ELEMENTS ATOMS COMPOUNDS AND MOLECULES

By Patrick Pascua

What is an element

An element is a pure substance that cannot be broken down into any simpler substances by chemical methods. In that light, an element is the simplest kind of matter. We're used to calling them elements, but we also call them chemical elements, and this is because they are the basis for chemical combinations and chemical reactions.

What is an Atom

• An atom is the smallest amount of a substance that we can have.

• That will still retain all the features of that substance. Should it be subdivided any more.

• The qualities of the substance it was will be lost. The

• atom comes from an ancient Greek idea that essentially stated exactly that. Today we know that the "substance" spoken of here is a chemical element, and an atom of an element is the smallest unit into which we can divide that element.

Periodic tableThe periodic table of the chemical elements (also, periodic table of the elements or just periodic table) is a

tabular display of the chemical elements. Although precursors to this table exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869, who intended the table to illustrate recurring ("periodic") trends in the properties of the elements. The layout of the table has been refined and extended over time, as new elements have been discovered, and new theoretical models have been developed to explain chemical behaviour.

A molecule is defined as a sufficiently stable, electrically neutral group of at least two atoms in a definite arrangement held together by very strong (covalent) chemical bonds. Molecules are distinguished from polyatomic ions in this strict sense. In organic chemistry and biochemistry, the term molecule is used less strictly and also is applied to charged organic molecules and bimolecular.

MOLECULES

Compounds

• A chemical compound is a pure chemical substance consisting of two or more different chemical elements

• It can be separated into similar substances by chemical reactions and that have a unique and defined chemical structure.

Metals & Non-metals

• Metals have many properties like they are lustrous and are hard. They are also very good conductors of heat and electricity. They most time of the magnetic also.

• Non-metals also have many properties as well. Their properties are pretty much the opposite of metals.

Chemical Reactions

• A chemical reaction is a process that leads to the transformation of one set of chemical substances to another studied by chemists under a field of science called chemistry.

• It can be either spontaneous that is requiring no input of energy or non-spontaneous, that often comes about only after input of some form of energy, viz. heat, light or electricity. Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds.

Non-Chemical reactions

A non-chemical reaction is Butter melting, soap or detergent, an electric light bulb Steam forming in a teakettle, Hand lotion, removing gum (by freezing it) & air escaping from a balloon.

Identifying chemical reaction

Synthesis comes to us from Greek, by way of Latin, and literally means to "put together". A synthesis reaction is one in which elements or small compounds are combined to make a more complex compound. The simplest synthesis reactions are easy to recognize because they have only one product. (More complex synthesis reactions may have one large product along with a smaller product.)

Sample synthesis reactions could include:

2 Na + Cl2 -> 2 NaCl

SO2 + H2O -> H2SO3

CH2CH2 + HBr -> CH3CH2Br (this is an organic reaction, but still easy to recognize as synthesis)

Decomposition is roughly the opposite of synthesis it is a breaking down of one molecule into two (or more) smaller molecules or elements. These reactions are easy to recognize because they start with one relative large reactant and finish with multiple smaller products. Sometimes a catalyst, electricity, light or heat may be required to cause the decomposition, and they may be indicated in the reaction, either as a reactant or placed over the reaction arrow.

Sample decomposition reactions could include:

2 H2O + electricity -> 2 H2 + O2

Bibliography

Yahoo answersWikipediaHelium