Chapter 4 Development of the Periodic Table –Mendeleev vs Moseley Mendeleev (Mid 1800’s) –Discovered a repeating pattern as he arranged elements by atomic mass. (Every seventh element had similar behavior, color, etc) – This is due to periodic properties (when things repeat regularly) –Valence electrons gained or lost (outermost electrons in an atom responsible for behavior) repeated –Left gaps for missing elements –Didn’t include noble gases (inert gases) because he didn’t know they existed because they don’t react with things

Chapter 4 Moseley (early 1900’s) –Fixed Mendeleev’s errors by adding in missing elements –Added noble gases –Discovered elements atomic number and arranged by this which fixed some misplacements

Chapter 4 Notes Trends on Period Table –Atomic Radius – Size of the atom, increases as you go down a group and decreases as you move across a period b/c the electrons are held more tightly by the nonmetals. –Ionization Energy – Energy required to remove an electron to make the atom an ion. Increases as you move up and the right. Fluorine has highest, Francium is the lowest. –Electron Affinity – Want for more electrons, follows the same trend as ionization energy.

Chapter 4 Notes Need to know the families of the periodic table –Alkali Metals (1) –Alkaline Earth Metals (2) –Transition Metals (3-12) –Boron Family (13) –Carbon Family (14) –Nitrogen Family (15) –Oxygen Family (16) –Halogens (17) –Noble Gases (18)

Chapter 4 Active metals (Groups IA/1 and IIA/2) –Alkali metals (Group IA) included Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium. They are the most active metals on the table. They are close to noble gas status so they react quickly to get there. Soft metals that can be cut with a knife, rarely found in nature b/c they react with water violently. Only contain one valence electron (+1 Charge)

Chapter 4 Alkaline Earth Metals (Group 2/IIA) –Contain Berylium, Magnesium, Calcium, Strontium, Barium, and Radium –Metals that are often needed by the body for health, used in medicines, also burn pretty easily (photography, flares, fireworks) –2 valence electrons – give them up to become stable (+2 charge) –Not quite as reactive as group 1

Chapter 4 Transition Metals (Group 3-12) –Metals that don’t fit into a particular family. –Excellent conductors, good for jewelry and building materials due to high density and strength. –Have 2 valence electrons so they tend to be a +2 charge however some give up more. –Fairly stable metals!

Chapter 4 Metals to Nonmetals (Groups IIIA/13 to Group VIA/16) Boron family (contains Boron, Aluminum, Gallium, Indium, Thallium) –Top behave more like non metals and as you go down they become more metallic –3 valence electrons (+3 Charge) –Good for alloys, more heat resistant, form oxides

Chapter 4 Carbon Family (Group 14) –Contains – Carbon, Silicon, Germanium, Tin, Lead –Again become more metallic as you move down the column –Have 4 Valence electrons (+4 or –4 charge) –Most versitale group, many bonding sites, Carbon most important in this group to us –Silicon good for computer chips

Chapter 4 Nitrogen Family (Group 15) –Contains – Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth –Nonmetal at top to metal at bottom –5 valence electrons (easier to gain 3 electrons than lose 5 = -3 charge) –Somewhat reactive group, uses include fertilizers, explosives, drugs and dyes

Chapter 4 Oxygen Family (Group 16) –Contains – Oxygen, Sulfur, Selenium, Tellurium, and Polonium –More reactive than group 15 –Have 6 valence electrons (-2 charge) –Needed by body, used to make many compounds, drugs, matches, gun powder, alloys.

Chapter 4 Halogens (Halogen means salt forming) (Group 17) –Include elements Fluorine, Chlorine, Bromine, Iodine, Astatine –Have 7 Valence electrons – Most reactive Nonmetals (-1 charge) –Good for disinfectants, Diatomic elements (Bond to themselves), Form salts

Chapter 4 Noble Gases (Group 18) –Contain Helium, Neon, Argon, Krypton, Xenon, Radon –Have a full valence shell (8 electrons) = Non reactive (Inert) –Neon signs, balloons/blimps, cancer treatment, photography

Chapter 4 Notes 4 forces acting within an atom * Electromagnetic force – Holds electrons to atom because of attraction of opposite charges * Strong Force – between protons, keeps protons from repelling and breaking up nucleus * Weak force – Radioactive decay, breaking of an atom over time * Gravity – Attraction to mass

Chapter 4 Notes Moles, Mass, Molecules Conversions -Based on Formula Mass (mass from periodic table for each element) compounds require us to add mass of each part to get total mass. -Example H2O -Hydrogen has a mass of 1 and we have 2 of them so 1*2=2 -Oxygen has a mass of 16 and we have 1 of them so total mass = 2+16=18

Chapter 4 Notes Formula mass is the mass found in one mole of a substance. It is based on Avegadro’s number (6.02*10 23 ) Number of molecules in 1 mole.