The Periodic Table

Introduction to the Periodic Table

By 1830 fifty-five different elements had been isolated and named.In 1869 Mendeleev arranged elements in order of increasing atomic mass and found that elements with similar properties fell into groups.Moseley improved the periodic table by arranging the elements according to atomic number instead of atomic mass.

Modern Periodic Table

Contains seven period or rows of elements whose properties change gradually and eighteen groups or columns, each with a family of elements having similar properties.

Organization of Periodic Table

Groups 1 and 2 along with groups 13 to 18 are called the representative elements.Groups 3 to 12 are called the transition elements.

Metal

Has lusterConducts heat and electricityIs malleable and ductile

Nonmetals

Are usually gases or brittle solids at room temperature

Metalloids

Shares properties with metals and nonmetals

Symbols

Are abbreviations usually based on the element’s name

Representative Elements

Groups 1 and 2 are active metals found in nature combined with other elementsAlthough hydrogen is placed in Group 1, it is not a metal and it shares properties with Groups 1 and 17

Alkali Metals

Silvery solids with low densities and low melting pointsThey increase in reactivity from top to bottom of the periodic table

Alkaline Earth Metals

Are denser, harderHave higher melting pointsAre slightly less active than alkali metals in the same period

Groups 13 through 18

May contain metals, nonmetals, or metalloids in solid, liquid, or gas form.The boron family elements in group 13 are all metals except boron, which is a metalloid; these elements are used in a variety of products.

Carbon Group

Elements are all metalloids or metals, except carbon itselfCarbon is found in all living things and exists in several forms.Silicon and germanium are used in electronics as semiconductors.Tin an lead are used in many products.

Nitrogen Group

Contains nitrogen and phosphorusWhich are required by living thingsWhich are used in industry

Oxygen Family

Contains oxygen and sulfurWhich are essential for lifeUsed to manufacture many products

Halogen Group

Elements from salts with sodium and with other alkali metals

Noble Gases

Rarely combine with other elementsThey are often used in lighting and inflating balloons.

Transition Elements

Groups 3 to 12 are metalsMost are combined with other elements in oresThe iron triad is composed of iron, cobalt, and nickelThey are used in many applicationsSeveral transition elements can be used as catalysts, substance that make a reaction occur faster.

Inner Transition Elements

Are called lanthanides and actinidesThe lanthanides are soft metals and were once thought to be rare.All the actinides are radioactive; several are synthetic elements that do not occur naturally.Dental materials are sometimes made of new composites, resins, and porcelains.

What does reactivity mean?9F Reactivity in chemistry

But an element might react very quickly with one chemical and hardly at all with another. So is it reactive or not?To compare the reactivity of different elements, we might see how easily they react with oxygen.

Some metals corrode in minutes out on the bench.

Others take longer to corrode, unless you heat them.

Elements that are reactive readily take part in reactions with other chemicals.

9F The Gold Cup again?

We can list metals in order of how quickly they react with oxygen.

This ranking of metals according to reactivity is called the reactivity series.

speed of reaction with oxygenleast reactive

most reactive

What if we react different metals with acid?

9F Reaction of metals with acid

copper – no bubbles, no reaction with acid magnesium – the metal reacts quickly with the acid,

producing lots of bubbles

iron – the metal reacts slowly, producing a few bubblessodium – the metal bursts into flames, a very strong reactionlead – the metal reacts very slowly, producing very few bubbles

9F What about water?

We can also rank metals by their reaction with water.

Compare with the reactivity series for oxygen and acid.

The reactivity series is very useful. How can we learn it?

reactivity series with

oxygen acid water

potassium

sodiummagnesiumzincironleadcoppergold

potassiumsodiummagnesiumzincironleadcoppergold

potassium

sodiummagnesiumzincironleadcoppergold

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Chapter 4 Properties and Changes of

Matter

Section 1 – Physical and Chemical Properties

Section 2 – Physical and Chemical Changes

Pages 104 - 129

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Physical Property

Characteristic that CAN be observed WITHOUT changing the composition of the substance.Appearance – properties detected by sensesState - can be liquid, solid, or gas

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Physical Property cont…

Volume, mass, and density – measurements that describe physical propertiesMelting point & boiling point are physical properties of a substanceBehavior – the way some substances behave

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Chemical Property

Characteristic that CANNOT be observed without altering the substanceAbility to burnTendency to rustReaction to other substances such as acids

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Physical Change

Form or appearance of matter changes, but composition stays the sameShape can change, but substance does notExample: Dissolving a solid into a liquidChanging states through vaporization, condensation, sublimation, or deposition does not change the composition of matter.

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Chemical Change

Results in a change in the substance’s compositionColor can changeOdor sometimes changesFormation of gas or precipitation of a solidEnergy is gained or released during a chemical changeChemical changes are NOT easily reversed.

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Big Difference

Chemical changes DO alter the composition of substancesPhysical changes DO NOT alter the composition of substances

Examples: water freezes or evaporates – amount of matter stays the same -> physical changeWood burns – ashes, smoke, and gases still total the same amount of matter -> chemical change.

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Law of Conservation of Mass

Particles of matter are not created or destroyed as the result of physical or chemical changes.