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11 Dec 2025

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2 pages

Understanding Atomic and Mass Numbers, Isotopes, and Ions

RiceFarmer

@ricefarmer_jhrs

Ever wondered what makes each element unique on the periodic... Show more

Atomic and Mass Numbers

Understanding atoms is like cracking a secret code that's written right on the periodic table. Every element has two crucial numbers that tell you exactly what's happening inside its atoms.

The atomic number is the smaller number you'll see on each element. This number is absolutely vital because it tells you how many protons and electrons are in a normal atom of that element. For instance, lithium has an atomic number of 3, which means every lithium atom contains exactly 3 protons and 3 electrons.

The mass number is the larger number, and it reveals the total count of protons and neutrons combined. Since lithium's mass number is 7 and it has 3 protons, you can work out that it must have 4 neutrons. The simple trick is: neutrons = mass number - atomic number.

Isotopes are like different versions of the same element. They have identical numbers of protons and electrons, but different numbers of neutrons. This means isotopes of the same element behave chemically the same way, but have different masses.

Quick Check: Try finding the protons, neutrons, and electrons for magnesium (Mg), calcium (Ca), and potassium (K) using a periodic table!

Ions

Sometimes atoms don't play by the usual rules - they can gain or lose electrons and become charged particles called ions. This happens when atoms want to become more stable, and it's absolutely crucial for understanding how elements bond together.

Positive ions form when an atom loses one or more electrons. Since electrons carry negative charge, losing them leaves the atom with more positive protons than negative electrons, creating an overall positive charge.

Negative ions work the opposite way - they form when atoms gain extra electrons. Now there are more negatively charged electrons than positive protons, giving the ion an overall negative charge.

Remember, ions still keep the same number of protons (that never changes for an element), but their electron count is different from a neutral atom. This charge difference is what makes ions so reactive and important in forming compounds.

Remember: Protons never change - only electrons can be gained or lost to form ions!

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11 Dec 2025

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2 pages

Understanding Atomic and Mass Numbers, Isotopes, and Ions

RiceFarmer

@ricefarmer_jhrs

Ever wondered what makes each element unique on the periodic table? It's all about the tiny particles inside atoms - protons, neutrons, and electrons - and how they can change to create different versions of the same element or give... Show more

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Atomic and Mass Numbers

Understanding atoms is like cracking a secret code that's written right on the periodic table. Every element has two crucial numbers that tell you exactly what's happening inside its atoms.

Quick Check: Try finding the protons, neutrons, and electrons for magnesium (Mg), calcium (Ca), and potassium (K) using a periodic table!

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Ions

Negative ions work the opposite way - they form when atoms gain extra electrons. Now there are more negatively charged electrons than positive protons, giving the ion an overall negative charge.

Remember: Protons never change - only electrons can be gained or lost to form ions!