# Chapter 2 - Rutherfords Model of the Atom atomic radius ~...

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atomic radius ~ 100 pm = 1 x 10 -10 m nuclear radius ~ 5 x 10 -3 pm = 5 x 10 -15 m Rutherford’s Model of the Atom If the atom is Florida Field (“Swamp”), then the nucleus is a marble on the 50-yard line. A nucleus is about 1 ten-trillionth of average atomic volume!

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mass p = mass n = 1840 x mass e -
Atomic number (Z) = number of protons in nucleus Mass number (A) = number of protons + number of neutrons = atomic number (Z) + number of neutrons Isotopes are atoms of the same element (X) with different numbers of neutrons in their nuclei X A Z H 1 1 H (D) 2 1 H (T) 3 1 U 235 92 U 238 92 Mass Number Atomic Number Element Symbol Atomic number, Mass number and Isotopes

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The Isotopes of Hydrogen
6 protons, 8 (14 - 6) neutrons, 6 electrons 6 protons, 7 (13 - 6) neutrons, 6 electrons How many protons, neutrons, and electrons are in C 14 6 ? How many protons, neutrons, and electrons are in C 13 6 ?

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Isotopic Abundance (%-abundance) = {[(number of atoms of a given isotope in the sample)] [(total # of atoms of all isotopes of that element in the sample)]} x 100% Example: 12 C is 98.89% of all naturally-occurring C 13 C is 1.11% of all naturally-occurring C 14 C is <0.01% of all naturally-occurring C
Period Group Alkali Metals Noble Gases Halogens Alkaline Earth Metals

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Dalton’s Atomic Theory (1808) 1. Elements are composed of extremely small particles called atoms . 2. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of all other elements. 3. Compounds are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction. 4. A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction.
2 Dalton’s Atomic Theory

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8 X 2 Y 16 X 8 Y +
A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical forces H 2 H 2 O NH 3 CH 4 A diatomic molecule contains only two atoms H 2 , N 2 , O 2 , Br 2 , HCl, CO A polyatomic molecule contains more than two atoms O 3 , H 2 O, NH 3 , CH 4

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A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance An empirical formula shows the simplest whole-number ratio of the atoms in a substance H 2 O H 2 O molecular empirical C 6 H 12 O 6 CH 2 O O 3 O N 2 H 4 NH 2

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Nomenclature of Binary Covalent Compounds Some have common names (H 2 O water, NH 3
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