Have you every wondered what the universe is made of?
No? Just me? Ok, cool.
One of the fundamental ideas of chemistry is the atom. The atom is the smallest unit of matter. Matter is made up of atoms and consists of every physical thing in the world (that we know of). In short, atoms make up everything.
Atoms are made of three primary components: electrons, protons, and neutrons.
Key concept
- Protons and neutrons are located in the nucleus of the atom.
- Electrons are located in the space around the nucleus.
Key Concept
- Protons are positively charged.
- Electron's are negatively charged.
- Neutrons are neutral or not charged.
The History of the Atom
John Dalton proposed a model for the atom in 1803. He suggested that the atom was a solid sphere. He also suggested that atoms of the same element are identical.
JJ Thomson discovered that the atom wasn't as solid as previously thought. His experiments with the cathode ray tube proved that atoms were made of smaller parts. This led to the discovery of the electron. JJ Thompson's model was called the plum pudding model. It was depicted as a sphere made of positively charged mass with electrons placed throughout it.
Ernest Rutherford later discovered that the nucleus of an atom was made of mostly empty space. He figured this out using the gold foil experiment.
The gold foil experiment used alpha particles to determine that atoms contain empty space. He fired alpha particles at an atom and found that most of them passed straight through. However, some bounced off of what was later determined to be the nucleus.
Neil Bohr suggested that electrons occupy specific energy levels around the nucleus of an atom. He found that these levels were discrete, meaning an electron can't just float around just anywhere. An electron can move between these levels, however they have to gain or loose energy to do it.
Bohr's model worked well for the hydrogen atom, but if falls short for many of the other atoms. Good attempt Bohr, but not quite.
Erwin Schrodinger showed that electrons behave like waves and particles. He did a lot of complex math to figure this out. His proposed model for the atom is called the electron cloud theory. This model suggests that electrons are likely to hang out in certain places around the nucleus. This model is the widely accepted model for an atom currently.
Last but not least, James Chadwick discovered the existence of the neutron. Seems kind strange right? Everyone was so focused on the electron that they didn't even consider the existence of a neutron? Either way, Chadwick discovered the neutron in 1932 (less than 100 years ago).
For more information about subatomic particles, check out my video below!
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