The components and characteristics of the atom

In the environment there are currently several types of atoms 

Each atom is different from all other atoms

The atom is composed of two components 

I / core: and that is composed of two components which are called nucleons (The number Nucleon denoted A)

1/the protons: positively charged particles , its electric charge q_p called elementary charge is equal to

q_p= e = 1.6x10^-19C

The proton mass m_{p is very low. It is equal to}  
m_p=1,67x10^-27 Kg

Protons of all nuclei are identical, they are different from one atom to another by their number (Rated Z)

2/The neutrons: as its name suggests, the neutron is an uncharged particle
The mass of the neutron m_{n is close to that of the proton. It is equal to} m_n=1,67x10^-27Kg

(The number of neutrons rated N)

II / The electrons

The electron carries an electric charge q_e negative equal to the opposite of the elementary charge

Q_e= -e = -1,6x10^-19 C

The mass of an electron is extremely low and valleys 9,1x10^-31 Kg

It is 1836 times lower than that of the proton.

 
Electrons of all atoms are the same, they differ only by their number
In the basic state is the number of electrons equal to the number Z the number of protons contained in the core
 
Note: The mass of an electron is negligible
 
A ring containing Z proton electric charge equal to the sum of the charges of protons that compose it. Like all protons are identical and have the same elementary charge e then in charge of a nucleus containing Z protons is equal to:

Q_noyau =Zxe

The weight of a core consisting of Z protons and neutrons N is given by the relation:

M _noyau = Z.m_p + N m_p

As the masses of the proton and neutron are almost equal, then:

M _noyau=Zm_p+Nm_p=A.m_p=Ax1,67x10^-27 Kg

The electron mass is much smaller than that of the core can be considered as the mass of the atom is close to that do its core.

We therefore to m_atome =Ax1,67x10^-27 Kg  

The atomic molar mass is almost equal M=Ax1,67x10^-27 N ,where N is Avogadro's number as N=6,02x10²³ . As a result:

M=Ax1,67x10^-27x6,02x10²³ Kg =Ax10^-3 Kg = A.g

It is therefore seen that the mass number A is approximately equal to the value of the atomic molecular weight in grams
This is why A is called mass number

 

A rough picture of the atom

Definition of a chemical element:
 
Atoms and ions having the same charge number Z corresponding to the same chemical element
 
In a chemical reaction there is conservation of chemical elements
A chemical element characterized by its atomic number Z and a symbol
Definition of isotopes:
 
The isotopes of a chemical element are atoms whose nuclei have the same charge number Z and the mass number A different

 

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