The Periodic Table CHAPTER 10---LESSON # 1 Periodic: repeating, according to a pattern. Ex: days of the week, months, years, etc. Dmitri Mendeleev- “Father of the Periodic Table. Late 1800’s. Arranged PT by the physical and chemical properties of the elements.

Mendeleev arranged the elements in order of increasing atomic mass. The PT is a chart of the elements arranged into rows and columns according to their physical and chemical properties.

Early 1900’s – Henry Moseley Henry Moseley changed the PT to be arranged in order of Increasing Atomic # instead of increasing atomic mass. By doing this, the groups/families then had similar physical And chemical properties ( columns )

Bergmann video on size of atom how_small_is_an_atom#

How is the PT arranged NOW? By increasing atomic number. By their state--solid, liquid or gas at room temperature. By groups – due to their physical and chemical properties. By 3 main groups: metals, metalloids and non-metals

Groups and Periods Groups or Families: 18 of them. They go down ( Vertical ) on the table. Periods: 7 of them. They go across (horizontal ) on the table.

Like a calendar

3 main categories of the PT 1.Metals, Non-metals and Metalloids Most of the table, ¾, are metals. Metals are on the left side of the “staircase,” except for H on the far left. ( NOT A METAL!) Nonmetals, plus H, are to the right of the “staircase.” Many of these are gases. Metalloids are ON the staircase.

The Periodic Law  It states that the chemical and physical properties of elements are periodic or repeating functions of their atomic numbers.