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Chapter 8 Atoms and Periodic Properties: Notes

# Chapter 8 Atoms and Periodic Properties: Notes -...

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waveChapter 8 Atoms and Periodic Properties Notes Key Terms: 1. atomic mass unit – It is impossible to find the mass of a given atom. In order to compare the mass of one atom to another you compare the mass of any atom to the mass of an atom of a particular isotope of carbon. This isotope is assigned a mass of 12.00 units called atomic mass units (u). The isotope is called carbon-12 and provides a standard to which the masses of all other isotopes are compared. Relative mass of any isotope is based on the mass of a carbon-12 isotope. 2. atomic number – The number of protons in the nucleus of an atom is called the atomic number. All of the atoms of a particular element have the same number of protons in their nuclei, so all atoms of an element have the same atomic number. 3. atomic weight – Elements occur in nature as a mixture of isotopes, and the contribution of each is calculated in the atomic weight. Atomic weight is an average of the isotopes based on their mass compared to carbon-12 and their relative abundance in nature. The fractional part of occurrence is multiplied by the relative atomic mass for each isotope and the results summed to obtain the atomic weight. 4. Balmer series – 1885 Swiss mathematics teacher named J.J. Balmer was studying the regularity of spacing of the hydrogen line spectra. He was able to develop an equation that fit all the visible lines. Violet line, Violet line, Blue-green line, and Red line. These four lines became known as the Balmer series. 5. Electron – Discovered by J.J. Thomson in 1897 while doing experiments on cathode rays. Thomson found that the charge-to-mass ration was the same no matter what gas was in the tube or of what materials the electrodes were made. He had discovered the electron, a fundamental particle of matter and one of the building blocks of an atom. 6. electron dot notation – Outer orbital electrons, the highest energy level electrons, are conveniently represented with an electron dot notation. This is made by writing the chemical symbol with dots around it indicating the number of outer orbital electrons. 7.

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Chapter 8 Atoms and Periodic Properties: Notes -...

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