Lesson 2 — Activity 1: Elements
Completion requirements
Lesson 2 — Activity 1: Elements
Explore
An element is the simplest form of matter in that it cannot be further broken down using any chemical means. Elements contain only one type of atom. By the 1860s, scientists had discovered 64 elements and had recorded many of their properties.
In this activity, you will learn about elements and their properties and how elements are organized.
In 1869, a scientist by the name of Dmitri Mendeleev first worked to organize the elements he knew of. He wrote all of the information for each element on a separate file card and then put elements that had similar properties into columns. He organized the elements within each group from the lightest to the heaviest. Then he organized the groups so that the lightest elements were on the left side of the table and the heaviest were on the right side.
As he was working, Mendeleev noticed that some elements appeared to be missing. He predicted that these elements existed but had not yet been discovered. Mendeleev made cards for the missing elements and even predicted their properties. This work provided the basis for what is called the periodic table. This is a chart on which scientists have organized all of the elements.
Mendeleev worked with 64 elements. Since that time, the number of known elements has grown to 112. As scientists continued to investigate, new elements were discovered and many were the elements that Mendeleev had predicted. Even with modern advances in scientific techniques, the way the periodic table is arranged has not changed much from the way Mendeleev first designed it.
The elements in Mendeleev’s chart are made up of atoms. Atoms are the smallest bits of matter. For example, water is made up of atoms of hydrogen and oxygen. For each atom of oxygen, water has two atoms of hydrogen.
Periodic tables do not all look the same, but they do have some of the same things in common:
- They all look like a chart.
- Each square of the table includes information about one element.
The amount of information varies depending on who made the table, but each square usually contains an element’s symbol and name.
Some tables include information such as the element’s state, its complete name, and details about the atoms that make up the elements.
Here's an example of a periodic table.
Digging Deeper
Click on the Play button to watch a video that explains how to read a periodic table. You will note that the table in the video looks slightly different than the one pictured above. Remember that periodic tables do not all look the same but contain similar information.
Self-Check
Try This!
Try the questions below on your own first and then click on the tab to check your answers!
Decide if the following statements are true or false.
1. By the 1860s, scientists had discovered 112 elements and had recorded many of their properties.
2. A scientist named Mendeleev was one of the first scientists to organize elements and provided the basis for the periodic table.
3. The elements in Mendeleev’s chart are made up of atoms.
4. All periodic tables look exactly the same.
1. False. By the 1860s, scientists had only discovered 64 elements.
2. True
3. True
4. False. Many tables look different but have similarities.
Digging Deeper
The video above provided information on elements that were designated metals, non-metals, and metalloids.
Think back to the various physical and chemical properties you studied in the last lesson.
These properties help us distinguish metals from non-metals.
1. Metals are good conductors of heat and electricity. They can be bent, stretched into a wire, or polished until shiny. They are solids at room temperature, except for mercury, which is a liquid.
copper
lead
tin
nickel
iron
zinc
2. Non-metals are poor conductors of heat and electricity. They are dull in appearance. Most are gases at room temperature, except for bromine, which is a liquid.
nickel
iron
zinc
oxygen
nitrogen
hydrogen
selenium
sulfur
phosphorus
3. Metalloids share some of the properties of metals and some of the
properties of non-metals.
selenium
sulfur
phosphorus
Your body contains metals, non-metals, and metalloids. Some examples include iron, which helps release energy to your body cells, and potassium, which helps to maintain the fluid balance in your tissues.
Did you know ...
Hydrogen and helium are the most common elements in the universe. Stars are made almost entirely of these elements. The most common elements in the Earth’s crust are oxygen and silicon.
