Which of the following best describes why the atomic model has changed repeatedly over the past 200 years? 1. most of the models were huge mistakes. 2. very few people thought the models were valid. 3. the models were known to be incomplete and needed to be fixed. 4. the results of further experimentation to revise and improve the model.

Darla claims that the first periodic table developed by mendeleev was not completely accurate, so it is not useful at all. harmony argues that it establish the periodic table we use today, making it more credible. who is correct and why? darla is correct, because a model that has any mistakes should be thrown out. darla is correct, because a good model would not need to change. harmony is correct, because mendeleev’s model had all of the information correct in the first version. harmony is correct, because mendeleev’s model made predictions that came true.

Which property of a rock remains unchanged by mechanical weathering? a. total surface area b. size and shape c. mineral composition d. sharpness

Who examines and coordinates the cleanup of polluted sites?