Unit 3 Valence Electrons and Ions

Subatomic Particles In an atom Protons and neutrons are clumped together in a very small dense nucleus In an atom Protons and neutrons are clumped together in a very small dense nucleus The Electrons are found outside of the nucleus in various electron clouds The Electrons are found outside of the nucleus in various electron clouds

Principle Energy Levels The electron clouds are found at specific distances from the nucleus called Principle Energy Levels The electron clouds are found at specific distances from the nucleus called Principle Energy Levels Lowest energy levels are closest to the nucleus Lowest energy levels are closest to the nucleus Highest energy levels are farthest from the nucleus Highest energy levels are farthest from the nucleus Fill from Lower  Higher energy levels Fill from Lower  Higher energy levels

Energy Level ‘Clouds’ phycomp.technion.ac.il/~phr76ja/lecture1.html hoku.as.utexas.edu/.../a309f04/lect1cos.html

Bohr The Bohr model is used to show electron placements in the energy levels. The Bohr model is used to show electron placements in the energy levels. Elements in the same row of the periodic table have the same number of occupied energy levels Elements in the same row of the periodic table have the same number of occupied energy levels

Energy Levels First energy level- max 2 electrons Second energy level- max 8 electrons Third energy level- max 8 electrons Fourth energy level- max 18 electrons

Valence Electrons The electrons that occupy the highest energy level (or the outer shell) are called Valence Electrons The electrons that occupy the highest energy level (or the outer shell) are called Valence Electrons Valence electrons are important because they are the electrons involved in chemical reactions Valence electrons are important because they are the electrons involved in chemical reactions This means that the number of valence electrons determines an element’s chemical properties This means that the number of valence electrons determines an element’s chemical properties

Valence Electrons Elements in the same column of the Periodic Table have the same number of valence electrons and have similar chemical properties. Elements in the same column of the Periodic Table have the same number of valence electrons and have similar chemical properties.

Ions When elements undergo chemical reactions they either share or exchange electrons with other elements to fill their outer shells. When elements undergo chemical reactions they either share or exchange electrons with other elements to fill their outer shells. Atoms that have either lost or gained electrons are called ions. Atoms that have either lost or gained electrons are called ions. Unlike neutral atoms, ions have a net charge. Unlike neutral atoms, ions have a net charge.

Ion Charges The number of electrons that it has lost or gained determines an ion’s charge The number of electrons that it has lost or gained determines an ion’s charge Ions that GAIN electrons have a NEGATIVE charge and are called anions. Ions that GAIN electrons have a NEGATIVE charge and are called anions. Ions that LOSE electrons have a POSITIVE Charge and are called cations. Ions that LOSE electrons have a POSITIVE Charge and are called cations.

Lithium Loses an Electron Li  Li e- Li Li +1

Fluorine gains an electron F + 1 e-  F -1 F F -1

Lithium Fluoride F + 1 e-  F -1 Li  Li e- Li + F  LiF

HCl Draw Bohr Models for Hydrogen and Chlorine and then show how they combine. Draw Bohr Models for Hydrogen and Chlorine and then show how they combine. Cl + 1 e-  Cl -1 H  H e- H + Cl  HCl

Ion Drawings Draw Bohr models for the following elements: Draw Bohr models for the following elements: –Oxygen –Sodium –Magnesium –Bromine

Ion Drawings In your lab groups draw Bohr models for the following elements: In your lab groups draw Bohr models for the following elements: –Oxygen (2) –Hydrogen (2) –Sodium (1) –Chlorine (1) –Magnesium (1) –Calcium (1) –Bromine (2)

Combine Ions Cut out the circles and combine the Ions to make the following compounds. Draw arrows to show the movement of the electrons Cut out the circles and combine the Ions to make the following compounds. Draw arrows to show the movement of the electrons –H 2 O Water –NaClSodium Chloride –CaBr 2 Calcium Bromide –MgOMagnesium Oxide