Counting Atoms in Chemical Formulas

The video tutorial covers counting atoms in chemical formulas, focusing on linear formulas and those with parentheses. It provides examples like NH4NO3, CH3CH2Br, Al(NO3)3, and Co(NO3)2, explaining how to count atoms by adding or multiplying based on the formula structure. The tutorial emphasizes understanding the concept of groups in formulas with parentheses and prepares students for guided practice.

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

• Newton's laws of motion

• Counting atoms in chemical formulas

• Photosynthesis process

• The water cycle

In a linear formula, how do you determine the number of atoms of an element?

• By multiplying the atomic number by the subscript

• By counting the number of times the element appears

• By adding up all the subscripts of the element

• By looking at the color of the element

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

• Four

• Three

• Two

• One

What is the total number of hydrogen atoms in the formula CH3CH2Br?

• Four

• Six

• Five

• Three

When dealing with formulas with parentheses, what does the subscript outside the parentheses indicate?

• The number of molecules

• The number of atoms outside the parentheses

• The atomic mass of the compound

• The number of groups of atoms inside the parentheses

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

• Six

• Nine

• Three

• One

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

• Three

• Six

• Nine

• Twelve

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

• Four

• Three

• Two

• One

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

• Three

• One

• Four

• Two

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

• Three

• Four

• Nine

• Six