Counting Atoms in Chemical Formulas

Miss Jack introduces counting atoms using chemical formulas, starting with H2O. She explains the EA chart method, which involves listing elements and their subscripts. The video covers counting atoms in simple formulas like H2O and CH4, and progresses to more complex formulas like Al2(SO4)3 and Sr3(PO4)2, demonstrating how to handle parentheses and coefficients. The tutorial emphasizes understanding chemical symbols, subscripts, and the importance of multiplication in formulas with parentheses.

What does the EA chart help us identify in a chemical formula?

• The temperature at which the reaction occurs

• The elements and the number of each atom

• The physical state of the elements

• The time it takes for a reaction to complete

Tags

NGSS.MS-PS1-1

How many total elements are present in 'H2O'?

• 4

• 1

• 2

• 3

Tags

NGSS.MS-PS1-1

If an element symbol in a chemical formula has no subscript, how many atoms of that element are present?

• Zero

• One

• Two

• It varies

In the formula 'H2O', what does the '2' represent?

• Two oxygen atoms

• Two hydrogen molecules

• Two molecules of water

• Two hydrogen atoms

Tags

NGSS.MS-PS1-1

What does a subscript in a chemical formula indicate?

• The number of molecules

• The charge of the atom

• The number of atoms of the element

• The atomic mass of the element

In a chemical formula, what does a capital letter signify?

• A new element

• A mixture

• A reaction

• A compound

How do you handle parentheses in chemical formulas?

• Divide the subscript inside by the number outside

• Add the number outside to the subscript inside

• Multiply the subscript inside by the number outside

• Ignore them

In the formula 'Al2(SO4)3', how many atoms of sulfur are there?

• 6

• 9

• 3

• 2

Tags

NGSS.MS-PS1-1

What should you do if a chemical formula starts with a coefficient?

• Add the coefficient to each subscript

• Subtract the coefficient from each subscript

• Ignore the coefficient

• Multiply all atoms by the coefficient

What is the total number of atoms in the formula 'Sr3(PO4)2' after considering the coefficient?

• 13

• 11

• 8

• 26

Tags

NGSS.MS-PS1-1