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- https://phys.libretexts.org/Courses/Coalinga_College/Physical_Science_for_Educators_(CID%3A_PHYS_14)/03%3A_Atomic_Theory_and_Periodic_Table/3.02%3A_Atoms_and_the_Periodic_Table/3.2.07%3A_Atomic_Mass_and_Atomic_NumberAtoms are the fundamental building blocks of all matter and are composed of protons, neutrons, and electrons. Because atoms are electrically neutral, the number of positively charged protons must be e...Atoms are the fundamental building blocks of all matter and are composed of protons, neutrons, and electrons. Because atoms are electrically neutral, the number of positively charged protons must be equal to the number of negatively charged electrons. Since neutrons do not affect the charge, the number of neutrons is not dependent on the number of protons and will vary even among atoms of the same element.
- https://phys.libretexts.org/Courses/Coalinga_College/Physical_Science_for_Educators_(CID%3A_PHYS_14)/08%3A_Energy_Physics_and_Chemistry/8.03%3A_Thermochemical_EquationsThe mass of C 2 H 6 is easily converted to the amount of C 2 H 6 from which the heat energy q is easily calculated by means of Eq. (2). It is important to realize that the value of ΔH m given in therm...The mass of C 2 H 6 is easily converted to the amount of C 2 H 6 from which the heat energy q is easily calculated by means of Eq. (2). It is important to realize that the value of ΔH m given in thermochemical equations like \ref{1} or \ref{3} depends on the physical state of both the reactants and the products. The only way the problem can he avoided is for ΔH m of the reverse reaction to be equal in magnitude but opposite in sign from ΔH m of the forward reaction.
- https://phys.libretexts.org/Courses/Coalinga_College/Physical_Science_for_Educators_(CID%3A_PHYS_14)/03%3A_Atomic_Theory_and_Periodic_Table/3.02%3A_Atoms_and_the_Periodic_Table/3.2.01%3A_Basic_Atomic_TheoryAll modern scientists accept the concept of the atom, but when the concept of the atom was first proposed about 2,500 years ago, ancient philosophers laughed at the idea. It has always been difficult ...All modern scientists accept the concept of the atom, but when the concept of the atom was first proposed about 2,500 years ago, ancient philosophers laughed at the idea. It has always been difficult to convince people of the existence of things that are too small to see. We will spend some time considering the evidence (observations) that convinced scientists of the existence of atoms.
