Science : Chemistry : Additional Science

• Protons And Neutons in Atom Nucleus
• Atomic Number = number of Protons.
• All Atoms of an Element have same amount protons.
• Mass Number =  Protons No. + Neutron No.
• Isotope: Two or more forms of an element ,with different neutron numbers.

                   Relative Charge         Relative Mass 

 Proton          +1                                 1             Postive

 Neutron          1                                 0             Neutral

 Electron        1/1836                          -1            Negative

• 1896,Dmitri Mendeleev arranged the element in this time in a table,in order of increasing mass(In Periods(Rows)).
• Placed elements with similar proporties in the same column (Groups).
• He left gaps in the table to allow elements to fit the patteren.
• Correctly predicted new elements would be discovered to fill the gaps.
• Was able to predict properties of these element by looking at properties ofelements surrounding the element. 

• No. of Electrons = No. of Protons.
• The nearer the nucleus , low energy in the electrons.
• Electrons arrange in shells around the nucleus
• First shell can hold 2 electrons,Second and rest can hold 8 electrons.
• Electrons in the same group , have the same number of electrons in their outer shell
• Number of elements