Counting Atoms in Chemical Formulas

The video tutorial for eighth-grade science covers counting atoms in chemical formulas, focusing on linear formulas and formulas with parentheses. It explains how to identify and count atoms in compounds like NH4NO3 and CH3CH2Br, emphasizing the importance of adding and multiplying atoms based on their arrangement in the formula. The tutorial includes examples and models to aid understanding, preparing students for more advanced chemistry topics.

What is the main focus of today's science lesson?

• Learning about the periodic table

• Studying chemical reactions

• Reading comprehension

• Counting atoms in chemical formulas

In the formula NH4NO3, how many nitrogen atoms are present?

• One

• Three

• Four

• Two

When counting atoms in a linear formula, what should you remember to do?

• Only count the first element

• Ignore subscripts

• Add up all atoms of each type

• Count only the elements with subscripts

In the formula CH3CH2Br, how many hydrogen atoms are there?

• Three

• Six

• Four

• Five

What does a subscript outside parentheses in a chemical formula indicate?

• It only applies to elements outside the parentheses

• It applies to all elements inside the parentheses

• It is ignored

• It applies to only the first element inside

In the formula Al(NO3)3, how many nitrogen atoms are present?

• One

• Two

• Three

• Nine

How many oxygen atoms are in the formula Al(NO3)3?

• Three

• Six

• Nine

• Twelve

In the formula Co(NO3)2, how many cobalt atoms are there?

• Four

• Three

• Two

• One

How many nitrogen atoms are in Co(NO3)2?

• Four

• Three

• Two

• One

In Co(NO3)2, how many oxygen atoms are present?

• Three

• Six

• Nine

• Twelve