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