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Dive into the world of atomic structure, exploring the nature of protons, neutrons, and electrons. Learn why most alpha particles pass through matter and how nearly all atomic mass is concentrated in the nucleus, while the volume results from electrons. Understand isotopes, where elements share the same number of protons but differ in neutron count, affecting their atomic mass. This guide details atomic numbers, mass numbers, and the significance of molecular compounds. Perfect for students and enthusiasts looking to deepen their knowledge of chemistry.
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Neutral particles Negative particles Positive particles
Proton charge = +, mass = 1.0073 amu atomic mass units: 1amu = 1.6605402 x 10-24 g nucleus Neutron charge = neutral, mass = 1.0087 Electron charge = 1-, mass = 5.4586 x 10-4 amu Almost all the mass is in the nucleus, and almost all the volume is due to the electrons!
If this penny consisted of just nuclear material it would weigh……... One penny 190,000,000 TONS!!! Almost all the mass is in the nucleus, and almost all the volume is due to the electrons!
In a neutral atom, the number of (+) protons = the number of (-) electrons And.. The number of protons is equal to the atomic number of the element. Since the mass of an atom is almost entirely located in the nucleus, the mass number is equal to: the number of protons PLUS the number of neutrons
The lower numbers found on most periodic tables are the ATOMIC MASSES (WEIGHTS) NOT the ATOMIC MASS NUMBER!
Isotopes: same element, different atomic mass. How can this be?
Isotopes: same element, different atomic mass. How can this be? If it’s the same element , the number of protons can’t change. So what must change? Isotopes: same element, different number of neutrons.
ISOTOPES 13C 14C 11C 12C 6 6 6 6 No. protons: No. Electrons: No. neutrons: 6 6 6 6 6 8 7 5
ISOTOPES OF NITROGEN 0.37% 15.0001 amu 99.63% 14.0031 amu
Atomic mass or weight: the weighted average of the atomic masses of all naturally occurring isotopes present. Atomic # Atomic mass or weight Naturally occurring ISOTOPES: 75.53% x 0.7553 = 26.412 34.9689 amu 36.9659 amu x 0.2447 = 9.045 24.47% Atomic mass on periodic table 35.45
Boy there are a lot of losers! “Losers” Metals lose e-’s in chemical reactions
metalloids: non-metals: gain electrons (or share)
periods 1 periods 2 3 4 5 6 7
Groups or families 1 2 3 4 5 6 7
Molecular Compounds: (molecules) H2O CO2 CO CH4 H2O2 O2 C2H4 O3
7 diatomic elements 6 + 1 = 7
Molecular and Empirical Formulas: Simplest Form Actual formula molecular or empirical? butene: C4H8 CH2 What is the empirical formula? Carbon dioxide: CO2 empirical or molecular?
Ions and ionic compounds: cation: positive charge (lost e-’s) Na+ 11 protons and only 10 electrons anion: negative charge (extra e-’s) 17 protons and 18 electrons Cl -