Organizing the Elements Section 1: Organizing the Elements

Periodic – repeating according to some pattern In his periodic table, Mendeleev arranged elements in rows by increasing atomic mass. Mendeleev was able to predict new elements and left spaces in his table to make the pattern fit and successfully predict the existence and properties of elements not yet discovered.

The modern periodic table organizes elements by atomic number. When the elements are arranged in this way, elements that have similar properties appear at regular intervals (periodic) periodic law: the law that states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements

Changing the Arrangement period: a horizontal row of elements in the periodic table Elements become less metallic across each period. group: a vertical column of elements in the periodic table; elements in a group share chemical properties Elements in a group have similar properties.

Exploring the Periodic Table Section 2: Exploring the Periodic Table

The Role of Electrons The periodic trends in the periodic table are the result of electron arrangement. Valence electrons account for similar properties. If an atom gains or loses electrons, it no longer has an equal number of electrons and protons. Because the charges do not cancel completely, the atom has a net electric charge.

created when electrons are removed. Ion Formation Cations positive ions created when electrons are removed. Anions - negative ions created when electrons are gained

Elements are classified in one of the following ways: metal: an element that is shiny and that conducts heat and electricity well nonmetal: an element that conducts heat and electricity poorly semiconductor (or metalloid): an element or compound that conducts electric current better than an insulator does but not as well as a conductor does

Properties of Metals

Properties of Nonmetals

Properties of Semiconductors (AKA  Metalloids)

Section 3: Families of Elements

In general, the elements in a family have the same number of valence electrons.

Families of metals alkali metal: one of the elements of Group 1 of the periodic table, has only 1 valence electron alkaline-earth metal: one of the elements of Group 2 of periodic table, has 2 valence electrons transition metal: one of the metals that can use the inner shell before using the outer shell to bond

Families of nonmetals The noble gases are relatively inert or unreactive, because their s and p orbitals are filled. In general, they do not form ions or compounds. The halogens combine easily with metals to form salts. Halogen means “salt former” Have 7 valence electrons

Semiconductors As their name suggests, they are able to conduct heat and electricity under certain conditions. AKA  Metalloids They are located in the stairstep