How many Atoms in a Penny are there?

According to the United Nations member state list, there are approximately 180 recognized currencies in the world that circulate in about 197 countries. However, today, we will talk about the penny. The term penny is not just for the denomination of a currency in the United States because various other nations also use it. But have you ever wondered how many atoms in a penny are there? Let us know more about what are the reams of copper atoms in a penny and how many electrons does a penny have.

1. What is a Penny?

It is the smallest denomination in the currency system and exists in the form of a coin. The term penny was borrowed from the Carolingian denarius. The earliest version was minted of 0.940 fine silver and weighed about 1/240 pounds. However, in the coming years after the wars, the minting material shifted from silver to base materials. (See Origin of Dollar Sign)

2. What is the Material of a Penny?

During the Napoleonic Wars (1802-1815) pennies were minted from copper. 24 pennies were minted from 1 lb. (453.6 grams) of copper. However, after the wars considering the falling economy, the copper pennies were replaced by bronze pennies. Moreover, 48 pennies could be minted from 1 lb. of bronze. (See Why are Dimes Smaller than Pennies?)

3. What are the Dimensions and Weight of a Penny?

You are moving close to finding out how many atoms in a penny are there. The weight of a penny is expressed in unit grains which is a measuring unit of mass and 1 grain is equal to 64.79891 milligrams. This mass is about the weight of a single grain of cereal. Other units to express the weight are troy and troy pound. 

• The diameter of a penny is 13.05 millimeters (0.75 inches).
• The thickness of a penny is 1.52 millimeters (0.0598 inches).
• Weight after the last alteration made in 1982 is about 2.5 grams (0.08 troy pounds).

4. How many Dozens of Copper are in a Penny?

One Cu penny has 3.0 × 10²² Cu atoms. Since dozen of any quantity refers to 12 counts, we can say that one dozen of Cu has 12 atoms. Considering this value, we can find out how many dozens are there in 3.0 × 10²² Cu atoms

(3.0 × 10²²)/12 atoms = 2.5 × 10²¹ dozen.

5. How many Gross of Copper is in a Penny?

One Cu penny consists of 3.0 × 10²² Cu atoms. Since the gross of any quantity refers to 144 counts, one gross of Cu has 144 atoms. Here also we will be using the same equation as we did in the dozen part.

(3.0 × 10²²)/144 atoms = 2.1 × 10²⁰ gross. 

6. How many Reams of Copper Atoms in a Penny are there?

One Cu penny is made up of 3.0 × 10²² Cu atoms. Since the ream of any quantity refers to 500 counts, we can say that one ream of Cu has 500 atoms. Here we will be using the same equation as we did in the dozen part. Let’s consider the following relationship as the conversion factor.

(3.0 × 10²²)/500 atoms = 6 × 10¹⁹ reams. Must read How many Nickels are in a Dollar?

7. How many Atoms in a Penny are there?

The mass of a new penny is 2.5 g. A penny contains 0.037282 moles of zinc and 0.00098354 moles of copper.

In the overall percentage form, it has the composition of 95% copper, 4% tin, and 1% zinc. According to the United States minted penny, a penny is made of 97.50% zinc and 2.50% copper which means the amount of zinc and copper in grams can be calculated as follows:

Further, with this, we get to know that,

• The mass of Zn in the penny is 2.500 g × 97.5% = 2.500 g × 0.975 = 2.4375 g zinc.
• The mass of Cu in the penny  is 2.500 g × 2.5% = 2.500 g × 0.025 = 0.0625 g copper

Considering molar mass,

• Zinc – 65.380 grams per mole
• Copper – 63.546 grams mole

Now, to calculate how many atoms in a penny are there, let’s find the respective number of atoms:

• No. of Zn atoms = 2.4375 g Zn × ( 1 mol / 65.38 g) × (6.023 × 10²³ atoms / 1 mol) = 2.24 × 10²² Zn atoms
• No. of Cu atoms = 0.0625 g Cu × ( 1 mol / 63.546 g) × (6.023 × 10²³ atoms / 1 mol) = 5.9 × 10²⁰ Cu atoms 

The sum is 5.9 × 10²⁰ + 2.24 × 10²² = 0.059 × 10²² + 2.24 × 10²² = 2.299 × 10²² ≈ 2.30 × 10²²

Finally, the answer to your question: how many atoms in a penny are there?  is 2.30 × 10²² atoms. 

Here, 6.023 × 10²³ atoms is Avogadro’s constant. (See How many valence electrons does oxygen have?)

8. How many Electrons does a Penny Have?

After getting to know about how many atoms in a penny are there, it will be interesting to learn how many electrons are there in a penny. Before reaching the end result, we will move through the following calculations.

Now, we will assume that a penny is mostly composed of copper and we are considering an example of an old Cu penny, 

• The molar mass of copper is 63.55 grams per mol, represented by W
• The total mass of an older penny is 3.11 grams, represented by w

The number of moles of copper in the copper penny will be,

• Moles = w / W
• Or, 3.11 grams / 63.55 grams per mole, 
• Moles = 4.89 × 10^-2 mol

Now we will move toward electrons with the next step. 1 atom of copper contains 29 electrons.

The number of electrons present in 1 mol of copper is,

• = 29 electrons per atom × 6.023 × 10²³ atoms/ mol, [6.023 × 10²³ atoms is Avogadro’s number]
• = 174.667 × 10²³ electrons per mol.

Therefore, the total number of electrons present in the 4.89 × 10^-2 mol of copper is:

• Electrons = 4.89 × 10^-2 mol × 174.667 × 10²³ electrons per mol
• Electron = 854.1212 × 10²¹ electrons

This means that there is a total of 854.1212 × 10²¹ electrons in a copper penny. (See How many Electrons can a Carbon Atom share?)

9. Which Country uses Penny as a Currency?

You may have heard about the penny as a denomination in the United States. However, this is not the only country to use the penny. Here is a list of all the countries that are presently using a penny.

• Bosnia and Herzegovina as pfennig
• Falkland Islands as Falkland Island penny
• Gibraltar as Gibraltar penny
• Guernsey as a Guernsey pound
• Ireland as euro cent
• Isle of Man as Manx penny
• Jersey as Jersey penny
• Saint Helena and Ascension Island as Saint Helena penny
• United Kingdom as the British pound
• United States as a cent

So, with this, you learned about how many atoms in a penny are there. And before that, you got to know about the reams of copper atoms in a penny. Now trick your friends by asking them how many electrons does a penny have? Do not forget to share this with a chemistry student. By the way, which currency do you use? (See How much is 6 Million Pennies?)