Elements
- An element is a substance that cannot be broken down into any other substance. Every element is made up of its own type of atom. This is why the chemical elements are all very different from each other.
- Everything in the universe contains the atoms of at least one or more elements.
- The periodic table lists all the known elements and groups together those with similar properties.
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Table of Elements
- The periodic table (also known as the periodic table of elements) is organized so scientists can quickly discern the properties of individual elements such as their mass, electron number, electron configuration and their unique chemical properties.
Identifying Elements in the Table of Elements
- According to their Atomic Number
- Every element in the Table of Elements have their corresponding number of atoms. It is represented by the whole number shown in the top left corner of every element.
- As shown above, Lithium have 3 atomic number. This means that Lithium also have 3 protons. In neutral atoms the number of protons is also the same with the number of electrons. Any element with a different number of protons would be a different element.
- In a certain element, the atomic number shown is equivalent to the number of protons.
Determining the Mass Number of an Element
- For example, the mass number of Hydrogen shown below is 1.0078. We can round it off to a whole number of 1.
- To determine the mass number, you must add the number of protons and number of neutrons. In short you are adding the nucleons in an atom.
- Knowing the mass number and atomic number of an atom allows you to determine the number of neutrons present in that atom by SUBTRACTION.
Naming an Element
- The Mass Number (number of protons and neutrons) is represented by the letter A.
- The Atomic Symbol is represented by the letter X.
- The Atomic Number (number of protons in an atom) is represented by the letter Z.
General Chemistry 