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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.

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Presentation on theme: "Reviewing Subatomic Particles Nucleus contains: 1. Protons - 2. Neutrons - Positively charged, mass of 1 amu No charge, mass of 1 amu Electrons - Negatively."— Presentation transcript:

1 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

2 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

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

4 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

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

6 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.

7 How to Calculate the Average Atomic Mass 1. Change the percentages back to the decimal values –Example: 99.94% = Multiply the mass number by the decimal of the percent. –Example: Carbon – 12 (.9994 x 12) 3. Add all of the products of the mass numbers and the decimal percentages


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