While I was walking along the street, I saw a house was on fire. There were a lot of people who were screaming and running around the house. Some people were running out the house and firefighters were running in. An ambulance came and doctors were ready to help. This house was about to break down. It was a very beautiful building. It was built two hundred years ago. This house used to belong some famous family. However, firefighters worked well. They managed to put out the fire quickly and they saved the building. Everybody was happy.
1. Dmitri Mendeleev developed the concept of the periodic repetition of properties. 2. There are 8 columns in the periodic table. In each column, elements are arranged by the same properties, such as the same orbital arrangement of electrons. 3. Mendeleev predicted properties of yet undiscovered (missing) elements and left empty spaces for them in the table. 4. There are natural groupings between the elements that are closely related to each other. 5. In order to understand better these natural groupings, chemists have tried to fit the elements into a single plan. 6. John Ncwlands made one of the first attempts to fit the relationships among the elements by suggesting the Law of Octaves.
2. There are 8 columns in the periodic table. In each column, elements are arranged by the same properties, such as the same orbital arrangement of electrons.
3. Mendeleev predicted properties of yet undiscovered (missing) elements and left empty spaces for them in the table.
4. There are natural groupings between the elements that are closely related to each other.
5. In order to understand better these natural groupings, chemists have tried to fit the elements into a single plan.
6. John Ncwlands made one of the first attempts to fit the relationships among the elements by suggesting the Law of Octaves.