Atomic number, mass number, and isotopes - Khan Academy
Each atom has a charged sub-structure consisting of a nucleus, which is made of protons and neutrons, surrounded by electrons. The number of protons and the mass number of an atom define the type of atom. Atoms of the same element …
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The sum of the number of neutrons and protons in an atom is called its mass number. If we know the mass number of an atom, we can determine the number of neutrons in its nucleus.
Elements and atomic number - Khan Academy
An element is defined by the number of protons in its atoms, known as its atomic number. The periodic table organizes the elements by atomic number and provides other key information about them such as their names and chemical symbols.
Atomic number, atomic mass, and isotopes (article) | Khan Academy
A property closely related to an atom’s mass number is its atomic mass. The atomic mass of a single atom is simply its total mass and is typically expressed in atomic mass units or amu. By definition, an atom of carbon with six neutrons, carbon-12, has an atomic mass of 12 amu.
Atomic number and mass number (practice) | Khan Academy
Let's solve some problems to better understand atomic and mass numbers. Skip to main content If you're seeing this message, it means we're having trouble loading external resources on our …
Average atomic mass - Khan Academy
The average atomic mass (sometimes called atomic weight) of an element is the weighted average mass of the atoms in a naturally occurring sample of the element. Average masses are generally expressed in unified atomic mass units (u), where 1 u is equal to exactly one-twelfth the mass of a neutral atom of carbon-12.
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The webpage provides a lesson on average atomic mass in chemistry.
The mole and Avogadro's number (video) | Khan Academy
One mole of a substance is equal to 6.022 × 10²³ units of that substance (such as atoms, molecules, or ions). The number 6.022 × 10²³ is known as Avogadro's number or Avogadro's constant. The concept of the mole can be used to convert between mass and number of particles.
Atomic nucleus - Khan Academy
And then it has its atomic mass number, is the number of protons plus the number of neutrons. And do the neutrons in gray, right? So when it experiences alpha decay, what happens to the element?
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Protons and neutrons are found in the nucleus, the dense region at the center of an atom. Electrons are found outside the nucleus. Protons are positively charged and have a mass of about 1 u. Neutrons are neutral (have no charge) and also have a mass of about 1 u. Electrons are negatively charged and have a much smaller mass of about 0.0005 u.