3. Express the following numbers in scientific notation, making sure there is only one nonzero digit to the left of the decimal place. Do not discard any nonzero digits.
a) 0.000890
b) 35470

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.