Chemistry

Contents!• Elements and Atoms• What makes up an Atom • Atomic Numbers• Compounds (Ionic and Covalent) • Metals and Non Metals• The Periodic Table; What it is and who discovered it?

• Chemical Reactions• Identifying Chemical Reactions• Chemical and Physical changes• Reaction rate and factors affecting it• Bibliography

By Catherine

Elements and Atoms

Atoms

What Are Atoms• An atom is something that makes up something else.

• Each object living or non living is somehow made up of atoms

• An atom cannot be seen by the human eye unless with help of a very powerful microscope.

• Atoms make up elements which then make up matter.

The Structure Of An AtomAtoms are made up from Electrons,

Protons and Neutrons

The centre of an atom is called the nucleus, the nucleus is basically a collection of protons and neutrons.

Protons are positively charged particles and neutrons are evenly charged particles.

Around the nucleus are the particles called electrons. These electrons are negatively charged and spin around the nucleus at amazingly fast speeds.

Neutrons have no charge and Are stationary in the nucleus

The protons and neutrons

Electrons

Protons

Neutrons

Electrons

What makes up an atom?

• Protons are an element of an atom and can be particles of importance and used by themselves.

• Protons have actually been known to become neutrons from certain experiments and studies.

• Protons are a similar size to neutrons but are much bigger then electrons.

Protons

Neutrons• Neutrons are found in almost every atom and have no electric charge.

• The hydrogen atom’s nucleus is the only one without neutrons.

• There is a minimum of one neutron in every other atom’s nucleus.

• The existence of neutrons were first discovered by physicist James Chadwick.

Electrons

• Electrons are the negatively charged particles which make up an atom.

• Electrons are so fast that it is impossible, even with today’s modern technology to tell where they are at any specific time.

• Electrons are very important in the world of electricity.

ElementsElements are things made up by atoms . Hydrogen is an element, oxygen is an element.

Nearly all of the elements have a place on the periodic table.

Elements cannot be made any smaller by any ordinary chemical method.

Elements are the building blocks of life, from elements come compounds.

Atomic NumbersEvery element has an atomic number.

This atomic number represents the number of protons in the substance.

Any element with an atomic number of 83 – 94 are thought to be unstable since they have no stable nuclei but still exist on earth.

** Nuclear substances are made up from these unstable elements.

CompoundsCompounds are two or more elements bounded together to make a new substance. There are 2 main types of bonds/comounds that can occur. One is the Covalent Compound the other the Ionic Compound.

Covalent CompoundsCovalent Compounds are compounds which when bonded

together share electrons. Covalent Compounds usually occur when two non metals are joined together. There area few main factors which can usually be used to distinguish Covalent Compounds from Ionic Compounds:

1. Covalent compounds usually have a lower boiling point to Ionic compounds

2. Covalent compounds are usually much more flammable then Ionic compounds

3. Covalent compounds don’t conduct electricity in water

Ionic Compounds

Ionic Compounds are usually made when a non metal and a metal are bonded together. Ionic compounds are where two or more ions are joined together by a strong electrical attraction. One of the ions has a positive charge the other a negative charge. The positive charge and the negative charged are attracted to each other by the same thing that makes the north and south poles of a magnet join together. Some main characteristics of Ionic compounds are:

• Ionic compounds have high melting and boiling points• Ionic compounds are very brittle and hard• Ionic compounds conduct electricity when they

dissolve in water

Metals and Non MetalsNon Metals: An element not having the character of a metal, as carbon or nitrogen

Metals: Any of a class of elementary substances, as gold, silver, or copper, all of which are crystalline when solid and many of which are characterized by opacity, ductility, conductivity, and a unique luster when freshly fractured.

Chemical Properties*Generalization

Metals Non Metals

Usually have 1-3 electrons in their outer shell

Usually have 4-8 electrons in their outer shell

Lose their valance electrons easily

Gain/share valance electrons easily

Form oxides that are basic Form oxides that are acidic

Are good reducing agents Are good oxidizing agents

Have lower electro-negativities

Have higher electro negativities

Physical Properties

*Generalization

Metals Non Metals

Good heat and electricity conductors

Poor electricity and heat conductors

Malleable- Can be beaten into thin sheets

Brittle- If solid

Ductile- Can be stretched into thin sheets

Nonductile

Possess Metallic luster Transparent as thin sheet

Solids at room temperature Solids, Liquids or Gases at room temp.

The Periodic TableThe Periodic Table has developed over many years to become the comprehensive table of elements it is today. It is used to name elements and the atomic value of each of them. So let’s investigate further…..

The Periodic Table

Periodic Table Key

The Discoverers of the Periodic Table

Arsitotle- 330BCAntoine Lavoisier- 1770 to 1789Jons Jakob Berzelius- 1828Johann Dobereiner-1829John Newlands-1864Lothar Meyer-1869Dmitiri Mendeleev-1869William Ramsay-1894Henry Moseley-1914Glen Seaborg-1940

A lot of historical events have occurred over time to make the periodic table the extensive table it is today. The first discoverer to have come up with theory of elements is believed to be Aristotle in the BC time period. He came up with the theory of 4 elements, earth, wind, fire and water.

