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The Periodic Table Dimitri Mendeleev • Russian scientist developed the first published table in 1869. • Arranged elements in order of atomic mass • Elements with similar properties were placed in columns • left spaces for undiscovered elements Periodic Law the pattern of the table • Mendeleev’s table was called a periodic table because…….. • If the elements were arranged in order of increasing atomic mass then elements with similar properties would show up PERIODICALLY. Henri Moseley (1914) • Used X-rays to reveal atomic numbers of several elements. • Suggested that the elements should be arranged in order of atomic number instead of atomic mass. – Today that is how it is arranged Reading the Periodic Table • Families or Groups – Up and down • Numbered 1 to 18 • Elements in groups (families) have similar characteristics • Periods –Across the table 1-7 Classifications of Elements Metals Non-metals Metalloids (semi-metals) Metals • Elements to the left of the steps • except H, Ge & Sb Ge Metals Sb Metal characteristics • Solids at STP (except mercury) • good conductors of electricity and heat – Mobile electrons • • • • shiny luster ductile - drawn (made) into wire malleable - hammered into sheets when combined in compound have a positive oxidation state (+, cation) • Metallic character increases R to L – Most reactive metals found in Group 1 Non-metals 18 H B Si As Te Non-metal characteristics • • • • • Solid, liquid or gas at STP used as insulators solids are dull brittle when combined in a compound have negative oxidation state (-, anion) • Metallic character decreases L to R Metalloids • a.k.a. Semimetals • both metal and non-metal properties • “sit on the steps” • 2 hide underneath B Si Ge As Sb Te Elements are (s), (l) & (g) • Solid – particles have vibratory motion and are tightly packed – Almost ALL of the elements • Liquid – particles can move throughout substance – particles are farther apart than in solids – conforms to shape of container – ONLY Hg and Br • Gas – molecules in constant, random, straight line motion – molecules fill container – large space between “volumeless” molecules – conforms to the shape of the container – H, N, O, F, Cl and Group 18 Allotropes • Different forms of an element found naturally in the same state – Different molecular structures Carbon diamond, coal, graphite Oxygen O2 & O3 Diatomic elements • Elements found bonded to itself “uncombined” H N • N2 O2 F2 Cl2 Br2 I2 and H2 O F Cl Br I Monoatomic elements • Inert • Don’t react or form compounds 18 He Valence shell filled with 2e- Ne Ar Kr Xe Rn Valence shell filled with 8 e- Valence electrons • The number of valence electrons correspond to group number • 1, 2 , 13 - 18 Last digit • The Energy Level (shell) they are in is the same as the period # Group / Family Characteristics Each group has characteristic properties that are directly related to electron configuration & especially the number of valence electrons Group 1 • • • • Alkali Metals all elements except hydrogen most reactive metal group SO reactive they are never found alone in nature – always bonded to another element • form +1 ions Group 2 • Alkaline Earth Metals • second most reactive metals group • SO reactive they don’t occur alone in nature – always bonded to another element • form +2 ions d- block elements • Transition Metals COLORful ions and solutions • Transition metals not as reactive as other metals • some found in free state – Au, Ag, Pt • multiple positive oxidation states – Iron (IV) oxide FeO2 – Iron (II) oxide FeO Group 17 • Halogens • Most reactive nonmetal group • SO reactive that they don’t occur by themselves in nature – at least bonded to themselves (diatomic) • form -1 ions Group 18 • Noble gases • “Inert” gases • don’t like to combine with other elements – Valence shells filled Ionization Energy Ionization Energy (first) • Definition: – energy needed to remove the most loosely held eValence electron high E electron Outermost electron What’s holding the e- in place? • Nuclear charge – There is a force of attraction between protons (+) in the nucleus and electrons () in the orbitals – “Opposites