On Earth, matter usually can be found as a solid, liquid, or gas. What are elements?

On Earth, On Earth, mattermatter

usually can beusually can be

found as afound as a

solid,solid,

liquid,liquid,

or gas.or gas.

What are elements?What are elements?

Elements and the Atomic Elements and the Atomic StructureStructure

ElementsElements

All matter is made elements. All matter is made elements. An An elementelement is a substance that is a substance that

cannotcannot be broken down into simpler be broken down into simpler substancessubstances

by physical or chemical means.by physical or chemical means. Ninety-two elements occur Ninety-two elements occur

naturally on Earth and in the naturally on Earth and in the stars. stars.

Elements larger than 92 are man-made and radioactive.

Elements are Made of AtomsElements are Made of Atoms

Each element has distinct Each element has distinct characteristics. characteristics.

An An atomatom is the smallest particle of an is the smallest particle of an element that has all of the element that has all of the characteristics of that element.characteristics of that element.

Elements are Made of AtomsElements are Made of Atoms

The The nucleusnucleus, which is made, which is madeup of protons and neutrons,up of protons and neutrons,forms the center of an atom. forms the center of an atom.

– A A proton (pproton (p++)) is a tiny particle that has mass and is a tiny particle that has mass and a positive electrical charge. a positive electrical charge.

– A A neutron (nneutron (n00)) is a particle with about is a particle with about the same mass as a proton, but it has no the same mass as a proton, but it has no electrical charge.electrical charge.

All atomic nuclei have a positive All atomic nuclei have a positive charge.charge.

Elements are Made of AtomsElements are Made of Atoms

The number of protonsThe number of protonsand neutrons in differentand neutrons in differentatoms varies widely. atoms varies widely.

The The atomic numberatomic number is the number of is the number of protons in an atom’s nucleus. protons in an atom’s nucleus.

The The mass number or atomic massmass number or atomic mass is is the combined number of protons and the combined number of protons and neutrons, which are in the nucleus.neutrons, which are in the nucleus.

An An electron (eelectron (e––)) has little mass, but it has little mass, but it has a negative electrical charge.has a negative electrical charge.

Elements are Made of AtomsElements are Made of Atoms

Surrounding the nucleus of an atom are Surrounding the nucleus of an atom are smaller particles called electrons.smaller particles called electrons.

An atom has an equal number of An atom has an equal number of protons and electrons which produces protons and electrons which produces an atoman atom

that has no overall charge. that has no overall charge.

Elements are Made of AtomsElements are Made of Atoms An An energy levelenergy level represents the area represents the area

in an atom where an electron is most in an atom where an electron is most likely to be found. likely to be found.

Electrons in Energy LevelsElectrons in Energy Levels

The number of electrons in the outermost The number of electrons in the outermost energy level determines the chemical energy level determines the chemical behavior of the different elements. behavior of the different elements.

Valence electronsValence electrons are the outermost are the outermost electrons in an atom. electrons in an atom.

Elements with the same number of valence Elements with the same number of valence electrons have similar chemical properties.electrons have similar chemical properties.

Group 1 has 1 valence electron, group 2 Group 1 has 1 valence electron, group 2 has 2,has 2,

13 has 3, 14 / 4, 15 / 5, 16 / 6, 17 / 7, 18 / 13 has 3, 14 / 4, 15 / 5, 16 / 6, 17 / 7, 18 / 8. 8.

IsotopesIsotopes The number of neutrons in the nuclei of The number of neutrons in the nuclei of

an element’s atoms can vary. an element’s atoms can vary.

IsotopesIsotopes are atoms are atoms of the same element of the same element that have different that have different mass numbers and mass numbers and the same chemical the same chemical properties.properties.

Almost all atoms have isotopes

What Elements are Most What Elements are Most Abundant?Abundant?

CompoundsCompounds

A A compoundcompound is a substance that is is a substance that iscomposed of atoms of two or morecomposed of atoms of two or moredifferent elements that are chemicallydifferent elements that are chemicallycombined.combined.

Most compounds have totally different Most compounds have totally different properties from the elements of which properties from the elements of which they are composed. they are composed.

Chemical bondsChemical bonds are the forces that are the forces that hold the elements together in a hold the elements together in a compound creating a state of stability.compound creating a state of stability.

IonsIonsIonic BondsIonic Bonds

– Positive and negative ions attract each other. Positive and negative ions attract each other. – An An ionic bondionic bond is the attractive force between two ions is the attractive force between two ions

of opposite charge. of opposite charge.

