Chapter 5
Section 2:
Exploring The Periodic Table, Part 1
Follow along
The Role of Electrons
〉Why do elements within a group of the
periodic table have similar chemical
properties?
〉The periodic trends in the periodic table
are the result of electron arrangement.
The Role of Electrons, continued
• Valence electrons
account for similar
properties.
• An element’s
location in the
periodic table is
related to electron
arrangement.
▫ Example: Lithium and
sodium, in Group 1, each
have one valence
electron.
Visual Concept: Valence Electrons
Ion Formation
〉What happens to an atom that gains or loses
electrons?
〉If an atom gains or loses electrons, it no longer
has an equal number of electrons and protons.
Because the charges do not cancel completely,
the atom has a net electric charge.
Ion Formation, continued
• Group 1 elements
form positive ions.
▫ The single valence
electron is easily
removed.
• Group 17 elements
form negative
ions.
▫ The addition of one
valence electron fills
the outer energy level.
For Homework
• Page 169 Vocabulary Words
Chapter 5
Section 2:
Exploring The Periodic Table, Part 2
Bellringer
Each square on the periodic table of elements includes
an element’s name, chemical symbol, atomic number,
and atomic mass. Below are examples of elements
found on the periodic table.
Bellringer, continued
1. Which element above has the highest atomic
number? Barium, 56
2. Which element above has the lowest atomic mass?
Magnesium, 12
3. What is the chemical symbol for calcium?
Ca
4. What is the element name for Cr?
Chromium
Open up to page 151 and follow along
How Are Elements Classified?
〉What are the three main categories of
elements?
〉All elements are either metals, nonmetals, or
semiconductors.
How Are Elements Classified?,
continued
• Elements in each category have similar
properties.
▫ metal: an element that is shiny and that conducts
heat and electricity well
▫ nonmetal: an element that conducts heat and
electricity poorly
▫ semiconductor (or metalloid): an element or
compound that conducts electric current better than
an insulator does but not as well as a conductor does
Visual Concept: Comparing Metals,
Nonmetals, and Metalloids
Properties of Metals
• Good conductors of heat & electricity
• They are ductile (can be turned into wires) and
malleable (easily bent or shaped)
• Most are shiny
Properties of Nonmetals
• Poor conductors of heat & electricity
• Not malleable or ductile
• Most are not shiny
Properties of Semiconductors
• Share properties of metals and nonmetals
• Conduct electricity under certain conditions
• Main components in computer chips and other
electronic devices
How Are Elements Classified?,
continued
For Homework
• Section Review, 1-8, page 155