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Ahmed saied Thu 11 Nov 2010, 5:01 amThe atom is the fundamental building unit of matter.
- It is the smallest building unit of matter that takes part in chemical reactions without being changed.
Atom consists of:
1- Nucleus (contain protons positively charged and neutrons of neutral charge).
2- Energy levels (contain electrons of negative charges).
* Electrons orbit the nucleus inside energy levels with very high speed, so we can't determine exactly the position of electron.
The path of electron around the nucleus is called orbital.
* If the atom gain amount of energy it is called exited atom the electron gain amount of energy called quantum, then they transfer to higher energy level and when they lose energy they return to lower level.
* Each energy level is saturated with specific number of electrons can be calculated from the relation (2n2).
- First level = 2 electrons
- Second level = 8 electrons
- Third level = 18 electrons
- Fourth level = 32 electrons
* The elements are known by their symbols (Latin letters) if the element symbols is one letter it must be written capital.
Ex: Hydrogen (H) oxygen (O) nitrogen (N).
* If the element symbol is two letters is must be written first is capital the second is small.
Ex: sodium (Na) calcium (Ca) neon (Ne).
- Atomic no.: the number of protons or electrons.
- Atomic no: = no of protons = no. of electrons.
- Mass no.: sum of protons and neutrons.
- No. of neutrons = mass no. - atomic no.
- Ex: For the following elements find mass, atomic number.
Protons, electrons and neutrons.
Electronic Configuration
We distribute electrons inside energy levels in sequence according to the atomic numbers.
Note:
In levels after the second we don't put more than eight electrons because this makes the atom more stable.
Elements can be divided into:
1- Active elements: have incomplete energy levels (form compounds with other elements).
2- In active elements: have complete energy levels (don't form compounds with other elements).
The inactive elements are called noble gases (inert gases)
- It is the smallest building unit of matter that takes part in chemical reactions without being changed.
Atom consists of:
1- Nucleus (contain protons positively charged and neutrons of neutral charge).
2- Energy levels (contain electrons of negative charges).
* Electrons orbit the nucleus inside energy levels with very high speed, so we can't determine exactly the position of electron.
The path of electron around the nucleus is called orbital.
* If the atom gain amount of energy it is called exited atom the electron gain amount of energy called quantum, then they transfer to higher energy level and when they lose energy they return to lower level.
* Each energy level is saturated with specific number of electrons can be calculated from the relation (2n2).
- First level = 2 electrons
- Second level = 8 electrons
- Third level = 18 electrons
- Fourth level = 32 electrons
* The elements are known by their symbols (Latin letters) if the element symbols is one letter it must be written capital.
Ex: Hydrogen (H) oxygen (O) nitrogen (N).
* If the element symbol is two letters is must be written first is capital the second is small.
Ex: sodium (Na) calcium (Ca) neon (Ne).
- Atomic no.: the number of protons or electrons.
- Atomic no: = no of protons = no. of electrons.
- Mass no.: sum of protons and neutrons.
- No. of neutrons = mass no. - atomic no.
- Ex: For the following elements find mass, atomic number.
Protons, electrons and neutrons.
Electronic Configuration
We distribute electrons inside energy levels in sequence according to the atomic numbers.
Note:
In levels after the second we don't put more than eight electrons because this makes the atom more stable.
Elements can be divided into:
1- Active elements: have incomplete energy levels (form compounds with other elements).
2- In active elements: have complete energy levels (don't form compounds with other elements).
The inactive elements are called noble gases (inert gases)
thanks rana 