Ionic BondingIonic Bonding

Ions TravelIons Travel Group 1 travels to group 17Group 1 travels to group 17 Group 2 travels to group 16Group 2 travels to group 16

Metals and non metals attractMetals and non metals attract All compounds are looking to become All compounds are looking to become

stable with 8 valence electrons.stable with 8 valence electrons.

Properties of ionic bondingProperties of ionic bonding BrittlenessBrittleness High melting pointsHigh melting points Good electrical conductivityGood electrical conductivity

CompoundsCompounds

Covalent BondsCovalent Bonds

– A A covalent bondcovalent bond is the attraction of two is the attraction of two atoms for a atoms for a sharedshared pair of electrons that pair of electrons that holds the atoms together. holds the atoms together.

CompoundsCompounds

– A A moleculemolecule is composed of two or more is composed of two or more atoms held atoms held togethertogether by by covalent bonds.covalent bonds.

Covalent BondingCovalent Bonding

Formed when non-metal atoms share Formed when non-metal atoms share valence electronsvalence electrons

7 + 7 =16 7 + 7 =16 6 + 6 =16 6 + 6 =16

Use a dot diagram to predict how an atom Use a dot diagram to predict how an atom willwill

share it’s valence electrons.share it’s valence electrons.

Mixtures and SolutionsMixtures and Solutions A mixture is a combinationA mixture is a combination

of two or more components thatof two or more components thatare NOT chemically combined,are NOT chemically combined,and retain their identities. and retain their identities.

Mixtures can be physically separated. The identities of the substances DO NOT change.

A homogeneous mixture is also called a

solution.

MixturesMixtures When a mixture’s components are When a mixture’s components are

easily recognizable, such as pizza, it easily recognizable, such as pizza, it is called a is called a heterogeneousheterogeneous mixture. mixture.

• In a homogeneous mixture such

as chocolate milk, the component particles cannot be distinguished,

even though they still retain their

original properties.

MixturesMixtures Common Techniques for Separating MixturesCommon Techniques for Separating Mixtures

Distillation – separates a mixture based on boiling points of the component.

Examples :saltwatercrude oil into gasoline and kerosene

Magnet – separates iron from other objects.

Centrifuge – spins and separates according to densities.

SolutionsSolutions A mixture that appears to be a single A mixture that appears to be a single

substance but is composed of substance but is composed of particles of two or more substances particles of two or more substances that are distributed evenly amongst that are distributed evenly amongst each other.each other.

A solution may be liquid, gaseous, or solid.Examples of solutions

Liquid - seawaterGas - airSolid - alloys

SolutionsSolutions DissolvingDissolving – – The process in whichThe process in which

particles of substances separate andparticles of substances separate and

spread evenly amongst each other.spread evenly amongst each other.• Solute – substance that is dissolved. A solute is

soluble, or able to dissolve. • A substance that is insoluble is unable to dissolve, forms a mixture that is not homogeneous, and therefore NOT a solution.

• Solvent – substance in which solute is dissolved.

SolubilitySolubility

The The solubilitysolubility of a solute is the amount of solute of a solute is the amount of solute needed to make a saturated solution using a needed to make a saturated solution using a given amount of solvent at a certain temperature.given amount of solvent at a certain temperature.

SolubilitySolubility is usually expressed in grams of solute is usually expressed in grams of solute per 100 ml of solvent (g/100ml)per 100 ml of solvent (g/100ml)

Three (3) methods that affect solubilityThree (3) methods that affect solubility Mixing, stirring, or shakingMixing, stirring, or shaking HeatingHeating Crushing or grindingCrushing or grinding

SuspensionSuspension

A mixture in which particles ofA mixture in which particles ofa material are dispersed through-a material are dispersed through-out a liquid or gas but are largeout a liquid or gas but are largeenough that they settle out.enough that they settle out.

Particles are insoluble, so they DO NOT Particles are insoluble, so they DO NOT dissolve in the liquid or gas.dissolve in the liquid or gas.

Particles can be separated using a filter.Particles can be separated using a filter. Examples:Examples: Salad dressingSalad dressing Medicines that sayMedicines that say““shake well before use” shake well before use”

ColloidsColloids

A mixture in which the particles are A mixture in which the particles are dispersed throughout but are not dispersed throughout but are not heavy enough to settle out.heavy enough to settle out.

Made up of solids, liquids and gases.Made up of solids, liquids and gases. Examples :Examples :

MayonnaiseMayonnaise Stick deodorantStick deodorant milkmilk