In developing his periodic table, Dmitri Mendeleev arranged the elements primarily in order of increasing atomic mass. Which of the following describes how he grouped the elements and handled undiscovered elements?
He grouped elements with similar chemical properties together and left gaps for elements that had not yet been discovered.
He grouped elements by their atomic numbers and left gaps for elements that had not yet been discovered.
He grouped elements by their physical state (solid, liquid, or gas) and ensured there were no empty spaces.
He grouped elements with similar chemical properties together and filled every position without leaving any gaps.
77 exam-style questions on OCR GCSE Chemistry Atomic structure. Each one has a worked solution and a mark scheme showing where the marks go.