COUNT ATOM How to count atoms 2 H

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COUNT ATOM How to count atoms

COUNT ATOM How to count atoms

2 H 2 O COEFFICIENT SUBSCRIPT

2 H 2 O COEFFICIENT SUBSCRIPT

2 H 2 O The coefficient gets applied to the ENTIRE formula -this means

2 H 2 O The coefficient gets applied to the ENTIRE formula -this means that there are 2 molecules of water present! -you MULTIPLY this number by every subscript in the formula

2 H 2 O 2 MOLECULES!!!!

2 H 2 O 2 MOLECULES!!!!

2 H 2 O The subscript only gets applied to the element it follows

2 H 2 O The subscript only gets applied to the element it follows -If there is no subscript present, it is assumed that there is only 1 atom of that element in the molecule.

2 H 2 O How many hydrogen atoms are present? 4 How many oxygen

2 H 2 O How many hydrogen atoms are present? 4 How many oxygen atoms are present? 2

The easiest way to count atoms: 1. Write down all of the symbols for

The easiest way to count atoms: 1. Write down all of the symbols for all of the elements present in the formula 2. If there is a coefficient, write this number next to each of the symbols 3. Multiply the coefficient by the subscripts of each of the elements present in the formula

Let’s try an example: 4 Ca. CO 3

Let’s try an example: 4 Ca. CO 3

4 Ca. CO 3 Ca -1 x 4 = 4 C– 1 x 4=4

4 Ca. CO 3 Ca -1 x 4 = 4 C– 1 x 4=4 O – 4 x 3 = 12 This molecule has 4 -Ca, 4 -C, and 12 -O. The total number of atoms present is 12 + 4 = 20

3 CO 2

3 CO 2

3 CO 2 C– 3 x 1=3 O– 3 x 2=6 There are 3

3 CO 2 C– 3 x 1=3 O– 3 x 2=6 There are 3 – C, 6 – O. The total number of atoms is 6+3=9

2 C 6 H 12 O 6 GLUCOSE

2 C 6 H 12 O 6 GLUCOSE

2 C 6 H 12 O 6 C – 2 x 6 = 12

2 C 6 H 12 O 6 C – 2 x 6 = 12 H – 2 x 12 = 24 O – 2 x 6 = 12 The total number of atoms is 48

6 K 2 SO 4

6 K 2 SO 4

6 K 2 SO 4 K – 6 x 2 = 12 S– 6

6 K 2 SO 4 K – 6 x 2 = 12 S– 6 x 1=6 S– 6 x 1– 6 O – 6 x 4 = 24 Total number of atoms 48

Ca. Mg(CO 3)2

Ca. Mg(CO 3)2

Ca. Mg(CO 3)2 Ca – 1 Mg – 1 C– 1 x 2=2 O-

Ca. Mg(CO 3)2 Ca – 1 Mg – 1 C– 1 x 2=2 O- 3 x 2=6 Total number of atoms is 10

3 Pb(NO 3)2 Pb – 3 x 1 = 3 N– 3 x 1

3 Pb(NO 3)2 Pb – 3 x 1 = 3 N– 3 x 1 x 2=6 O – 3 x 2 = 18 Total number of atoms 27