Counting Atoms in Compounds
A worksheet for Grade 11 Chemistry students focusing on understanding and applying rules for counting atoms in various chemical compounds, including those with subscripts and parentheses.
Includes
Standards
Counting Atoms in Compounds
Name:
Date:
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Read each question carefully and provide your answer in the space provided. Show all your work for calculations.
1. The small number written after an element symbol is called a , which indicates the number of atoms of that element in the compound.
2. When a chemical formula contains parentheses, the subscript outside the parentheses applies to inside the parentheses.
3. If no subscript is written after an element symbol, it is understood to be .
4. Explain how to count the total number of oxygen atoms in 2Al₂(SO₄)₃.
5. How many hydrogen atoms are in one molecule of H₂O?
1
2
3
4
6. What is the total number of atoms in one molecule of C₆H₁₂O₆?
18
24
30
36
Complete the table by counting the number of atoms for each element in the given chemical formula.
Chemical Formula
Element
Number of Atoms
Total Atoms
NaCl
Na
Cl
Ca(OH)₂
Ca
O
H
(NH₄)₃PO₄
N
H
P
O
7. A compound has the formula Fe₂(Cr₂O₇)₃. Determine the total number of atoms of each element present in this compound. Show your calculations.