University:
Ontario Tech University
Course:
CHEM1010U | Chemistry I
Academic year:

2024
Views:

51

Pages:

4
Author:

Avneet S.

Chemistry Lecture #2 1. Laws of Mass Conversion * Made before the atom was discovered * Nothing can be created or destroyed 2. Law of Definite Proportion * H₂O is always H₂O, no matter where you get water, the water particles of H and O is the same. * H₂O * Hydrogen: 1.0079 amu (mass of 1 H atom) * Oxygen: 15.999 amu (mass of 1 O atom) * Add amu values = 18.016 amu (1.0079 * 2 + 15.999) * % of Oxygen = 15.999 / 18.016 * 100 = 88.8% * % of Hydrogen = 1.0079 * 2 / 18.016 * 100 = 11.2% * Same proportion of Oxygen and Hydrogen in H₂O no matter what * If it doesn't have the same mass proportion, it's not H₂O. 3. Law of Multiple Proportions * NO and NO₂ * mass of N = 14 amu * mass of O = 16 amu * ratio of N in NO = 14/16 = 0.875 * ratio of N in NO₂ = 14/32 = 0.4375 * mass ratios aren't the same, less than 1, because of Oxygen Dalton's Atomic Theory * Three previous laws are used in Dalton's Theory: * 1. Law of Mass Conservation * 2. Law of Multiple Proportions * 3. Mass Conservation * 4. Mass Conservation * Discovery of the Electron Vid notes: * cathode ray; apply a magnet and the beam moves/repels; the charge is a (-) pole, beam charges repel, particles are two times smaller than hydrogen atoms * electron has a charge * smallest subatomic particle * thought to be the smallest thing * amount of repulsion depends on the field * Nucleus discovery * discovery of protons and neutrons, watch video? * protons and neutrons are approx. the same mass * atoms have mostly empty space, except in the nucleus * bring periodic table to lectures mass# = protons + neutrons mass# - protons = neutrons 30Zn30 30 protons = 30 electrons 30 neutrons 40Ca20 20 protons = 20 electrons 20 neutrons 36Kr36 36 protons = 36 electrons 36 neutrons Manganese, protons, electrons, neutrons: 54.9380 amu #protons = 25 #electrons = 25 #neutrons = 54.9380 - 25 = 29.9308 * Isotopes * Doc O. was using hydrogen isotopes * isotopes: same atom, different mass * mass on periodic table is the weighted isotopic average * based on percent abundance * same # of protons * different # of neutrons 12.011 amu (not the mass of an atom, not no atom has that mass)