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Periodic Table PBL: Period 5, Group 2
Transcript of Periodic Table PBL: Period 5, Group 2
[(mass of isotope) (%abundance) ] + [(mass of isotope) (%abundance)] + [….]/100% Group 2: Alkaline Earth Metals Atomic radii (measure of the size of the atoms from nucleus to electron cloud boundary):
As you go down the group, the atomic radii of the elements get larger. Ex: Calcium- 197 pm while Radium- 283 pm Period 5 Strontium has 4 isotopes with the following masses: 83.9134 amu (.56%), 85.9094 (9.86%), 86.9089 (7%) and 87.9056 (82.58%). Calculate the atomic mass of strontium. 83.9134*(0.56/100)+85.9094*(9.86/100)+ 86.9089*(7/100)+87.9056*(82.58/100)
=87.62 amu Average Atomic Mass Calculation for Calcium:
[(mass of isotope) (%abundance) ] + [(mass of isotope) (%abundance)] + [etc….]/100%
0.9694 (40.008) = 38.78376 (C-40)
+ 0.00647 (41.885) = .27099 (C-42)
+ 0.00135 (42.991) = .05804 (C-43)
+ 0.02086 (43.599) = .90948(C-44)
+ 0.00004 (45.988) = .00184 (C-46)
+ 0.00187 (47.999) = .08976 (C-48)
= 40.114 amu Rubidium: Rubidium also follows the trend of increasing reactivity as the atomic number increases in the alkali metals, for it is more reactive than potassium, but less so than cesium. Strontium: Strontium is a soft metal and is extremely reactive upon contact with water. If it does come in contact with water, though, it will combine with the atoms of both oxygen and hydrogen to form strontium hydroxide and pure hydrogen gas Yttrium: Yttrium is almost always found combined with the lanthanides in rare earth minerals and is never found in nature as a free element. Zirconium: Zirconium forms a variety of inorganic compounds such as zirconium dioxide and zirconocene dichloride Niobium: Niobium is used mostly in alloys, the largest part in special steel such as that used in gas pipelines Molybdenum: It readily forms hard, stable carbides, and for this reason it is often used in high-strength steel alloys. Molybdenum does not occur as a free metal on Earth, but rather in various oxidation states in minerals Bonding:
Has 2 outer valence electrons, making it easy to bond with
Mostly ionic bonds (transfer of electrons)
EX: Beryllium diflouride (BeF2), Magnesium sulfide (MgS), Calcium peroxide (CaO2), Strontium selenide (SrSe), Barium dichloride (BaCl2), Radium oxide (RaO) Technetium: Nearly all technetium is produced synthetically and only minute amounts are found in nature. Naturally occurring technetium occurs as a spontaneous fission product in uranium ore or by neutron capture in molybdenumores Ruthenium: Ruthenium usually occurs as a minor component of platinum ores Rhodium: Palladium, platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). These have similar chemical properties, but palladium has the lowest melting point and is the least dense of them. Ionic radius (measure of an atom's ion in a crystal lattice) gets larger as you go down the group.
Calcium 2+ ionic radius is 99 pm while Radium 2+ ionic radius is 162 pm. Silver: The metal occurs naturally in its pure, free form (native silver), as an alloywith gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc refining. Cadmium: Like zinc, it prefers oxidation state +2 in most of its compounds and like mercury it shows a low melting point compared to transition metals. Indium: Zinc ores continue to be the primary source of indium, where it is found in compound form. Tin: This silvery, malleable post-transition metal is not easily oxidized in air and is used to coat other metals to prevent corrosion. The first alloy was bronze, an alloy of tin and copper Reactivity: The alkaline earth metals are very reactive because they have only two outer valence electrons. However they are not as unstable as the akali metals in Group 1. Antimony: Antimony compounds have been known since ancient times and were used for cosmetics, metallic antimony was also known but mostly identified as lead Tellurium: Its extreme rarity in the Earth's crust, comparable to that of platinum, is partly due to its high atomic number, but also due to its formation of a volatile hydride which caused the element to be lost to space as a gas during the formation of the planet Iodine: Iodine and its compounds are primarily used in nutrition, and industrially in the production of acetic acid and certain polymers Xenon: Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized Electronegativity(measure of the attraction to form a chemical bond): Decrease from top to bottom
EX: Beryllium has an electronegativity of 1.5 while Barium has an electronegativity of 0.9 Ionization energy (amount of energy to remove an electron): Decreases from top to bottom; low ionization energy because Group 2 only needs to lose 2 electrons to form a stable octet
EX: Beryllium- 899.243 kJ/mol while Radium (last element in Group 2)- 509.153 kJ/mol The alkaline earth metals of Group 2 each have two outer valence electrons which makes them highly reactive and thus usually not found in elemental form but in a compound. Group 2 always has the electron configuration of ns2. (n being the number of s blocks) The Lewis structures of the Group 2 elements will always consist of the element symbol with 2 dots to indicate 2 outer valence electrons.
