Chemistry Instructional Guide

Atoms and Elements

Chemistry

Quarter 1

HMHUnit 2

● Electromagnetic emission and absorption are used to determine the composition of stellar objects ● Iron has the greatest nuclear binding energy Reasoning Students apply scientifc principles, along with the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future, to construct their explanation. Students describe the following chain of reasoning used to construct their explanation: ● Fusion is a process in which two nuclei merge to form a single, larger nuclei with a larger number of protons than were in either of the two original nuclei ● Fission is a process in which a nucleus splits into two or more fragments that each have a smaller number of protons than were in the original nucleus ● Hydrogen fuses to form helium, heavier elements are formed through fusion of these elements ● Nuclear stability increases as elements are fused up through iron but decreases for elements heavier than iron ● If resulting nuclei are more stable, a large amount of energy is emitted. If resulting nuclei are less stable, a large amount of energy is needed Standard 1.5 What does it look like to demonstrate profciency on this standard? Components of the model From the given model, students identify and describe the components of the model relevant for predictions, including: ● Elements and their arrangement in the periodic table ● A positively-charged nucleus composed of both protons and neutrons, surrounded by negatively-charged electrons ● Electrons in the outermost energy level of atoms (i.e., valence electrons) ● The number of protons in each element Relationships Students identify the following relationships between components of the given model, including: ● The arrangement of the main groups of the periodic table refects the patterns of outermost electrons ● Elements in the periodic table are arranged by the numbers of protons in atoms. Connections Students relate the patterns of behavior of elements to appropriate components of atomic structure, including:

● The attraction and repulsion between electrically charged particles Students use the model to predict the following patterns of properties:

● The charges of stable ions formed from atoms in main groups of the periodic table ● The trend in reactivity and electronegativity of atoms down a group and across a row in the periodic table, based on attractions of outermost (valence) electrons to the nucleus ● The relative sizes of atoms both across a row and down a group in the periodic table