Aristotle

Antoine Lavoisier

Antoine wrote the first extensive list of elements which contained 33 elements, he also distinguished metals from non metals. Later though, some of his ‘elements’ were later described as compounds and mixtures.

Jons Jakob Berzelius

Jons Jakob Berzelius was a Swedish chemist who is credited with the discovery of the elements, silicon, selenium, thorium and cerium.

Johann Wolfgang Dobereiner

Johann Doberiener discovered the trends of a certain group of elements. For example Johann discovered that the atomic mass of lithium and potassium was close to the atomic mass of sodium. Johann’s discoveries have been very helpful in the continued research and development of atomic numbers throughout science and chemistry.

John Alexander Reina Newlands

John was the first person to create a periodic table of elements in order of their atomic weight. Also his research predicted the existence of more elements including geranium.

Julius Lothar Meyer & Dmitri Mendeleev

Julius Lothar Meyer and Dmitri Mendeleev never worked together but are often thought the co- creators of the periodic table we know today after both continued to develop the theory of John Newlands that when elements are put in order on the periodic table elements with similar properties fall into a similar group. They both later published separate yet nearly identical periodic tables which included corrected atomic numbers and predicted new elements. Dmitri Mendeleev is still often given more credit of the discovery since he managed to predict 8 new elements and where they would be placed on the periodic table.

William Ramsay

William Ramsay was the discoverer of the Noble gases. Ramsay discovered a large component of air that was thought not to have any chemical reactivity and was unknown. Later on Ramsay discovered other gases such as, neon, krypton and xenon. He also received a Nobel Prize recognizing his work in 1904.

Henry Moseley

Henry showed the world that atomic numbers were not just random approximations instead he showed that atomic numbers actually had substantial basis. Moseley’s law provided support on the existence of atoms where an atomic number represented the number of protons in the atomic nucleus. His death occurred while fighting in the war which provoked a new law in Britain in which scientists couldn’t enlist for combat.

Glen SeaborgGlen Seaborg was the co discoverer of 10 elements• Plutonium• Americium • Curium• Berkelium• Californium• Einsteinium• Fermium• Mendelevium• NobeliumAnd another element, element 106 named seaborgium in his honor while he was alive. His discoveries also helped in curing diseases. He also shared a Nobel Prize with Edwin Mc Millian.

Chemical Reactions

A chemical reaction is when two or more elements react together in a particular way. There are generally five types of chemical reactions.

• Synthesis reactions • Decomposition reactions• Combustion reactions• Single Displacement • Double displacement

Synthesis Reactions

A synthesis reaction is when two or more simple compounds to form a more complicated one.

Decomposition Reactions A decomposition reaction is the complete opposite of

a synthesis reaction in the form that when something decomposition it goes from a complex molecule breaks down to something smaller and similar.

Combustion Reactions

A combustion reaction is when oxygen combines with another compound to form water and carbon dioxide. These reactions are exothermic, meaning they produce heat.

Single Displacement & Double Displacement

Single Displacement is when one element trades places with another element in a compound.

Double Displacement is when positive and negative charges switch places in two different molecules forming an entirely different compounds.

Identifying what reaction has occurred

When trying to figure out what chemical reaction is occurring during an experiment some things to think about are:

If your reaction has oxygen as one of it’s reactants and carbon dioxide and water as the product, a combustion reaction is occurring.

If the reaction has two or more chemicals mixing together to form one chemical it’s a synthesis reaction.

If a reaction has one large molecule re forming to make multiple small ones it’s a synthesis reaction.

If your reaction has any molecules that contain only one element it’s a single displacement reaction.

Identifying Chemical Reactions

Identifying that even a chemical reaction has occurred is the first step before you decided what reaction has occurred. Some ways to identify reactions are the physical changes. Boiling water to vapor is one of the easiest to understand. Obviously a chemical reaction has occurred since one substance has changed to another. Some other ways to identify chemical reactions occurring are:

• Changes in temperature• Changes in color• Bubbling

Irreversible and Reversible Chemical

Reactions Some chemical reactions are reversible and others aren’t.

Irreversible reactions include that of wood into ash, ash cannot be simply turned back into wood, there for this chemical reaction is irreversible.

Unlike ice to water which can be reversible since ice can melt to water but then water can be frozen again to turn back into ice.

Reaction RateThe rate of which a chemical reaction occurs is the speed in which the reactants are converted to products. It is thought that in order to react the particles of the reactants must collide and the faster that they collide will speed up the reaction progress.

Key Factors That Influence Reaction

RateTemperature: the hotter the temperature the kinetic energy of the particles increases which results in more collisions making the reaction progress faster

Size: The smaller the particles to chances of collision increase so the reaction rate increases

Stirring: Quickly stirring makes the particles move more which increases the chances of collision making the process faster

Bibliography

www.vtaide.com.auwww.wikkipedia.comwww.historyoftheuniverse.comwww.ausetute.com.au/pthistor.htmlwww.googleimages.comwww.chemhistory.comhttp://misterguch.brinkster.net/covalentcompounds.htmlwww.visionlearning.comhttp://www.answers.com/topic/chemical-reaction.com