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Learn: Formulae of elements, compounds and ions
Edexcel GCSE Chemistry
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Welcome!Today, we'll learn about the formulae of elements, compounds, and ions. This topic is essential for understanding chemical reactions and equations.
What are chemical formulae?A chemical formula shows the types and numbers of atoms in a substance. For example, H2O represents water, with two hydrogen atoms and one oxygen atom.
Elements and their symbolsEvery element has a unique symbol, usually one or two letters. For example, Na stands for sodium, and Cl stands for chlorine. These symbols are listed in the periodic table.
Quick check: What is the correct chemical symbol for oxygen?
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Compounds and their formulaeA compound is made of two or more elements chemically bonded together. Its formula shows the ratio of each element's atoms. For example, CO2 represents carbon dioxide, with one carbon atom and two oxygen atoms.
The formula for water is {{blank0}}. It contains {{blank1}} hydrogen atoms and one oxygen atom.
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Ions and their formulaeAn ion is a charged particle formed when atoms lose or gain electrons. The formula of an ion includes its charge, such as Na+ for a sodium ion or Cl- for a chloride ion.
Match the items on the left with their correct pairs on the right
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Balancing ionic chargesWhen forming compounds, the total positive and negative charges must balance. For example, in NaCl, one Na+ balances one Cl-.
Which of the following are correct ionic formulas? (Select all that apply)
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Review Time!Great work! We've covered chemical formulae for elements, compounds, and ions. Let's test your understanding with a few final questions.
Which of the following represents a compound?
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The formula for sodium chloride is {{blank0}}.
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Match the items on the left with their correct pairs on the right
Start the lesson to answer this matching question
Match the items on the left with their correct pairs on the right
Start the lesson to answer this math equation question
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