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The Basics:
The study of chemistry is the study of matter (and the changes it undergoes. All matter is made up of atoms. Groups of atoms joined (bonded) together is called a molecule. In this section we are only looking at single atoms.
The current model of the atom is called the "Electron Cloud model" which is sometimes also referred to as the "Quantum Model."
The atom consists of two main regions: the nucleus and the electron cloud. Each of these regions has specific parts called subatomic particles (literally, sub=below/small, atomic= atom particle=parts, or small parts inside the atom). The nucleus has protons and neutrons. The electron cloud consists only of electron(s).
Subatomic particles also have charges:
(p+) protons = + charge Found in the nucleus
(n0) Neutrons = no charge Found in the nucleus
(e-) electrons = - charge Found in the electron cloud
A neutron walks into a juice bar and the bartender says to him "For you, no charge!"
Masses:
(p+) protons = 1 AMU (atomic mass unit)
(n0) Neutrons = 1 AMU (atomic mass unit)
(e-) electrons = negligible, do not contribute to mass
Atomic Number = # Protons
Mass Number = # Protons + # Neutrons
A group of atoms linked (we call this "bonded") together is called a molecule. Molecules can be two or more atoms of the same or different type of atoms. Carbon linked with a carbon, or maybe carbon linked with an oxygen - both are molecules!
A compound is two or more different atoms linked together. Which of the above would be a compound? Answer.
Quantum Model of the Atom means that the electron cloud is a probability of where a given electron might be at any time:
Why do we have to know this? Knowing the parts of an atom and it's notation (or shorthand) is critical because all chemical reactions involve mainly only electrons of the atom. The exception is nuclear chemistry (which we are unlikely to cover in this class), in which changes happen in the nucleus of the atom resulting in the atom's identity changing. Nuclear chemistry includes some pretty complicated math, and it deals with atoms decaying (breaking apart) into other atoms and some other pretty weird stuff. As for our day-to-day knowledge, atoms help shed light on why we don't mix things like bleach and ammonia and how the ingredients we use in food can either work together or be a problem in a recipe.
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