Chapter 6 Chemical Bonds

Valence Electron Remember from chapter 5 we learned that elements that are in the same group have similar properties and behave the same because they have the same number of outer electrons. Outer electrons = valence electrons Valence electrons(ve - )- is an electron that is in the highest occupied energy level of an atom

Valence electrons play a key role in chemical reactions The number of valence electrons largely determines the chemical properties of an element. To find the number of valence electrons in an atom of a representative element, simply look at its group number. Ex: 1A (group 1)= 1 valence electron 2A (group 2)= 2 valence electrons 3A (group 13) = 3 valence electrons

Groups - Review Each column is called a “group” Each element in a group has the same number of electrons in their outer orbital, also known as “shells”. Except for He, it has 2 electrons The electrons in the outer shell are called “valence electrons”

How many valence electrons does the following elements have? B = ______S = ______Cl = ______ He = ______ Elements in a group have similar properties because they have the same number of valence electrons.

Electron dot diagrams Electron dot structures (diagram)- is a model of an atom in which each dot represents a valence electron. The symbol in the center represents the nucleus and all the other inner electrons. Example: Hydrogen is in Group 1A so it has 1ve - Lewis Dot diagram = H∙

Drawing an Electron Dot Diagram 1.Write the element’s symbol. 2.Calculate the number of valence electrons for the element. 3.Place dots around the symbol to represent the valence electrons. 4.Place in the correct order. 5.The dots get placed in the following order: Right, left, top, bottom and repeats or the second round goes top, bottom, right, left.

When the highest occupied energy level of an atom is filled with electrons, the atom is stable and not likely to react. The noble gases are stable because they have a complete octet. This means they have the maximum number of valence electrons in their outer most shell, which is eight (except for helium which can only have 2 valence electrons. Example: Neon