12 B IG I DEA 1: A TOMIC S TRUCTURE AND P ERIODICITY Big Idea 1 The chemical elements are fundamental building materials of matter, and all matter can be understood in terms of arrangements of atoms. These atoms retain their identity in chemical reactions. Atoms are the fundamental building blocks of the elements which comprise all matter. Big Idea 1 relates to 3 main topics in this chapter: atomic structure, periodicity, and macroscale matter. The structure of the atom is the basis for the organization of the elements on the periodic table. Physical and chemical changes that we see on the macroscopic scale are the result of how atoms interact with other atoms and with electromagnetic radiation. Because atoms are so incredibly small we use moles as a unit of measurement when describing quantities of atoms. You should be able to Use evidence to explain why atomic models have changed throughout history. Calculate the average atomic mass of an atom from mass spectrometry and isotopic data. Use photoelectron spectroscopy as evidence to show that electrons exist in quantized shells. Justify the arrangement of the periodic table based on the quantum mechanical model of the atom.
B IG I DEA 1: A TOMIC S TRUCTURE AND P ERIODICITY N N 13 Convert between mass, moles, and numbers of representative particles (atoms, molecules, formula units) of a substance. Calculate the molar mass of a compound and the percent composition of an element in a compound. Express the law of conservation of mass using symbolic representations and particulate models. AP Tip Writing coherent answers to the free-response questions is essential. You need to differentiate between restating facts and explaining the concepts and evidence that supports the facts. Questions that involve mathematical problem solving should clearly show your work and answer. Partial credit may be awarded for some questions. P ART 1: A TOMIC S TRUCTURE E VIDENCE FOR A TOMS M ODELS C HANGE O VER T IME Atomic models have been around since Democritus first thought about dividing matter by continually cutting it into smaller and smaller pieces until it could no longer be cut: atomos . The idea of atoms was opposed by Aristotle and it took about 2500 years until scientific evidence was used to revive the idea of atoms. H ISTORY OF THE A TOM ( Chemistry 8th ed. pages 42–50/9th ed. pages 44–54) J OHN D ALTON Dalton’s model of the atom was based on the work of many scientists. He used the law of definite proportion and the law of multiple proportions to provide evidence for his model. Dalton’s model has 4 parts: 1. Each element is made of atoms. 2. Atoms of a given element are identical; atoms of different atoms are different in some fundamental ways. 3. Atoms can combine to form compounds and a given compound always has the same relative number and types of atoms.
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