Chemistry Examples

H g

$H g$

Step 1

Find the element

Hg

$Hg$ on the periodic table.

80	Atomic Number
Hg	Element Symbol
Mercury	Element Name
200.59	Average Atomic Mass

Step 2

The atomic weight is a measurement of the total number of particles in an atom's nucleus including both protons and neutrons. So the first step is to locate the atomic mass on the periodic table, and round the value to the nearest whole number.

200.59

$200.59$ round to

201

$201$

Step 3

The mass number is the number of particles in an atom's nucleus. The nucleus is made up of protons and neutrons.

Atomic Mass = Number of Protons + Number of Neutrons

$Atomic Mass = Number of Protons + Number of Neutrons$

Step 4

Find the element

Hg

$Hg$ on the periodic table.

80	Atomic Number
Hg	Element Symbol
Mercury	Element Name
200.59	Average Atomic Mass

Step 5

To find the number of protons in

mercury

$mercury$ , first locate the element on the periodic table. Next, find the atomic number which is located above the element's symbol. Since

mercury

$mercury$ 's atomic number is

80

$80$ ,

Hg

$Hg$ has

80

$80$ protons.

80

$80$ protons

Step 6

Fill in the known values where

N

$N$ represents the number of neutrons.

201 = 80 + N

$201 = 80 + N$

Step 7

Rewrite the equation as

80 + N = 201

$80 + N = 201$ .

80 + N = 201

$80 + N = 201$

Step 8

Move all terms not containing

N

$N$ to the right side of the equation.

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Step 8.1

Subtract

80

$80$ from both sides of the equation.

N = 201 - 80

$N = 201 - 80$

Step 8.2

Subtract

80

$80$ from

201

$201$ .

N = 121

$N = 121$

N = 121

$N = 121$

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