Chemistry journey of atoms — 8-topic bundle

Everything you can see, touch, or even just weigh is matter. It has mass and takes up space. We categorize matter based on its composition.

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Atoms aren't just solid balls; they're built from even smaller pieces. The two main players we're focusing on today are protons and neutrons. Both are located in the atom's nucleus, which is the dense center.

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Neutrons are neutral particles, meaning they have no charge. They hang out with protons in the nucleus. While the number of protons defines the element, the number of neutrons can vary within atoms of the same element. These variations are called isotopes.

The mass number tells you the total count of both protons and neutrons in an atom's nucleus. It's called "mass number" because protons and neutrons are much heavier than electrons, so they account for almost all of an atom's mass.

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Ernest Rutherford's groundbreaking gold foil experiment in 1911 revealed that atoms have a tiny, dense, positively charged nucleus at their center, with electrons orbiting around it. This was a huge leap from the "plum pudding" model. However, his model had two major problems when viewed through the lens of classical physics:

You've learned that atoms aren't just tiny, indivisible balls. They have internal structure! Let's quickly recap the key players and what they mean for an atom.

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