1. It looks like rain. We should shut the windows. 2. Ann, can/could you hand me that dish? 3. I returned a book to the library yesterday. It was 2 weeks overdue, so I had to pay a fine of $ 1.40.4. I must return the books when they are due. 5. Spring break starts on the 13 . We don't have to go to classes again until the 22 .6. Could I make an appointment to see Dean Witherspoon? 7. Neither of us knows the way to their house. We should take a map with us or we'll probably get lost.8. The baby is only a year old, but can/is able to say already a few words .9. You should not tell Jack about the party. Its a surprise birthday party for him.10. Excuse me, I didnt understand. Could/can you repeat what you said?
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.
