The Periodic Table

1. The Periodic Table Atoms and Elements

2. Matter • Matter is anything that has mass and takes up space. • Matter is described by its properties. Some of the properties that can be described are those that you investigated when made your matchbook element: atomic number, atomic mass, weight, color, state, structure, shells, boiling point, melting point, density, reactivity, thermal conductivity, electrical conductivity, pH • These properties are called physical and chemical properties. • Physical properties are characteristics that can be used to describe matter without changing it. Chemical properties are properties that describe how the matter changes when placed in the presence of other matter or energy (flammability, reactivity)

3. Properties and the Periodic Table • A scientist name Dmitri Mendeleev noticed that if he organized the matter he studied in order by atomic mass, he could see the matter formed groups based on similar properties. • Since Mendeleev’s work, the table has been modified and arranged according to atomic number. • The matter that Mendeleev was describing was what we call elements. Elements are matter that cannot be broken down into other substances by any chemical means. • When elements are arranged by atomic number in a chart like the periodic table, patterns appear of elements with similar physical and chemical properties. We call elements that have similar properties families.

4. The Periodic Table • A box on the table looks like Atomic Number 1 H Element Symbol Element Name Hydrogen 1.008 Atomic Mass

5. Inside The Box • Atomic number – The number of protons an element has • Element Symbol – The shorten way to write an element’s name usually with one or two letters. The first is capitalized. • Element Name – The name of the element • Atomic Mass – The average mass of the element’s atoms the unit is much, much smaller than a gram so its unit is atomic unit or aµ

6. Organization of the Table • Is arranged by atomic number • The vertical columns are called groups. There are 18 groups. Groups are also known as families. Each group has a number 1-18. • Elements in the same group or family has similar properties. • The periodic table also has horizontal rows called periods. A period has different types of elements from different families. • As you move across, the period the elements’ properties gradually change. For example from highly reactive to less reactive. • This arrangement of the periodic table allows us to predict characteristics of elements due to position in the table