Atoms are the fundamental building blocks of everything around us....
Chemistry56 views·Updated Jun 10, 2026·3 pagesUnderstanding the Atom: Structure and Its Parts
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The Structure of the Atom
Atoms are the smallest particles of an element that maintain the element's properties. Each atom has a central nucleus containing protons and neutrons, surrounded by orbitals where electrons move around.
The three main subatomic particles each play a crucial role. Protons carry a positive charge and live in the nucleus. Electrons, with their negative charge, orbit in the regions around the nucleus. Neutrons have no charge and reside alongside protons in the nucleus.
The arrangement and number of these particles determine what element an atom is. This is why carbon behaves differently from oxygen or gold - they have different particle counts and arrangements.
Quick Fact: Scientists measure atomic particles using the atomic mass unit (amu), which equals 1/12 the mass of a carbon-12 atom or about 1.66 × 10^-24 grams. That's incredibly tiny!
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The Size of Subatomic Particles
Subatomic particles have mind-blowingly small masses. Both protons and neutrons weigh approximately 1 amu , while electrons are roughly 1,800 times lighter at 9.109 × 10^-28 grams.
The atomic number (Z) tells you how many protons an atom has and identifies the element. Every atom of hydrogen has 1 proton, while every atom of oxygen has 8 protons. This number increases as you move across the periodic table.
The mass number (A) represents the total number of protons and neutrons in an atom's nucleus. Atoms of the same element with different mass numbers are called isotopes. For example, carbon-12 and carbon-14 are isotopes of carbon with 6 protons but different neutron counts.
Remember This: While all atoms of an element must have the same number of protons, they can have different numbers of neutrons, creating different isotopes of the same element.
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Atomic Mass
The atomic mass of a single atom is approximately equal to the combined mass of its protons and neutrons. Since electrons are so tiny, their mass is usually considered negligible in these calculations.
Elements in nature typically exist as mixtures of isotopes. The average atomic mass you see on the periodic table is a weighted average that accounts for all naturally occurring isotopes of an element and their relative abundance.
To calculate average atomic mass, you multiply each isotope's mass by its fractional abundance (percentage in decimal form) and then add these values together. The formula looks like:
Study Tip: When working with isotopes, pay attention to both the mass number and the natural abundance. The isotope with the highest abundance contributes most to the element's average atomic mass.
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Chemistry56 views·Updated Jun 10, 2026·3 pagesUnderstanding the Atom: Structure and Its Parts
Atoms are the fundamental building blocks of everything around us. These tiny particles define elements and have unique structures that determine their properties. Understanding atoms helps explain how all matter in our universe behaves.
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The Structure of the Atom
Atoms are the smallest particles of an element that maintain the element's properties. Each atom has a central nucleus containing protons and neutrons, surrounded by orbitals where electrons move around.
The three main subatomic particles each play a crucial role. Protons carry a positive charge and live in the nucleus. Electrons, with their negative charge, orbit in the regions around the nucleus. Neutrons have no charge and reside alongside protons in the nucleus.
The arrangement and number of these particles determine what element an atom is. This is why carbon behaves differently from oxygen or gold - they have different particle counts and arrangements.
Quick Fact: Scientists measure atomic particles using the atomic mass unit (amu), which equals 1/12 the mass of a carbon-12 atom or about 1.66 × 10^-24 grams. That's incredibly tiny!
2
of 3Sign up to see the content. It's free!
- Access to all documents
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- Join milions of students
The Size of Subatomic Particles
Subatomic particles have mind-blowingly small masses. Both protons and neutrons weigh approximately 1 amu , while electrons are roughly 1,800 times lighter at 9.109 × 10^-28 grams.
The atomic number (Z) tells you how many protons an atom has and identifies the element. Every atom of hydrogen has 1 proton, while every atom of oxygen has 8 protons. This number increases as you move across the periodic table.
The mass number (A) represents the total number of protons and neutrons in an atom's nucleus. Atoms of the same element with different mass numbers are called isotopes. For example, carbon-12 and carbon-14 are isotopes of carbon with 6 protons but different neutron counts.
Remember This: While all atoms of an element must have the same number of protons, they can have different numbers of neutrons, creating different isotopes of the same element.
3
of 3Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
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Atomic Mass
The atomic mass of a single atom is approximately equal to the combined mass of its protons and neutrons. Since electrons are so tiny, their mass is usually considered negligible in these calculations.
Elements in nature typically exist as mixtures of isotopes. The average atomic mass you see on the periodic table is a weighted average that accounts for all naturally occurring isotopes of an element and their relative abundance.
To calculate average atomic mass, you multiply each isotope's mass by its fractional abundance (percentage in decimal form) and then add these values together. The formula looks like:
Study Tip: When working with isotopes, pay attention to both the mass number and the natural abundance. The isotope with the highest abundance contributes most to the element's average atomic mass.
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What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Similar Content
Most popular content in Chemistry
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Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user