Chemical Interactions
Chapter 1 Atoms and Bonding
Section 2 Atoms, Bonding, and the Periodic Table
Key Concepts:
1. How is the reactivity of elements related to valence electrons in
atoms?
2. What does the periodic table tell you about atoms and the
properties of atoms?
Key Terms:
• Valence Electrons
• Electron Dot Diagram
• Chemical Bond
• Symbol
• Atomic Number
• Period
• Group/Family
• Noble Gas
• Halogen
• Alkali Metal
Valence Electrons and Bonding
Valence Electrons- Electrons left in the furthest energy level.
Held the most loosely.
The number of valence electrons an atom has determines
many properties:
• How atoms will bond with other atoms
• Remember the first energy level can hold 2 electrons
• Each energy level after the first can hold 8 electrons
Valence Electrons and Bonding
Electron Dot Diagram – Symbol of the element and dots
representing the valence electrons. (1-8)
 Chemical Bond- Force of attraction
that holds two atoms together as a
result of the electrons rearrangement
between them.
This causes a new substance to
be formed…which is a chemical
reaction.
•Electrons can be transferred
to another atom
•Electrons can be shared
between atoms
Elements need to
have their last
energy level
completely full to
become STABLE .
Atoms react with one another to
try and become stable.
They can either increase their
valance electrons to eight (8)
Or give up loosely held valance
electrons to move down an
energy level.
Periodic Table of Elements
 Organization of elements into categories
 Understanding the table will help you:
 know the number of valence electrons each element has
 how the elements will combine with other elements
Periodic Table of Elements
Symbol- One or two letters
representing an element on the
periodic table
Atomic Number
16
S
Sulfur
32.06
Atomic Number- Number of
protons in the nucleus of an
atom.
• Also the number of electrons
that fill the electron energy
Symbol
levels
• Subtract this from the
Atomic
Atomic Mass to get the
Mass
number of Neutrons
Periodic Table of Elements
Period- Row of elements across the periodic table
Group/Family- columns of elements down the periodic table.
Valence electrons increase as you go across the periodic table
Elements in the same Group/Family will have the same amount of valence
electrons
• 1- 2-3-4-5-6-7-8
 The period that the element is in will have the same number of energy
levels
•1
•2
•3
•4
Periodic Table of Elements
Elements in the same group/family share similar qualities
Noble Gases- Group 18. Have eight (8) valence electrons. Do not react easily.
 Helium has two (2) but is only in the first energy level
 Neon
 Argon
 Krypton
Halogens- Group 17. Have seven (7) valence electrons. React highly with
elements that give up or share one (1) valence electron.
 Fluorine
 Chlorine
 Iodine
Alkali Metals- Group 1. Have one (1) valence electron. Lose or share the valence
electron easily to move down an energy level making them stable.
 Lithium
 Sodium
 Potassium
Periodic Table of Elements
Other Metals- Groups 2-12. Have one, two, or three (1,2, or 3) valence electrons.
Most lose their electrons, the lower the group number the higher the chance they
lose.
 Alkaline Earth Metals- Group 2 are reactive
 Platinum (Group 10) and Gold (Group 11) are not reactive
Other Nonmetals- Have four (4) or more valence electrons. Either combine with
metals and gain electrons or combine with other nonmetals by sharing electrons.
Green Section of the book’s periodic table (Always a different color)
 Covers multiple groups/families
Metalloids- Have three to six (3-6) valence electrons. Can lose or share valence
electrons. Can be metal or nonmetal depending on conditions.
 Yellow Section of the book’s periodic table (Always a different color)
 Fall between metals and non metals
Hydrogen- Has one (1) valence electron, but has different properties than the other
Alkali Metals in Group 1 because it can gain one (1) valence electron to become
stable at two (2).
Chapter 1 Atoms and Bonding
Section 2 Atoms, Bonding, and the Periodic Table
1. How is the reactivity of elements related to valence electrons in atoms?
2. What does the periodic table tell you about atoms and the properties of atoms?
 Section Review page 20