EX: Being metals, the state of matter at room temperature of these elements are solid. The alkaline earth metals have very high boiling and melting points due to the compactness of their crystal lattice. In general, the boiling and melting points decrease down the Group as the elements become less metallic in nature.
EX: Beryllium- Melting point: 1278 Celsius
Boiling point: 2469 Celsius
Calcium- Melting point: 842 Celsius
Boiling point: 1484 Celsius, All of the elements in Group 2 are metals. Atomic Radii: In period 5, the atomic radii increase, decrease and then slightly increase again from left to right. Ionic Radii: The radius of an atom's ion.
As you move across a row of period of the periodic table, the ionic radius decreases for metals forming cations, as the metals lose their outer electron orbitals. The ionic radius increases for nonmetals as the effective nuclear charge decreases due to the number of electrons exceeding the number of protons. Electron affinity (ability to accept an electron measured by the energy change when an electron is added)- The alkaline earth metals have a low electron affinity because most of the time, they lose electrons rather than accept electrons. Reactivity:
Rubidium is the first element placed in period 5. It is an alkali metal, the most reactive group in the periodic table
Strontium is the second element placed in the 5th period. It is an alkaline earth metal, a relatively reactive group
(all reactivities vary across the row) Electronegativity: ex. Rb = 0.82 and Cd = 1.69
Electronegativites vary across the row Ionization Energy: The ionization energy of an atom is the amount of energy that is required to remove an electron from a mole of atoms in the gas phase ex. Sn = 709 kJ/mol and I = 1008 kJ/mol
(kilojoules per mole) Electron Configuration:
As a rule, period 5 elements fill their 5s shells first, then their 4d, and 5p shells, in that order, however there are exceptions, such as rhodium. Sr = 200 and In = 155 Valence Electrons: The number of valence electrons increase as you move across period. Lewis Structures: In period 5, the Lewis structures would just be the element name (ex. Ag) and then the number of valence electrons it has. The valence electrons increase as you go from left to right, so Rb would have less dots than I. States of Matter: Because the elements in period 5 exist in all three sections, some are solids, and some are gasses. Boiling/ Melting point:
The stronger the forces that act between molecules of a substance, the higher the melting point tends to be.
Ag = melting point = 1235.08 K, 962 ºC, 1571 ºF
boiling point = 2485.15 K, 2212 ºC, 3571 ºF
I = Melting Point: 113.5 °C - 386.65 °K
Boiling Point: 184.0 °C - 457.15 °K There are metals and metalloids in period 5.
Examples of metalloids would be Antimony and Tellurium. Works Cited
"Physical properties of Alkaline earth metals | Melting and boiling point of Alkaline earth metals | Reducing character of Alkaline earth metals | Solubility of Alkaline earth metals | IIT JEE Chemistry | IIT JEE Study Material." IIT JEE AIEEE Online Coaching, Engineering Exam Preparation - askIITians.com . N.p., n.d. Web. 20 Dec. 2012.
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"Group IIA: Alkaline Earths." Chempaths. N.p., n.d. Web. 20 Dec. 2012. <http://chemed.chem.wisc.edu/chempaths/GenChem-Textbook/Group-IIA-Alkaline-Earths-605.html>.
"Group Trends: The Active Metals." Welcome to MikeBlaber.org. N.p., n.d. Web. 20 Dec. 2012. <http://www.mikeblaber.org/oldwine/chm1045/notes/Periodic/MTrends/Period07.htm>.
Helmenstine, Anne Marie, and Ph.D.. "Periodic Properties of the Elements." About.com Chemistry - Chemistry Projects, Homework Helm, Periodic Table. N.p., n.d. Web. 20 Dec. 2012. <http://chemistry.about.com/od/periodictableelements/a/periodictrends.htm>.
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