Periodic Table Key Concepts

Periodic Table Basics

 The periodic table is a table of all the elements which make up matter  Elements initially grouped in a table by Dmitri Mendeleev  Symbols – each element has a symbol which is either a Capital Letter or a Capital Letter followed by a lower case letter  Atomic Number – the number above an element’s symbol which shows the number of protons  Atomic Mass – the number found below an elements symbol which shows the mass of the element. Mass = the number of protons + the number of neutrons  Metals – the elements which have the properties of malleability, luster, and conductivity o These elements are good conductors of electricity & heat. o Found to the left of the zig-zag line on the periodic table  Nonmetals – do not have the properties of metals. Found to the right of the zig-zag line  Metalloids – elements found along the zig-zag line of the periodic table and have some properties of metals and nonmetals (B, Si, Ge, As, Sb, Te, and Po) Groups

 The columns going up and down (There are 18 groups)  Group 1: Hydrogen, Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium  Elements arranged so that elements with similar properties would be in the same group. o Group 1 Alkali Metals - highly reactive metals o Group 2 Alkali Earth Metals – reactive metals o Group 3-12 Transition Metals o Group 17 Halogens – highly reactive non-metals o Group 18 Noble Gases - do not react or combine with any other elements.  Elements are grouped according to their properties or reactivity  Reactivity is determined by the number of electrons in an element’s outer energy level  These electrons are called valence electrons Periods

 The rows that run from left to right on the periodic table (There are 7 periods)  Period 1 contains 2 elements, Hydrogen and Helium.  Period 2 contains 8 elements: Lithium, Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine, Neon  The different periods represent different electron energy levels. o Elements in period 1 have electrons in just one energy level. o Elements in period 2 have electrons within two different energy levels. Periodic Trends

 Metallic properties – the properties that define a metal tend to increase going to the left and down on the periodic table (malleability, luster, and conductivity)  Atomic mass – increases going to the right and down on the periodic table  Atomic radius – increases going down on the periodic table Periodic Table Key Concepts