STRUCTURE OF ATOM

STRUCTURE OF ATOM

ATOM

                       - smallest unit of matter
                                   that retains the properties and characteristics of the element.

                       - each element is made up of atoms

                       - atoms are extremely small.


 Smallest atom- hydrogen atoms

                      - diameter = less than 0.1 nanometer .

COMPOSITION OF AN ATOM

Individual atoms are composed of different subatomic particles

3 types of subatomic particles important for understanding chemical reactions in human body

1.PROTONS
2. NEUTRONS
3. ELECTRONS

NUCLEUS

            The dense central core of an atom

PROTONS  p+

                 - With in the nucleus

                 - positively charged particles


NEUTRONS  n0

               - with in nucleus

               - neutral or uncharged

ELECTRONS  e-

                - tiny

                - negatively charged

                - move about in space surrounding nucleus


ELECTRON CLOUD MODEL

electrons do not follow a fixed path or orbit

form a negatively charged cloud that envelops the nucleus.


ELECTRON SHELL MODEL

ELECTRON SHELLS  are certain regions around the nucleus with in which specific group of electrons are most likely to move about 

simple circles around the nucleus.


ELECTRON ARRANGEMENT

Maximum electrons first electron shell can hold is 2
Maximum electrons second electron shell can hold is 8
Maximum electrons third electron shell can hold is 18

eg. 
1. sodium- 11

first shell- 2
second shell- 8
third shell- 1


2. iodine- 53

first shell- 2
second shell- 8
third shell- 18
fourth shell- 18
fifth shell- 7 

The most massive element present in the human body is iodine which has a total of 53 electrons.


CHARGE OF AN ATOM

The number of electrons in an atom = number of protons .

An electron carries one negative charge.

A proton carries a positive charge.

They balance each other 

THUS each atom is electrically neutral

Its total charge is zero.