Which element has 4 energy levels and 7 valence electrons

Five students had to answer the question how are elements arranged in a periodic tabledamon: i think the elements are arranged by increasing massflo: i think the elements are arranged according to their properties sienna: i think the elements are arranged by when their discovers kyle: i think the elements are arranged according to how common they areglenda: i don't agree with any of themwho is right

How many miles of water are produced if 5.43 mol pbo2 are consumed

Which of the following units is not an official si unit