Counting Atoms Worksheet

1. Chemical formulas can have three components. a) The ____________ which are represented by a single uppercase letter, or represented by an uppercase letter followed by a lowercase letter. This tells you the types of elements in the compound.

• element symbols

• chemical bonds

• atomic numbers

• molecular weights

Answer explanation

Tags

NGSS.MS-PS1-1

Chemical formulas can have three components. The ____________ which are numbers that are found on the lower ________________ - hand side of each element symbol. This tells you the number of ____________ of this element in the molecule. If an element symbol has no subscript next to it, then this indicates that there is only ____________ atom of this element in the molecule.

• subscripts, right, atoms, one

• coefficients, left, molecules, two

• prefixes, upper, ions, three

• indices, center, electrons, four

Tags

NGSS.MS-PS1-1

The ____________ which surround some groups of atoms indicate that the numbers of all of the atoms inside the bracket need to be ____________ by the ____________ on the outside of the bracket found on the lower ________________ - hand side of that bracket.

• brackets, multiplied, subscript, right

• parentheses, divided, superscript, left

• braces, added, coefficient, upper

• quotes, subtracted, exponent, middle

Record the number of each atom in each molecule, then record the total number of atoms in the molecule: 1) NaOH

• Na: 1, O: 1, H: 1, Total: 3

• Na: 2, O: 1, H: 1, Total: 4

• Na: 1, O: 2, H: 1, Total: 4

• Na: 1, O: 1, H: 2, Total: 4

Tags

NGSS.MS-PS1-1

Record the number of each atom in each molecule, then record the total number of atoms in the molecule: 2) HNO₃ Element | # of Atoms ________ | __________ ________ | __________ ________ | __________ Total: __________

• H: 1, N: 1, O: 3, Total: 5

• H: 2, N: 1, O: 2, Total: 5

• H: 1, N: 2, O: 3, Total: 6

• H: 1, N: 1, O: 2, Total: 4

Tags

NGSS.MS-PS1-1

Record the number of each atom in each molecule, then record the total number of atoms in the molecule: 3) Li₂O Element | # of Atoms ________ | __________ ________ | __________ Total: __________

• Li: 2, O: 1, Total: 3

• Li: 1, O: 2, Total: 3

• Li: 2, O: 2, Total: 4

• Li: 1, O: 1, Total: 2

Tags

NGSS.MS-PS1-1

Record the number of each atom in each molecule, then record the total number of atoms in the molecule: 4) Li₂SO₄ Element | # of Atoms ________ | __________ ________ | __________ ________ | __________ Total: __________

• Li: 2, S: 1, O: 4, Total: 7

• Li: 1, S: 2, O: 4, Total: 7

• Li: 2, S: 1, O: 2, Total: 5

• Li: 2, S: 2, O: 4, Total: 8

Tags

NGSS.MS-PS1-1

Record the number of each atom in each molecule, then record the total number of atoms in the molecule: 5) NH₄Cl Element | # of Atoms ________ | __________ ________ | __________ Total: __________

• N: 1, H: 4, Cl: 1, Total: 6

• N: 2, H: 4, Cl: 1, Total: 7

• N: 1, H: 3, Cl: 2, Total: 6

• N: 1, H: 4, Cl: 2, Total: 7

Tags

NGSS.MS-PS1-1

Record the number of each atom in each molecule, then record the total number of atoms in the molecule: 6) CaClO₃ Element | # of Atoms ________ | __________ ________ | __________ ________ | __________ Total: __________

• Ca: 1, Cl: 1, O: 3, Total: 5

• Ca: 1, Cl: 3, O: 1, Total: 5

• Ca: 3, Cl: 1, O: 3, Total: 7

• Ca: 1, Cl: 1, O: 2, Total: 4

Tags

NGSS.MS-PS1-1

Record the number of each atom in each molecule, then record the total number of atoms in the molecule: 7) H₂COCH₂

• H: 4, C: 2, O: 1, Total: 7

• H: 2, C: 2, O: 2, Total: 6

• H: 6, C: 1, O: 1, Total: 8

• H: 4, C: 1, O: 2, Total: 7

Tags

NGSS.MS-PS1-1