8.P.1.2

Students know:

· how the periodic table of elements is organized and how to use the periodic table in order to obtain information about the atom of an element:

o symbol

o atomic number

o atomic mass

o state of matter at room temperature

o number of outer energy level (valence) electrons.

· how the periodic table of elements is an arrangement of elements according to their properties. The periodic table of elements is arranged horizontally in order of increasing atomic number (number of protons) and vertically in columns of elements with similar

chemical properties. An atom’s identity is directly related to the number of protons in its nucleus. This information can be used to predict chemical reactivity.

· how to use the periodic table as a quick reference for associating the name and symbol of an element.

· how to find the atomic number and atomic mass of an element listed on the table. The periodic table of elements is also an arrangement of elements according to properties. The periodic table is both a tool and an organized arrangement of the elements that reveals the underlying atomic structure of the atoms. The periodic table is a tool that is used in all the domains of science.

· how groups of elements can be classified based on similar properties, including highly reactive metals, less reactive metals, highly reactive non-metals, less reactive non-metals, and some almost completely non-reactive gases. Students understand that substances are often placed in categories together if they react in similar ways. Examples of this in the periodic table include metals, nonmetals, and noble gases. Students know these are major groups of elements that have different physical properties.

· that the information that is organized in the periodic table is based on the observations of many scientists over a long period time. Dmitri Mendeleev is generally credited with the creation of the basis for our modern day table. Mendeleev was not the first to suggest a table, but he was the first to create one that predicted the existence of as-yet-undiscovered elements which were later discovered. As of

2012, the periodic table contains 118 confirmed chemical elements, of which 114 have been recognized by the International Union of Pure and Applied Chemistry (IUPAC) and named.

· that chemical symbols show the atoms of the elements composing a substance. Symbols are written with one, two, or three letters. The first letter is always capitalized. Each element has a different symbol.

o Elements are made up of one kind of atom and the symbol for each element is unique.

o Compounds are composed of more than one element and their formulas have more than one type of symbol showing the different elements that compose the compound.

· that chemical formulas are constructed from the symbols of the elements composing the substances.

o In a chemical formula, the numbers as subscripts show how many of each kind of atom are in the compound.

o The subscript is written to the lower right of the element symbol.

o If no subscript is written, only one atom of that element is part of the compound. For example, in H₂O, the number 2 is the subscript for hydrogen and means that there are 2 atoms of hydrogen in the compound of water; since there is no subscript for oxygen it is assumed to be one atom of oxygen.

· that atoms are composed of 3 subatomic particles- protons, neutrons and electrons. The thing that makes elements different is the number of electrons, protons, and neutrons. The protons and neutrons are always in the nucleus (center of the atom). The electrons are always found around the center in areas called orbitals. Protons have a "+" or positive charge. If the charge of an entire atom is "0", that means there are equal numbers of electrons and protons. Neutrons have a neutral charge (a charge of zero). Electrons have a "-" or negative charge.

Students should recognize common substances such as water (H₂O), carbon dioxide (CO₂), sucrose (C₁₂H₂₂O₁₁), table salt (NaCl), oxygen (O₂), household bleach (NaClO), hydrochloric acid (HCl), ammonia (NH₃), baking soda (NaHCO₃), and vinegar (HC₂H₃O₂, 5% solution) through chemical formulas and symbols.