228It’s elementary
An element is a pure substance that cannot
be broken down into simpler chemicals. An
element is made of only one type of atom.
So, the element hydrogen is made only of
hydrogen atoms, and gold of gold atoms.
Scientists recognize 117
different elements, which
have been organized into
a chart known as the
Periodic Table. This table
was first devised in 1869
by Russian chemist Dmitry
Mendeleyev, who organized
elements with similar
properties into groups.
The elements are arranged
by the size of their atoms.THE PERIODIC TABLE
Every element has a one- or two-letter
symbol. For example, Kr is the
symbol for the element Krypton.
Scientists use these symbols to write
down the chemical formulas for
molecules and chemical reactions.Metals are on
the left-hand
side and center
of the Periodic
Table. On the
right-hand side
are gases and
nonmetal solids.WHERE DO ELEMENTS COME FROM?
Most scientists believe that much of the hydrogen and
some of the helium in the universe were formed in the
“Big Bang” that formed the universe. Hydrogen
has the smallest and simplest atoms, and
helium has the next smallest.RADIOACTIVE DECAY
Some elements are made of atoms so
large they break apart spontaneously.
This is called radioactive decay, and
the subatomic particles (smaller than
atoms) and energy released by it can
be dangerous. Each radioactive
element has a half life, the time it takes
for half of its atoms to break apart.SCIENCE
Compounds
Most chemicals are
not pure elements, but
compounds. A compound
is a chemical made up of
two or more different
elements chemically
combined.Water is a
compound made
of two hydrogen
atoms and one
oxygen atom.HYDROGENLITHIUMSODIUM MAGNESIUMCALCIUM TITANIUMBORONAluminumCARBON NITROGEN FLUORINESulfUR CHLORINE ARGONOXYGENSCANDIUMSILICONPOTASSIUMPHOSPHORUSNEONVANADIUM CHROMIUM IRON COBALTHLi BeNa MgK Ca Sc Ti V CoArFS ClNC OSiBAl19 20 21 22 23 24 26 2711 123 41567891013 14 16 17 18NeFePCr15
Mn
MANGANESE 25RUBIDIUMCesiumFRANCIUMSTRONTIUMBARIUMRADIUMYTTRIUMACTINIDES or RARE-EARTH
RADIOACTIVE METALSZIRCONIUM NIOBIUM MOLYBDENUMTECHNETIUM RUTHENIUM RHODIUMHAFNIUM TANTALUMDUBNIUMTUNGSTEN RHENIUM OSMIUM IRIDIUMSEABORGIUM BOHRIUM HASSIUM MEITNERIUMPALLADIUM SILVER CADMIUM INDIUMPLATINUM GOLDROENTGENIUMTHALLIUMTIN ANTIMONY TELLURIUMRb Sr Y Zr Nb Mo Tc Ru RhHf Ta Re OsRf Db Sg Bh HsCsFr RaIn Sb TeTlAg CdAuRgPdPtDsIrMt40 41 42 43 44 45 IODINE XENONI Xe
37 38 3955 56 57—71 72 73 74 75 76 7787 88 89—103 104 105 106 107 108 1097846 47 48 49 51 52 53 54815079 80110 111LEAD BISMUTH POLONIUMPb Bi Po
ASTATINE RADONRnAt
82 83 84 85 86Ba or RARE-EARTH LANTHANIDES W HgSnNICKELNi
28 COPPERCu
29 ZINCZn
30 GALLIUMGa
31 GERMANIUMGe
32 ARSENICAs
33 SELENIUMSe
34 BROMINEBr
35 KRYPTONKr
36LANTHANUMACTINIUMCERIUM PRASEODYMIUMNEODYMIUMTHORIUM PROTACTINIUM URANIUM NEPTUNIUMPROMETHIUM EUROPIUM TERBIUM DYSPROSIUM HOLMIUM ERBIUM THULIUM YTTERBIUMAMERICIUM CURIUM BERKELIUM EINSTEINIUM FERMIUMMENDELEVIUMNOBELIUMLa Ce Pr NdAc Th Pa U NpEu Gd TbBkDy Ho Er Tm YbCf Es Fm Md No57 58 59 60 6189 90 91 92 93 PLUTONIUMSAMARIUMSmPu6294 LAWRENCIUMLUTETIUMLrLu
63 64 65 66 67 68 69 70 7195 96 97 98 99 100 101 102 103PmAm CmSymbolName
36Kr
Atomic
numberHELIUM 2HeBERYLLIUMMERCURY