Valence Electrons

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Valence Electrons

Chemistry is a study of different atoms, an atom is the smallest particle in matter. An atom consists of three major subatomic particles, which are electrons, neutrons and protons. The protons are the positively charged particles. The neutrons are the neutral particles. The electrons are the negatively charged particles. The neutrons and protons are located inside the nucleus of the atom. An atom has nucleus in the center, around the nucleus are electrons arranged in various orbits depending on the atomic number.

Valence electrons definition:

Every atom has a unique atomic number. The number of electrons an atom has is equal to the atomic number of the atom. Initially the atom fills electrons in the inner most orbit and then the outer orbits. Theses electrons are arranged in orbits around the nucleus. The electrons that are present in the outermost shell of the atom are called as the valence electrons. Identifying the number of valence electrons for each atom is a very useful concept which can be applied in chemical bonding and many other chemistry topics.
The following is a table to understand the number of valence electrons the atoms in the periodic table have:
Periodic Table Group Number of valence electrons
The Alkali metals (Group I) 1
The Alkaline earth metals (Group II) 2
The transition metals (Group 3 to 12) 3-12
Group III 3
Group IV 4
Group V 5
Group VI 6
The Halogens 7
Noble Gases Group (VIII) 8

Writing Electronic Configuration for finding the valence electrons:

The electronic configuration of an atom can be written according its atomic number. The number of electrons of an atom are arranged in sub energy levels at the ground state of the atoms. The electronic configuration of an atom starts by filling the lower sub energy levels. Given below is the chart that helps to identify how the electrons are filled and the order in which the electronic configuration is written:
valence electron
So the order in which the electrons are filling is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s and so on.
Valence electrons of few atoms:
The following are examples of finding the number of valence shell electrons using the electronic configuration of the given atom.
Valence electrons of Hydrogen:
·         The atomic number of Hydrogen is 1.
·         The electronic configuration for Hydrogen is 1s1.
·         The number of valence electrons is 1. Since the 1s shell is the outermost shell it has only one electron in it. The orbits for the Hydrogen atom looks like this:
valence electron
Valence electrons of Helium:
·         The atomic number of Helium is 2.
·         The electronic configuration for Helium He is 1s2.
·         The number of valence electrons is 2. The number of electrons it has is 2.
The diagram for the Helium atom looks like this:
valence electron                       
Valence electrons of Lithium:
·         The atomic number of Lithium is 3.
·         The electronic configuration for Lithium Li is 1s2, 2s1.
·         The outermost shell of Lithium is 2s. The number of valence electrons is has 1.
The diagram for the Helium atom looks like this:
valence electron
Valence electrons of Beryllium:
·         The atomic number of Beryllium is 4.
·         The electronic configuration for Beryllium Be is 1s2, 2s2.
·         The outermost shell of Beryllium is 2s. The number of valence electrons is has 2. The diagram for the Beryllium atom looks like this:
valence electron 
Valence electrons of Boron:
·         The atomic number of Boron is 5.
·         The electronic configuration for Boron B is 1s2, 2s2, 2p1.
·         The outermost shell of Boron is n = 2. The total number of valence electrons it has is 3. The diagram for the Boron atom looks like this:
boron
Valence electrons of Carbon:
·         The atomic number of Carbon is 6.
·         The electronic configuration for Carbon C is 1s2, 2s2, 2p2.
·         The outermost shell of Carbon is n = 2. The total number of valence electrons it has is 4. The diagram for the Carbon atom looks like this:
Carbon 
Valence electrons of Nitrogen:
·         The atomic number of Nitrogen is 7.
·         The electronic configuration for Nitrogen is N 1s2, 2s2, 2p3.
·         The outermost shell of Nitrogen N is n = 2. The total number of valence electrons it has is 5. The diagram for the Nitrogen atom looks like this:
Nitrogen
Valence electrons of Oxygen:
·         The atomic number of Oxygen is 8.
·         The electronic configuration for Oxygen O is 1s2, 2s2, 2p4.
·         The outermost shell of Oxygen is n = 2. The total number of valence electrons it has is 6. The diagram for the Oxygen atom looks like this:
Oxygen
Valence electrons of Fluorine:
·         The atomic number of Fluorine is 9.
·         The electronic configuration for Fluorine F is 1s2, 2s2, 2p5.
·         The outermost shell of Fluorine is n = 2. The total number of valence electrons it has is 7. The diagram for the Fluorine atom looks like this:
fluorine
Valence electrons of Neon:
·         The atomic number of Neon is 10.
·         The electronic configuration for Neon Ne is 1s2, 2s2, 2p6.
·         The outermost shell of Neon is n = 2. The total number of valence electrons it has is 8. The orbits of Neon atom looks like this:
Neon
Valence electrons of Sodium:
·         The atomic number of Sodium is 11.
·         The electronic configuration for Sodium Na is 1s2, 2s2, 2p6, 3s1.
·         The outermost shell of Sodium Na is n = 3. The total number of valence electrons it has is 1. The orbits of Sodium atom looks like this:  
Sodium
Valence electrons of Magnesium:
·         The atomic number of Magnesium is 12.
·         The electronic configuration for Magnesium Mg is 1s2, 2s2, 2p6, 3s2.
·         The outermost shell of Magnesium Mg is n = 3. The total number of valence electrons it has is 2. The orbits of Magnesium atom looks like this:  
Magnesium
Valence electrons of Aluminum:
·         The atomic number of Aluminum is 13.
·         The electronic configuration for Aluminum Al is 1s2, 2s2, 2p6, 3s2, 3p1.
·         The outermost shell of Aluminum Al is n = 3. The total number of valence electrons it has is 3. The orbits of Aluminum atom looks like this:  
Aluminium
Shown above are the valence electrons for atoms with atomic number 1 to 13.  The same concept applies for finding the valence electrons of all the atoms in the periodic table.

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