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Understand the subatomic composition of the atom and the concepts of atomic number, mass number, and isotopes.
Summarize cathode rays, the discovery of the electron, proton, and neutron.
For a long time, Dalton's atomic theory suggested that atoms were the ultimate, indivisible particles of matter. However, late 19th and early 20th-century experiments proved atoms are actually made of smaller sub-atomic particles.
Needs diagrams of cathode ray tubes and Rutherford's gold foil experiment to visualize the historical evidence.
A split educational scientific diagram. On the left, a cathode ray tube showing a glowing beam of electrons traveling fr…
Define Z, A, isotopes, and isobars.
When Rutherford bombarded a thin gold foil with -particles, most passed right through, but a few bounced back. He concluded that an atom is mostly empty space, with a tiny, dense, positively charged center called the nucleus.
Calculate protons, neutrons, and electrons for Bromine-80.
Problem. Calculate the number of protons, neutrons, and electrons in .
Determine the atomic symbol from particle counts.
We are given a chemical species with 16 protons, 18 electrons, and 16 neutrons. First, we determine the atomic number, which is always equal to the number of protons, giving us an atomic number of 16. The element with atomic number 16 is . Next, we calculate the atomic mass number by adding the number of protons and neutrons together. This calculation gives a mass number of . Since the species is not neutral, we determine the charge by evaluating the excess electrons (), giving an anion with a charge. Combining this information into standard isotopic notation, the final symbol for the species is .
Identify the number of neutrons in a given isotope.
How many neutrons are in the nucleus of ?