CHAPTER 8Lesson 1- Electrons and Energy levels

THE PERIODIC TABLE

Library of information about the elements Contains basic properties about the element

like State of matter at Room Temperature Atomic Number Atomic Mass

PERIODS AND COLUMNS

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

METALS

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

NONMETALS

Groups 14-18 Poor Conductors of electrical and thermal

energy Most are gases at room temperature If a solid then often brittle

METALLOIDS

Have properties in common with both metals and nonmetals

Often used in semiconductors

COMPOUNDS

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

ELECTRON NUMBER AND ARRANGEMENT

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

ELECTRONS 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

ELECTRONS 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

VALENCE ELECTRONS

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 3- 12 vary in the number of valence

electrons Group 13-18- the valence electrons equal the

one’s digit

ELECTRON DOT DIAGRAMS/LEWIS STRUCTURES

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

ELECTRON 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

NOBLE GASES

Group 18 Have 8 valence electrons in outer orbital Do not react chemically

STABLE AND UNSTABLE ATOMS

8 electrons in outer orbital- stable Less than 8 electrons in outer orbital then

chemically reactiveChemical bonds can form by sharing, gaining,

or losing electrons