C HAPTER 8 Lesson 1- Electrons and Energy levels

T HE P ERIODIC T ABLE Library of information about the elements Contains basic properties about the element like State of matter at Room Temperature Atomic Number Atomic Mass

P ERIODS AND C OLUMNS Periods-horizontal Start at metals, then transition metals, metalloids, non metals and noble gases Columns- vertical Called groups or families Have similar chemical properties to other members in the family

M ETALS Group 1 to 12 Often Shiny Good conductors of electricity Ductile- easily pulled into thin wires Can be hammered into thin sheets

N ONMETALS Groups Poor Conductors of electrical and thermal energy Most are gases at room temperature If a solid then often brittle

M ETALLOIDS Have properties in common with both metals and nonmetals Often used in semiconductors

C OMPOUNDS Two or more elements that are chemically combined There are 115 elements but millions of compounds A chemical bond is a force that holds two or more atoms together

E LECTRON NUMBER AND A RRANGEMENT The number of electrons equals the number of protons in a neutral atom You can determine the position of an electron because electrons are in constant motion around the nucleus However, it is known that some electrons are closer to the nucleus and others are farther away

E LECTRONS AND ENERGY Different electrons have different amounts of energy Electrons nearest the nucleus have the lowest amount of energy The farther from the nucleus then higher the energy level In the 1s level you can have 2 electrons In the 2s level you can have 2 electrons In the 2p level you have 6 electrons In the d levels 10 electrons In the f levels 14 electrons

E LECTRONS AND BONDING Electrons in the outer most levels are attracted to the protons in the nucleus of another atom Opposites attract A chemical bond can form when the electrons from one atom are attracted to the protons of another atom

V ALENCE E LECTRONS Outermost electrons involved in chemical bonding Valence electrons have the most energy The number of valence electrons can determine what type of bonds an atom can form Group 1 have 1 valence electron Group 2 has 2 valence electrons Groups vary in the number of valence electrons Group the valence electrons equal the one’s digit

E LECTRON D OT DIAGRAMS /L EWIS S TRUCTURES Chemist Gilbert Lewis in 1916 developed a method to show the valence electrons. He developed the electron dot diagram which shows the valence electrons as dots around the chemical symbol

E LECTRON DOT DIAGRAM RULES 1. Identify the group number on the periodic table 2. Identify the number of valence electrons 3.Place one dot on each side of the symbol going (top, right, bottom, left) Repeat 3 until all the dots are used 4. Determine if the atom is chemically stable 5. Determine how many bonds the element can make Count the number of unpaired dots

N OBLE G ASES Group 18 Have 8 valence electrons in outer orbital Do not react chemically

S TABLE AND UNSTABLE ATOMS 8 electrons in outer orbital- stable Less than 8 electrons in outer orbital then chemically reactive Chemical bonds can form by sharing, gaining, or losing electrons