Concepts of chemistry


Chemistry is a branch of physical science that studies the composition, structure, properties and change of matter.

The following topic areas are the most basic concepts that a successful chemistry student needs to master:

 

  • Chemical Nomenclature.
  • Atomic Structure.
  • Periodic Table.
  • Lewis Structure.
  • Physical states of matter.
  • Chemical Reactions.
  • Acid-Base Chemistry.

CHEMICAL NOMENCLATURE:

A chemical nomenclature is a set of rules to generate systematic names for chemical compounds. The nomenclature used most frequently worldwide is the one created and developed by the International Union of Pure and Applied Chemistry (IUPAC).The primary function of chemical nomenclature is to ensure that a spoken or written chemical name leaves no ambiguity concerning which chemical compound the name refers to: each chemical name should refer to a single substance. A less important aim is to ensure that each substance has a single name, although a limited number of alternative names is acceptable in some cases.

ATOMIC STRUCTURE:

An atom is the smallest building block of matter. Atoms are made of neutrons, protons and electrons. The nucleus of an atom is extremely small in comparison to the atom. If an atom was the size of the Houston Astrodome, then its nucleus would be the size of a pea.

PERIODIC TABLE:

Scientists use the Periodic Table in order to find out important information about various elements. Created by Dmitri Mendeleev (1834-1907), the periodic table orders all known elements in accordance to their similarities. There are two main classifications in the periodic table, "groups" and "periods." Groups are the vertical columns that include elements with similar chemical and physical properties. Periods are the horizontal rows. Going from left to right on the periodic table, you will find metals, than metalloids, and finally nonmetals. The 4th, 5th, and 6th periods are called the transition metals. These elements are all metals and can be found pure in nature. They are known for their beauty and durability. The transition metals include two periods known as the lanthanides and the actinides, which are located at the very bottom of the periodic table. The chart below gives a brief description of each group in the periodic table.

LEWIS STRUCTURE:

Lewis diagrams, also called electron-dot diagrams, are used to represent paired and unpaired valence (outer shell) electrons in an atom. For example, the Lewis diagrams for hydrogen, helium, and carbon are:

where the symbol represents the element (in this case, hydrogen, helium, and carbon) and the dots represent the electrons in the outer shell (in this case, one, two, and four). The Lewis structure is used to represent the covalent bonding of a molecule or ion.

 

PHYSICAL STATES OF MATTER:

  • Solid, liquid, gas.

Physical state

Definite volume

Definite shape

Example

Solid

Yes

Yes

Book, pen

Liquid

Yes

No

Water, milk

Gas

No

No

CO2, Air

 

 

 

CHEMICAL REACTIONS:

A chemical reaction is a process in which the identity of at least one substance changes. A chemical equation represents the total chemical change that occurs in a chemical reaction using symbols and chemical formulas for the substances involved. Reactants are the substances that are changed and products are the substances that are produced in a chemical reaction.

The general format for writing a chemical equation is

reactant1 + reactant2 + … → product1 + product2 + …

 

ACID-BASE CHEMISTRY:

Acid-Base Reactions. When an acid and a base are placed together, they react to neutralize the acid and base properties, producing a salt. The H(+) cation of the acid combines with the OH(-) anion of the base to form water. The compound formed by the cation of the base and the anion of the acid is called a salt.

 

 

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