The Periodic Table

Introduction to the Periodic Table By 1830, there were 55 different elements, used for many different things Today, there are 118 identified elements with more to come! 2

Dmitri Mendeleev Arranged elements in order of increasing atomic mass 3

Mendeleev’s table created in 1869 Mendeleev noticed that elements with similar properties fell into groups on the periodic table 4

Fun Fact! In his final version of the periodic table in 1871, Mendeleev left gaps, predicting they would be filled by elements not yet known to scientists. He correctly predicted the properties of these elements

Henry Moseley Moseley realized that some of the elements were out of order, so he rearranged the elements according to their atomic number 6

Today’s periodic table Elements are organized according to their atomic number Periods – a row of elements in the periodic table whose properties change gradually and predictably

Today’s periodic table Group or Family – a column of elements that have similar physical or chemical properties 7

Zones on the Periodic Table Representative elements – Groups 1-2 and groups 13-18 Transition elements – Groups 3-12 9

Metals Solids Luster Good conductor of heat and electricity Malleable Ductile 10

Nonmetals Usually gases or brittle solids Poor conductors of heat and electricity phosphorous sulfur

Metalloids Have some properties of metals and some of nonmetals arsenic boron 12

Element Symbols The symbol for an element must always be written with the first letter capitalized and the second or third as a lower case letter! Cu Cs

Alkali Metals Group 1 elements – Lithium, sodium, potassium, rubidium, cesium and francium Silvery solids with low densities and low melting points Very reactive elements – from top to bottom of the periodic table rubidium

Alkaline Earth Metals Group 2 elements – beryllium, magnesium calcium, strontium, barium, radium Denser, harder and have a higher melting point than alkali element in same period strontium 15

Boron Family Group 13 – all metals except Boron which is a metalloid Uses: B – cookware Al – cookware, popcans Ga –computer chips Indium wire 16

Carbon Family Group 14 carbon – nonmetal silicon & germanium - metalloids tin & lead - metals carbon germanium

The Nitrogen Family Group 15 includes nitrogen and phosphorous (nonmetals) Arsenic and antimony (metalloids) Bismuth (metal) antimony

fun fact Nitrogen is relatively unreactive. Sometimes it is used inside a sealed case to protect valuable documents that might react with oxygen or other gases in air

The Oxygen Family Group 16 includes Oxygen, sulfur, selenium (nonmetals) Tellurium, polonium (metalloids)

The Halogen Family Group 17 Includes Fluorine, chlorine, bromine, iodine (nonmetals) Astatine (metalloid) Chlorine gas

Noble Gases Group 18 Includes Helium, neon, argon, krypton, xenon, radon (nonmetals) This group is very stable

Transition Elements

Iron Triad Includes: iron, cobalt, and nickel All have magnetic properties cobalt iron 24

fun fact Molecules containing transition elements are important to the life processes of many organisms. Perhaps the most familiar example of this is found in the iron-containing heme complex of hemoglobin, which is responsible for the transport of oxygen in the blood of all vertebrates and some invertebrates

Transition element vocabulary Catalyst – a substance that can make something happen faster but is not changed itself Synthetic elements – man-made elements

Inner Transition Elements 2 groups: lanthanide series – from cerium to lutetium (numbers 58 – 71) actinide series – from thorium to lawrencium (numbers 90 - 103)

The Lanthanides Characteristics – soft metals thulium terbium

The Actinide Series Characteristics – radioactive, synthetic elements, metals uranium