 Reviewing Subatomic Particles

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Reviewing Subatomic Particles
Nucleus contains: 1. Protons - 2. Neutrons - Positively charged, mass of 1 amu No charge, mass of 1 amu Electrons - Negatively charged, mass of 1/1840 amu Atomic number = # of Protons = # of Electrons Mass Number = # of protons + # of neutrons

Distinguishing Between Atoms
Atomic Number (Z) – The number of protons in the nucleus of the atom. In a neutral atom the # of protons (+) = the # of electrons (-) Nuclear Charge = # of protons

The Nucleus Protons (positive charge) Neutrons (No Charge)
Electrons (negative charge) are found in a cloud outside of the nucleus.

Mass Number (A) = number of protons + the number of neutrons
Most of the mass of an atom is found in the nucleus. The mass number is given after the name of the element (example: Carbon – 12) Isotope – Atoms that have the same number of protons but different numbers of neutrons. Example: Carbon – 12 and Carbon – 14

U Atomic Symbols 238 92 Mass Number = protons + neutrons
Ion Charge (if there is one) Symbol = Element Atomic Number = Protons

Atomic Masses Atomic Mass Unit (AMU) – Using carbon-12 as a base unit, the mass is defined as 1/12 the mass of the carbon-12 isotope. mass of a proton = 1 amu mass of a neutron = 1 amu. Atomic Mass – The weighted average mass of the isotopes of an element.

How to Calculate the Average Atomic Mass
Change the percentages back to the decimal values Example: % = .9994 Multiply the mass number by the decimal of the percent. Example: Carbon – 12 (.9994 x 12) Add all of the products of the mass numbers and the decimal percentages