Protons, electrons, and the elements

Mass and charge of three elementary particlesThe building blocks of atoms are protons, electrons, and neutrons. The electron is the smallest and least massive, being 1/1,836 the mass of the proton. The proton and neutron have nearly the same mass. Read the text aloud
The electron and proton have exactly equal and opposite electric charges. The charge of the electron is −1.602×10−19 coulomb (C) and the charge on the proton is +1.602×10−19 C. The value e = 1.602×10−19 C is called the elementary charge and is represented by a lower-case e. Electric charge only occurs in multiples of the elementary charge. You can have a charge of −e, 0, e, 5e, or 1020e, but nature does not allow charges of 1.5e, −3.3e, or any noninteger multiple of the elementary charge. The neutron has zero electric charge but is important for another force, as we will see on page 1514. Read the text aloud Show Other elementary particles
All atoms of the same element have the same number of protons. Atoms of different elements contain different numbers of protons and electrons. For example, every atom of hydrogen has one proton and one electron. Every atom of helium has two protons and two electrons. The number of protons is called the atomic number. The atomic number of carbon is 6, telling you that every atom of carbon has six protons. The lightest element is hydrogen with 1 proton per atom and the heaviest naturally occurring element is uranium with 92 protons per atom.
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Periodic table is organized by the number of protons in each atom

A carbon atom has a net charge of zeroNeutral atoms contain an equal number of protons and electrons. For example, a carbon atom has six protons and six electrons. The elementary charge on the proton and electron are exactly the same, but opposite in sign, and so they cancel each other out and the total charge of an atom is exactly zero. Atoms are electrically neutral, which means that their net charge is zero. The reason we do not ordinarily feel electrical forces in the macroscopic world is not because matter does not contain charge, but because neutral atoms contain the same amount of positive and negative charges. Read the text aloud
A neutral oxygen-18 atom has eight protons and ten neutrons in its nucleus. How many electrons does it have? Show

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