Elements and Atoms

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Elements

Different basic substances with different properties are called elements.

Examples: Carbon (C), Oxygen (O), Gold (Au), Lead (Pb)

The atom is the smallest particle which retains the same properties of the element. It is extremely small. A carbon atom, for example, is 70 pm, or 7 x 10^-11 meters, in length.

In context: A single strand of hair is millions of atoms wide.

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Structure of an Atom

The proton is a positively charged subatomic particle which defines the element. The periodic table is listed in order of atomic number, or number of protons. Protons are located in the nucleus of an atom.

The neutron is also located in the nucleus of an atom. Neutrons carry no charge.

The electron is a negatively charged particle with a charge of equal magnitude to that of a proton. Electrons orbit the nucleus of an atom. The electron has a negligible mass.

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Notation

A <--------------------------Denotes the mass number, equal to Z + N (protons + neutrons)

X <-------------------------The Element's chemical symbol

Z <--------------------------Denotes the atomic number, or the number of protons

Example: Carbon-12 atom

6 neutrons (+ 6 p+)------> 12

Carbon atom----------------> C

6 protons--------------------> 6

Atoms of the same element with different amounts of neutrons are referred to as isotopes.

Below: Proton vs. Neutron vs. Electron