| |
|
|
|
| |
|
| |
|
|
|
| |
ATOMS:
An atom is the smallest particle comprising any element. An atom is composed of an electron cloud surrounding a dense nucleus. The nucleus consists of PROTONS (positively charged) and NEUTRONS (neutral). The electron cloud consists of the ELECTRONS (negatively charged). When the number of protons in the nucleus equals the number of electrons in the surrounding cloud, the atom becomes electrically neutral. Otherwise it is called an ion which has either positive or a negative charge on the whole. Any atom is classified on the basis of its protons and neutrons. The numbers of protons determine the atomic number and the numbers of neutrons determine the isotope of the element. The number of electrons determine the chemical properties of an element. The elemental symbols (shown in the periodic table) represent one atom of an |
|
| |
 |
|
| |
ELECTRON ORGANISATION AROUND
THE NUCLEUS:
All atoms like to have a stable configuration i.e. they tend to obtain eight electrons in heir last shell. The atoms do this by
• Gaining electrons
• Losing electrons
• Sharing electrons
The atoms with 1, 2, or 3 electrons in their last shell tend to lose their electrons (to the ones with 5, 6, or 7 electrons in their outer shell). The atoms that have 5, 6, or 7 electrons ion their last shell tend to gain electrons (from the ones with 1, 2, or 3 electrons in their outer shell). The atoms with 4 electrons in their outer shell tend neither to gain nor to lose their electrons, they tend to share them. |
|
| |
ATOMIC MASS:
Atomic mass is the mass of an atom at rest. It can be described as the sum total of the mass of protons, neutrons and electrons (protons + neutrons + electrons) at rest. It is expressed in ATOMIC MASS UNIT (unit- amu).
ATOMIC MASS UNIT: One atomic mass unit is defined as 1/12 the mass of a carbon-12 atom (which is equal to 1.66 X 10-24g). {1/12th 12C isotope of carbon = 1amu}.
ATOMIC WEIGHT: Atomic weight is the number which tells us how many times an atom of a particular element is heavier than an atom of Hydrogen (being the lightest it has been assigned the atomic no. 1).
ATOMIC NUMBER: Atomic number is the number of protons in the nucleus of an atom. MASS NUMBER: Mass number is the total number of protons + neutrons present in the nucleus of an atom.
Gram Atomic Mass = Mass Of Element in Grams
Atomic Mass Of Element |
|
| |
|
|
|