Unit 2 Chapter 12 The Periodic Table

Arranging the Elements Dmitri Mendeleev Russian chemist 1869 Wrote names and properties of known elements on cards Arranged his cards by different properties – Density, melting point, appearance

Arranging the Elements Mendeleev saw patterns in his arrangement Increasing atomic mass = similar properties Periodic – happens at regular intervals There were missing elements in his patterns He could predict what the properties of the unknown elements by comparing to similar elements

Changing the arrangement Some properties didn’t fit the pattern Need to use atomic number, not atomic mass Henry Mosely in 1914

Periodic Table of Elements

Classes of Elements Metals – Most elements are metals – Few electron in outer level – Solid at room temperature (Hg) – Shiny, ductile, malleable, conductive – Fe, Cu, Zn, Au, Ag, Pt, W, U

Classes of Elements Nonmetals – To the right of the zigzag line – Mostly complete outer level of electrons – Noble gases – Half are solid at room temperature – Half are gases or liquids – Not malleable, ductile, or conductive – S, C, N, O, Cl, Ne, Kr

Classes of Elements Metalloids – Along zigzag line – Semiconductors – Half full outer level of electrons – Some properties of metals, some of nonmetals – Te, B, Si, Sb, As

Code in Periodic Table Chemical symbols – One or two (sometimes three) letters – First letter is always capitalized – Second letter is lowercase – Naming After scientists – Es, Cm, Md, No After places – Am, Cf, In, Eu After Latin or Greek root words – Cr, Ti, U, Pu

Code in Periodic Table Each ROW (going across) is called a Period – Similar physical and chemical properties – Conductivity and reactivity change gradually Each COLUMN (going down) is called a Group – Similar physical and chemical properties – Electron levels are same going down the group – Also called a family

Grouping the Elements Shared properties Same number of electrons in outer energy level Atoms want to fill up their outer level with electrons

Group 1 Alkali metals – Most reactive metals – Atoms give away 1 electron – Usually stored in oil (NOT WATER!!!) – Only found in combination with other elements in nature (NaCl, KBr) – Soft, can be cut with a knife – Sparks and burns when mixed with water

Group 2 Alkaline Earth metals – Less reactive than alkali metals – Give away 2 outer level electrons – Mixes with other elements fairly easy – Mg, Ca, Ba

Groups 3-12 Transition metals – These groups do not have specific names – All called transition metals – Do not give away electrons easy – Less reactive – Middle of periodic table – Usually shiny, conduct heat and electricity

Lanthanides and Actinides Special group part of transition metals Very bottom of periodic table Lanthanides – Follow lanthanum – Shiny, reactive Actinides – Follow actinium – All are radioactive (unstable) – All after plutonium are man-made (not in nature)

Group 13 Boron group Has 3 outer level electrons Aluminum (most abundant metal in Earth’s crust) Reactive Solids at room temperature

Group 14 Carbon group 4 outer level electrons Fairly stable, doesn’t react easily C, Si, Sn, Pb

Group 15 Nitrogen group 1 gas, rest are solids N is most abundant gas in atmosphere N is not very reactive, P is very reactive N, P, As, Sb, Bi Wants to take 3 electrons from other elements

Group 16 Oxygen group 1 gas, rest are solids Wants to take 2 electrons from other elements O is used in living organisms S smells like rotten eggs (lit matches)

Group 17 Halogens 2 gases, 1 liquid, 2 solids Extremely reactive Want to take 1 electron from other elements Forms salts Never found in nature by themselves

Group 18 Noble gases Also called inert gases All are gases NONREACTIVE!!! Don’t want to give or take any electrons Neon lights

Hydrogen It’s own special group Doesn’t match the properties of the other alkali metals Wants to give away its only electron Most abundant element in universe Very reactive Fusion/fission