Learn: What an element is, and why elements are listed in the periodic table

Welcome!I've reviewed your growth area, and this lesson will help you understand what an element is and why elements are organised in the periodic table. Let's get started!

What is an element?An element is a substance made up of only one type of atom. Each element is defined by the number of protons in its nucleus, called the atomic number.For example, hydrogen has 1 proton, so it is element 1. Oxygen has 8 protons, so it is element 8.

Why are elements listed in the periodic table?The periodic table arranges all known elements in order of their atomic number. This arrangement helps scientists predict the properties of elements based on their position in the table.Elements are grouped together in columns, called groups, because they share similar chemical properties. For example, Group 1 elements are very reactive metals, like sodium and potassium.

How is the periodic table organised?The periodic table has periods (horizontal rows) and groups (vertical columns). As you move across a period, the number of protons increases, and the properties of the elements change.Groups contain elements with similar properties because they have the same number of electrons in their outer shell.

What are isotopes?Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means they have the same atomic number but different mass numbers.For example, carbon-12 has 6 protons and 6 neutrons, while carbon-14 has 6 protons and 8 neutrons.

Review Time!Great work! You've learned about elements, isotopes, and the periodic table. Let's test your understanding with a few questions.