Atoms and Ions

موضوع: Atoms and Ions الجمعة فبراير 27, 2009 9:01 am

:The atom

The atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of Hydrogen-1, which is the only stable isotope with no neutron). The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other, forming a molecule. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it has a positive or negative charge and is an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determines the isotope of the element.

The name atom comes from the Greek ἄτομος/átomos, α-τεμνω, which means uncuttable, something that cannot be divided further. The concept of an atom as an indivisible component of matter was first proposed by early Indian and Greek philosophers.

The ion:

An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge.
A negatively charged ion, which has more electrons than it has protons, is known as an anion (ἀνά ana: Greek 'up') (pronounced /ˈænaɪən/; an-eye-on). Conversely, a positively-charged ion, which has fewer electrons than protons, is known as a cation (κατά kata: Greek 'down') (pronounced /ˈkætaɪən/; cat-eye-on).

An ion consisting of a single atom is called a monatomic ion, but if it consists of two or more atoms, it is a polyatomic ion. Polyatomic ions containing oxygen, such as carbonate and sulfate, are called oxyanions.

Ions are denoted in the same way as electrically neutral atoms and molecules except for the presence of a superscript indicating the sign of the net electric charge and the number of electrons lost or gained, if more than one. For example: H+ and SO42−.

موضوع: رد: Atoms and Ions الأربعاء مارس 04, 2009 7:38 pm

thanks soso its great Embarassed

موضوع: رد: Atoms and Ions الأربعاء مارس 25, 2009 10:47 pm

U R welcome
Thnx Anstasia

موضوع: رد: Atoms and Ions الخميس أبريل 02, 2009 5:53 pm

thanks SARAH so much indeed