attract” Ionization energy • Hint: energy needed to make an ion by losing electrons MOST elements want 8 e(octet rule) • Elements with only a few valence electrons will tend to have lower ionization E • In other words… Metals – It doesn’t take a lot of E to remove their e- MOST elements want 8 e(octet rule) • Elements with almost 8 valence electrons won’t give them up so easy – It takes a lot of E to remove their e- • Non-metals have high Ionization E Who has the highest IEs? Graph Ionization Energies • Label X axis with Atomic #1-20 • Label y axis with 1st IE (KJ/mol atoms) • AFTER you plot the points – Label data points with element symbols – Connect data points of same period only – Separate your graph into Periods He Period 1 Period 2 Period 3 Period 4 First Ionization Energy (KJ / mol) Ne Ar H Ca Li Na What is the periodic trend for ionization energy? INCREASES Ionization E trend? • As move across a period…IE increases. WHY? 3 p+ 9 p+ • As you go across a period – a large proton and a tiny electron are being added. – more p+ hold the e- tighter • As move UP a group … IE increases. WHY? Period 1 Period 2 Period 3 Period 4 Let’s figure it out . . . Potassium 19 p+ + Sodium 11 p+ + Lithium 3 p+ + INCREASES because ... • As you go up a group – the valence shell gets closer to the nucleus and can hold on to the etighter. SHIELDING • Reason why IE decreases as you go down a group • the distance increases between the p+ and valence e– AND • e- in outer shells repel each other –WHICH IS WHY low IE are so reactive! Electronegativity • Ability of an atom to attract electrons of other atoms. • In other words. . . – Atoms with high e-neg are bullies that steal electrons Electronegativity Graph Fluorine Electronegativity • Determine the periodic trend F INCREASES EXCEPT for Noble gases. WHY? Atoms with high electronegativities also have high ionization E Atomic Radius • Radius – distance from the center of a circle (Nucleus) to the outermost edge (valence shell) R Atomic Radius Periodicity D E C R E A S E S DECREASES Why????? • Why does atomic radius DECREASE as you move up a group? • Losing layers of e• Why does atomic radius DECREASE as you move across a period? • Increasing the # of p+ holds the e- in tighter • Increasing NUCLEAR CHARGE • What happens to atomic radius as you create a + ion? • radius decreases • What happens to atomic radius as you create a - ion? • radius increases • Compare the ionic radus of Mg2+ and the atomic radius of Ne. The radius of the Mg2+ ion is smaller than the atom of Ne, because the Mg2+ ion has more p+ (12) than the Ne atom (10). Compare . . . • Fluoride ion & Fluorine atom • Sodium ion & Sodium atom • Fluoride ion & Neon atom General Formulas of compounds • You can look at the groups on the periodic table and determine how they will combine with elements of different groups. Write these formulas • • • • • • lithium fluoride • What do you notice? sodium fluoride potassium fluoride • Write the general formula for Group 1 lithium chloride and Group 17 sodium chloride elements potassium chloride AB Write these formulas • • • • • • beryllium fluoride magnesium fluoride calcium fluoride beryllium chloride magnesium chloride calcium chloride • What do you notice? • Write the general formula for Group 2 and Group 17 elements AB2 Write these formulas • • • • • • lithium oxide sodium oxide potassium oxide lithium sulfide sodium sulfide potassium sulfide • What do you notice? • Write the general formula for Group 1 and Group 16 elements A 2B Write these formulas • • • • • • beryllium oxide magnesium oxide calcium oxide beryllium sulfide magnesium sulfide calcium sulfide • What do you notice? • Write the general formula for Group 2 and Group 16 elements AB Formula Writing & Naming Review • • • • • • • Lead IV oxide Phosphorus pentoxide SO3 Oxygen Argon Aluminum oxide NiO Different Forms of the Periodic Table • Changes were made to Mendeleev’s table to look like the modern Periodic table we use today. • This is not the only form of the periodic table that exists, however it is the most widely accepted. Stowe’s Physicists p.t. Benfey p.t. Zmaczynski p.t. Alexander Arrangement p.t. 立体周期表の組み立て方 p.t. THE END