The Periodic Table
The periodic table organises all known elements by their atomic number and chemical properties. Developed by Dmitri Mendeleev in 1869, it reveals patterns in element properties and predicts the behaviour of elements and compounds.
What You Need to Know
Key Concept Diagram
An element is a substance made of only one type of atom; elements cannot be broken down by chemical means
Elements are arranged in order of increasing atomic number (number of protons)
Rows in the periodic table are called periods; columns are called groups
Elements in the same group have similar chemical properties because they have the same number of valence electrons
Metals (left side) are generally shiny, conduct electricity, and are malleable; non-metals (right side) have opposite properties
Key Vocabulary
Element
A pure substance made of only one type of atom; cannot be broken down by chemical reactions
Atomic Number
The number of protons in the nucleus of an atom; uniquely identifies each element
Period
A horizontal row in the periodic table; elements in the same period have the same number of electron shells
Group
A vertical column in the periodic table; elements in the same group have similar chemical properties
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
What does the atomic number of an element tell you?
Question 2
Why do elements in the same group of the periodic table have similar properties?
Question 3
Sodium (Na) is in Group 1 of the periodic table. Which property would you expect it to have?
Key Concepts Summary
- ●An element is a substance made of only one type of atom; elements cannot be broken down by chemical means
- ●Elements are arranged in order of increasing atomic number (number of protons)
- ●Rows in the periodic table are called periods; columns are called groups
- ●Elements in the same group have similar chemical properties because they have the same number of valence electrons
- ●Metals (left side) are generally shiny, conduct electricity, and are malleable; non-metals (right side) have opposite properties