydrogen and helium. But since the formation of stars, lighter elements within the stars began fusing to create heavier elements, producing all the other naturally occurring elements. Under the extremely high temperatures and pressures within the core of stars, atoms collide at high enough speeds to overcome the usual electromagnetic repulsion of nuclei, allowing nuclear fusion to occur.
All stars live by fusing hydrogen into helium. In the first step of the process, two hydrogen atoms fuse to form deuterium. In the next step, another hydrogen atom fuses with the deuterium, creating a rare isotope of helium that has two protons and one neutron in its nucleus. In the third step, two of the rare helium atoms fuse to create a single normal helium atom and two hydrogen atoms. The fusion pathway described above requires six hydrogen atoms to create one helium atom -- however, there are two hydrogen atoms left over at the end of the process. The net result is that it takes four hydrogen atoms to make one helium atom. The energy that fuels a star is a result of the difference in mass between the original four hydrogen atoms and the resulting helium atom. Following Einstein's mass-energy relationship, E=mc2, the missing mass is converted to energy.
At even higher temperatures and pressures, heavier elements are able to form. Many are made from a process called "helium capture," in which a heavier element fuses with a helium atom. For example, helium fuses with carbon to make oxygen, and helium fuses with oxygen to make neon. Heavier nuclei can also fuse with each other, such as when carbon and oxygen fuse to make silicon or two silicon atoms fuse to make iron. Eventually, the interior of a massive star begins to resemble an onion, with different elements being created in different layers. However, elements heavier than iron are only produced in the extraordinary conditions created by the collapse and explosion of a star -- a supernova.
The Elements: Forged in Stars
Discussion Questions How does a star get its energy to glow? What elements make up young stars? What causes a star to become a supernova? Why do you think it takes a tremendous amount of heat and pressure to create helium (and then carbon, etc.)? What could you infer about the age of a star if you were to find evidence of iron being present?
Islands of Stability An element is defined according to the number of protons contained inside the nucleus of each atom. No two elements have the same number of protons, hence each element has a unique atomic number. The periodic table lists 90 naturally occurring elementsmeaning those created in the aftermath of the Big Bang or later forged in the heat and pressure of stars. A further 28 elements have been created by humans in a laboratory setting.
The higher its atomic number, the heavier and less stable an element is. Elements are considered stable when the repulsive force that exists between positively charged protons is effectively countered by another force, the strong nuclear force, which corrals protons and chargeless neutrons and prevents them from bursting out of the nucleus. Heavy elements are unstable because their atoms contain lots of protons. While the strong force is about 100 times stronger than the electromagnetic repulsion between two protons, it is a short-range force. The electromagnetic force begins to overwhelm the strong force as the number of protons in a nucleus approaches 100 and the nucleus becomes over-large. When breakup, or decay, occurs, the energy pent up inside the nucleus is released in the form of radiation and a spray of particles.
Scientists have proven that it is possible to create new heavy elements artificially by taking an existing element and adding protons and neutronstogether called nucleonsto its nucleus. Frequently, they do this by bombarding an atom with nucleons with the hope that these nucleons are successfully incorporated into the nucleus. But as more protons are added to a nucleus, their tendency to repel one another gets stronger and stronger. Consequently, experimental heavy atoms tend to rip apart almost instantaneously. Their very brief existence makes it difficult for scientists to study their characteristics for potential applications in science.
The nuclear chemists trying to create element 114 are hopeful that this heavy atom would be longer-lived. Since the 1950s, scientists have viewed atomic nuclei as being built up in rings, a model similar to that of electron shells within the atom. According to this revised model, a ring filled with very precise numbers of protons and neutrons would give an element stability, even if elements nearby on the periodic table were highly unstable. For example, certain forms, or isotopes, of thorium (atomic number 90) and uranium (92) are the only naturally occurring atoms heavier than bismuth (83) that are relatively stable amidst other, far less stable elements. The elusive element 114 discussed in this video segment is, hypothetically, another "island of stability" in a "sea of instability." Scientists just have to find a way to get the "magic numbers" of 114 protons and 184 neutrons inside a nucleus.
Islands of Stability
Discussion Questions What explanation is proposed for the observation that protons with like charges (+) can stay close together in the nucleus of an atom? Why don't they repel each other right out of the nucleus? What is meant by the "island of stability"? Why is it called an island? What reasoning did the scientists use to predict the properties of element 114? Why do you think it is so very difficult to have a direct collision between nuclei? Is it something to do with the size of the particles? Their charge? What other combinations of two elements would, mathematically at least, yield the nucleus of element 114?
Beyond the Atom Today I will show several short video clips. Some you may have seen before. They have to do with further topics in atomic structure and nuclear science. Spread throughout the room are six short essays with discussions. You must choose AT LEAST TWO separate discussion questions, and compose a full answer (TAG where possible). This will be a graded assignment. If you listen to the videos, your assignment will be easier.