Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Alkaline earth metal wikipedia , lookup
Group 12 element wikipedia , lookup
Boron group wikipedia , lookup
Livermorium wikipedia , lookup
Group 3 element wikipedia , lookup
Period 6 element wikipedia , lookup
Period 5 element wikipedia , lookup
Period 3 element wikipedia , lookup
The Periodic Table Chapter 6 Chemistry At the end of the 1700’s, only about 30 elements had been identified. Included in this were the elements that had been known since ancient times like Cu and Au. In less than 100 years the number of elements had doubled, and scientists needed a better way of classifying them. Antoine Lavoisier Late 1790s Compiled a list of the 23 known elements In the 1800s the list exploded as more and more elements were discovered. J. W. Dobereiner Early 1800’s Organized elements in groups of 3 called triads. He based his triads on similarities in properties between elements. 2 of his triads were Li, Na, & K and Cl, Br, & I. Within the triads the middle elements often had properties that were approximately the average of the 1st & 3rd elements. John Newlands 1864 Noticed when he arranged the elements in order of increasing atomic mass, their properties repeated every eight element. The first & eighth elements had similar properties Periodic: a pattern that repeats itself in a specific manner John Newlands Called his observations the “Law of Octaves” b/c an octave in music is a group of notes that repeats every eighth tone. Acceptance of this law did not last very long b/c it didn’t work for ALL of the known elements. He was basically correct though – the properties of elements do repeat in a periodic way. Dmitri Mendeleev & Lothar Meyer Demonstrated a connection between atomic mass & elemental properties. Mendeleev is given more credit b/c he published his organization scheme first & demonstrated its usefulness. Mendeleev’s Periodic Table Dmitri Mendeleev Mendeleev By Michael Offutt He was born in Russia in 1834 Hard work as a youth opened up the college doors. He always tried to be the best that he could be, And chose to make his mark in Chemistry. Chorus: Who told the elements where to go? Mendeleev! Who put them in columns and in rows? Mendeleev! Who was ready, who was able to make a periodic table, Who was that chemist? Mendeleev! He wondered if nature really had a master plan If the elements had a pattern that one could understand, So he bought a bunch of cards and on each one wrote the name, Of an element and its weight, and then he played the game. He put them all in order by their atomic weights, Used their chemical properties to differentiate. Groups began to form and despite some question marks, He managed to produce a simple periodic chart. Chorus At first in 1869 the chart was not a hit, But that young Russian chemist was not the kind to quit. He revised atomic weights and staked his whole career, Predicting that several new elements would appear. A few years passed and sure enough they came, Gallium, scandium, germanium were their names. Chemists everywhere were impressed with what they saw. There really must be something to this periodic law. So they call him the father of the periodic table, And his work gave rise to another kind of label. It’s the name for elements number 101, In honor of this man they call it Mendelevium. Chorus Dmitri Mendeleev Russian Chemist Placed element’s atomic mass and properties on cards Arranged elements looking for trends When arranged in order of increasing atomic mass, similar properties appeared at regular intervals. Dmitri Mendeleev Created a table published in 1869 Several empty spaces in his table. In 1871, he boldly predicted the existence of several elements. By 1886 all three were discovered! The success of his predictions led to the acceptance of his periodic table. Dmitri Mendeleev His periodic table is NOT entirely correct. Several order. elements were not in correct Henry Moseley 1911 Discovered why a few elements could not be arranged according to their atomic masses. Led to the current arrangement of the current Periodic Table by atomic number. This arrangement allowed a clear pattern of periodic patterns. Still used today! The Modern Periodic Table Groups: columns on the periodic table. Also referred to as families Periods: rows on the periodic table Janet Periodic Table Modern Russian Table Chinese Periodic Table Stowe Periodic Table Benfey Spiral Periodic Table Triangular Periodic Table “Mayan” Periodic Table The Mayan Periodic Table of Elements, named for its similarity to an ancient calendar, is based on electron shells. The shells are shown as concentric circles and the elements with completed shells are arranged vertically from the center to the top of the circle. Giguere Periodic Table Play the Element Song http://privatehand.com/flash/elements.html Three Major Groups of Elements 1. Metals: shiny, smooth, good conductors. Solid at room temperature. Most are malleable & ductile. 2. Nonmetals: gasses or brittle solids, poor conductors, only liquid is bromine 3. Metalloids: elements with properties of metals and nonmetals. (Also called semimetals) The Periodic Law The properties of the elements are periodic functions of their atomic numbers. Main Families: Be able to identify. Alkali Metals: Group 1A Alkaline Earth Metals: Group 2A Transition Metals: Group B elements Inner Transition Metals: Lanthanides & Actinides – bottom rows of the periodic table Halogens: Group 7A – highly reactive Noble Gases: Group 8A – extremely nonreactive Elements in the same family have similar properties because their outer electron configurations are the same Representative Elements These are the elements in the s & p-blocks of the periodic table. They display the entire range of elemental characteristics found on the periodic table. Periodic Table with Group Names Periodic Trends As you compare elements from left to right across the periodic table, you will notice a trend or regular change in a number of properties due to the periodic law. Trends to learn: Atomic radii Ionic radii Ionization energy Electronegativity Electron Affinity Metallic Character Show the trends on your periodic table. Atomic Radii Atomic radius – one half the distance between the nuclei of two atoms of a molecule. Atomic Radii Decrease across the periods. Caused by the increasing positive charge of the nucleus Increase down the group ( A few exceptions) electron is in higher energy levels – farther from the nucleus. Outer Group trends As we go down a group Each atom has another energy level, So the atoms get bigger. H Li Na K Rb Ionic Radii Ion: an atom or a bonded group of atoms that has a charge Cation – positive ion Loss of electron; decrease in radius Due to loss of valence electrons, there might be an empty orbital, and less repulsion between electrons means they can be pulled closer to the nucleus Ionic Radii Anion – negative ion Gain of electron; increase in radius More electrons around the nucleus means a greater repulsion between electrons, so they spread out more Ionic Radii Metals on the left form cations Nonmetals on the right form anions As you move to the right on the Periodic Table, the size decreases. As you move down a column, the size increases Ionization Energy Ionization energy – energy required to remove an electron from a neutral atom Ionization Energy Across the periodic table the ionization energy increases. Caused by the increasing positive nuclear charge which attracts electrons more strongly. This results in more energy required to remove an electron. Down the Groups, the ionization energy decreases. Caused by the increased size of the atoms. The electrons that are farther from the nucleus are easier to remove. Ionization Energy Another Way to Look at Ionization Energy Electronegativity Electronegativity – the relative ability of an atom to attract electrons in a chemical bond Across the periodic table electronegativity increases. Elements on the right of the table tend to gain electrons – have higher electronegativities Down a group electronegativity decreases. Electrons are farther away from the nucleus so there is less attraction to the nucleus Electron Affinity Electron affinity is a measure of an atom′s ability to gain an electron. It increases across a period because the increasing positive nuclear charge attracts electrons more strongly. Electron affinities generally become smaller down a column of the periodic table. The electron being added to the atom is placed in larger orbitals, where it spends less time near the nucleus of the atom. Metallic Character The metallic character of an element can be defined as how readily an atom can lose an electron. From right to left across a period, metallic character increases because the attraction between valence electron and the nucleus is weaker, enabling an easier loss of electrons. Metallic character increases as you move down a group because the atomic size is increasing. When the atomic size increases, the outer valence shells are farther away. The electrons of the valence shell have less attraction to the nucleus and, as a result, can lose electrons more readily.