ElementsAn element is a pure An element is a pure

substance that cannot be substance that cannot be separated into simpler separated into simpler substances by physical or substances by physical or chemical meanschemical means

A pure substance is a A pure substance is a substance in which there is substance in which there is only one type of particleonly one type of particle

Because elements are pure Because elements are pure substances, each element contains substances, each element contains only one type of particleonly one type of particle

For example, every particle in a 5 For example, every particle in a 5 gram nugget of the element gold is gram nugget of the element gold is like every other particle of goldlike every other particle of gold

The particles of a pure substance are The particles of a pure substance are alike no matter where that substance alike no matter where that substance is found.is found.

Although a meteorite might travel Although a meteorite might travel more than 248 million miles to reach more than 248 million miles to reach Earth, the particles of iron in a Earth, the particles of iron in a meteorite are identical to the particles meteorite are identical to the particles of iron in objects around your home.of iron in objects around your home.

Every element has a unique set of

properties Each element has a unique set of Each element has a unique set of properties that allows you to properties that allows you to identify itidentify it

This unique properties are called This unique properties are called characteristic propertiescharacteristic properties

Some characteristic properties Some characteristic properties are physical propertiesare physical properties– Boiling pointBoiling point– Melting pointMelting point– DensityDensity

Some of these characteristic Some of these characteristic properties are chemical propertiesproperties are chemical properties– FlammabilityFlammability– Reactivity with acidReactivity with acid– Reactivity with waterReactivity with water

For example, helium and krypton are For example, helium and krypton are unreactive gasesunreactive gases

Comparing the density of helium and Comparing the density of helium and krypton demonstrates their unique krypton demonstrates their unique characteristic propertiescharacteristic properties– Helium is less dense than air so a Helium is less dense than air so a

balloon filled with helium will float balloon filled with helium will float upup

– Krypton is more dense than air so a Krypton is more dense than air so a krypton filled balloon will sink to the krypton filled balloon will sink to the groundground

Identifying elements by their properties Comparing cobalt, iron and nickel you Comparing cobalt, iron and nickel you

might consider:might consider:– Melting pointMelting point– DensityDensity– Conduct electricityConduct electricity– React with oxygenReact with oxygen

Other properties might be Other properties might be – ColorColor– HardnessHardness– TextureTexture– Flammability (ex: hydrogen and carbon)Flammability (ex: hydrogen and carbon)– React with water (ex: sodium and lithium)React with water (ex: sodium and lithium)– React with acid (ex: zinc)React with acid (ex: zinc)

Elements are classified by their properties

Elements are classified into groups Elements are classified into groups according to their shared properties.according to their shared properties.

For example, cobalt, nickel, and For example, cobalt, nickel, and cobaltcobalt– All three are shiny, and all three All three are shiny, and all three conduct thermal energy and conduct thermal energy and electric currentelectric current

Scientists have grouped these three Scientists have grouped these three elements, along with other similar elements, along with other similar elements, into one large group called elements, into one large group called metalsmetals

Metals are not all exactly alike, but Metals are not all exactly alike, but they do have some properties in they do have some properties in commoncommon

If you know the category---you

know the properties

It is shiny, hard, malleable and It is shiny, hard, malleable and conducts electricity-----it must be conducts electricity-----it must be

a METAL!!a METAL!!

3 Categories of Elements MetalsMetals

– Shiny, good conductors of thermal Shiny, good conductors of thermal energy,and electrical current, malleable energy,and electrical current, malleable and ductileand ductile

NonmetalsNonmetals– Dull, poor conductors of thermal energy Dull, poor conductors of thermal energy

and electric current, brittle and and electric current, brittle and unmalleableunmalleable

Metalloids (semiconductors)Metalloids (semiconductors)– Have properties of both metal and Have properties of both metal and

nonmetalsnonmetals– Some or shiny, they are somewhat Some or shiny, they are somewhat

malleable and ductile. Some conduct malleable and ductile. Some conduct thermal energy and electric currentthermal energy and electric current

Examples of Metals:Examples of Metals:–Iron, cobalt, nickel, Iron, cobalt, nickel, aluminum, magnesium, aluminum, magnesium, calcium, zinc, chromium, calcium, zinc, chromium, copper, silver, gold, mercurycopper, silver, gold, mercury

Examples of Nonmetals:Examples of Nonmetals:–Carbon, nitrogen, oxygen, Carbon, nitrogen, oxygen, sulfur, chlorine, argon, neon, sulfur, chlorine, argon, neon, helium, hydrogen, radon, helium, hydrogen, radon, kryptonkrypton

All of the MetalloidsAll of the Metalloids–Boron, silicon, germanium, Boron, silicon, germanium, arsenic, antimony, telluriumarsenic, antimony, tellurium

Elements are displayed in a Elements are displayed in a Periodic Chart of ElementsPeriodic Chart of Elements

Elements in the periodic chart are Elements in the periodic chart are assigned a symbolassigned a symbol

A symbol is a short hand way of A symbol is a short hand way of identifying the elementidentifying the element

Examples of element symbols are:Examples of element symbols are:– H for hydrogen, C for carbonH for hydrogen, C for carbon

Some symbols have two letters:Some symbols have two letters:– He for helium, Co for cobaltHe for helium, Co for cobalt

Some symbols derive from other Some symbols derive from other languages:languages:– Fe for iron, Au for gold, Ag for Fe for iron, Au for gold, Ag for silversilver

Periodic Table of Elements

Black is solid blue is liquid purple is gas

Symbols are in different colors to indicate state of matter