1sotopes

• Isotopes have the same atomic number and a different mass number
• Isotopes are different forms of the same element.
• They have the same number of protons and a different number of neutrons.
• Before the discovery of protons, neutrons and electrons scientists tried to classify the elements in order of the atomic mass.
• The early periodic tables were incomplete. Many elements were missing as many elements had not yet been discovered.
• because they followed atomic mass elements were not placed in groups of the elements with similar properties.
• The metals and the nonmetals got mixed up to.
• John newlands law of octaves elements are arranged in order of increasing atomic mass
• Newland Octavius, he saw that every eight elements reacts in a similar way
• As sometimes when they were grouped together when they had totally different properties
• DMITRI MENDLEEV all periodic table arranged in order of increasing atomic weight
• Secondly he realised that some elements had not been discovered so he left gaps in the periodic table
• If he needed to MENDELEEV would switch the order of Pacific elements. So they fitted the patterns of other elements in the same group.
• He was confident that his table was correct that he predicted the properties of the undiscovered elements based on other elements in the same groups
• Because of that other scientist excepted his periodic table
• . When we ordered the elements by atomic number every element is in the correct group.
• Elements in the same group of the periodic table has similar properties.