Chapter 12
The Periodic Table
Section 1 – Arranging the Elements
Essential Questions
How did Mendeleev arrange the elements in the first periodic table? How are they arranged in the modern periodic table? (12-1)
How do metals, nonmetals, and metalloids compare based on their properties and location on the periodic table? (12-1)
What are the differences between a period and a group? (12-1)
Mendeleev’s First Table
Dmitri Mendeleev created the first Periodic Table of the Elements
1st – sorted known elements by properties such as density, appearance, and melting point.
2nd – put in order of increasing atomic mass, and a pattern appeared
Modern Periodic Table
In 1914, Henry Moseley found the atomic number of each element
Current PTofE is arranged by the atomic number (the number of protons) – thus all elements fit the pattern
Metals
Metals – most elements are metal
Left of the zigzag line
Few electrons
Most are solid at room temperature
Most are shiny
Most are ductile
Most are malleable
Most are good conductors of thermal energy
Nonmetals
Nonmetals – on right of zigzag line
Have almost a complete set of electrons in their outer level
Group 18 (noble gases) have a complete set of electrons
More than half nonmetals are gases at room temperature
Many properties are opposite of metals
Metalloids
Metalloids are also called semi-conductors
Border the zigzag line on the table
Have about half a set of electrons
Have some properties of metals, some of nonmetals
The Periodic Table
Each element has a chemical symbol, an atomic number, the element name, and its’ atomic mass
Each row is called a period
Elements in rows follow a repeating pattern
Columns are called groups or a family
Groups have similar chemical and physical properties
Don’t forget elements combine to form compounds