History of the Atom
Who used the cathode ray tube to discover the electron?
J.J. Thomson
How many protons are in a sodium atom?
11
What do isotopes of the same element differ in?
Number of neutrons (and mass number)
An atom with 11 protons and 10 electrons has what charge?
1+
True or False: The number of protons equals the atomic number.
True
Which scientist’s gold foil experiment showed that atoms have a small, dense, positively charged nucleus?
Ernest Rutherford
An atom of magnesium (Mg, atomic #12) has 12 protons and 12 neutrons. What is its mass number?
24
Carbon exists as C-12 (98.9%) and C-13 (1.1%). What is its average atomic mass?
12.01 amu
Oxygen becomes O²⁻ by gaining or losing how many electrons?
Gains 2 electrons
What part of the atom makes up most of the space?
Electron cloud
What major conclusion did Rutherford’s gold foil experiment lead to about the structure of the atom?
The atom is mostly empty space
Which two subatomic particles are found in the nucleus?
Protons and neutrons
Neon has two isotopes: Ne-20 and Ne-22. If the average atomic mass is 20.2, which isotope is more abundant
Ne-20
Write the number of protons, neutrons, and electrons for Cl⁻ (chlorine-35).
17 protons, 18 neutrons, 18 electrons
What is the total number of protons and neutrons in an atom of phosphorus-31?
31
Which model of the atom was called the “plum pudding model”?
Thomson’s model
How many neutrons are in an atom of calcium-42 (Ca, atomic #20)?
22
Strontium has isotopes Sr-86 (10%), Sr-87 (20%), Sr-88 (70%). Calculate its average atomic mass.
87.6 amu
What is the difference between a cation and an anion?
A cation is positively charged (loses electrons), an anion is negatively charged (gains electrons).
A sulfur atom (S, atomic #16) has a mass number of 34. How many neutrons does it have?
18
Which two scientists built the first correct model of DNA, a polymer of nucleotides?
James Watson & Francis Crick
If an atom has 16 protons, 16 electrons, and 18 neutrons, what is the element and its mass number?
Sulfur-34
Bromine has two isotopes: Br-79 and Br-81. If the average atomic mass is 79.9, which isotope is more abundant?
Br-79
An atom of aluminum (Al, atomic #13) forms Al³⁺. How many electrons does it have and what type of ion is it?
10 electrons and cation
If the average atomic mass of copper is 63.5, which isotope is more abundant: Cu-63 or Cu-65?
Cu-63