Study Guide: Chemistry -- Atomic Structure
History of the Atom o Democritus – existence of atoms o John Dalton – Dalton’s Atomic Theory
1. All matter is made of atoms.
Atoms are indivisible and indestructible.
2. Atoms of the same element are identical in mass and properties .
3. Atoms of different elements combine in whole number ratios to form compounds.
4. Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.
Note: The parts that are still held as true are bolded and underlined. The other parts (plain text) are not true. o J.J. Thomson
• discovery of the electron
• cathode ray tube
• plum pudding model of the atom o Ernest Rutherford o Niels Bohr
• discovery of the nucleus
• the atom is mostly empty space
• gold foil experiment
• Rutherford model of the atom
• further developed the nuclear model of the atom
• planetary model
• energy levels
• model did not work for all elements
Subatomic particles o proton, neutron, electron
• charge, relative mass, location in the atom
Structure of Different Atoms o Atomic Number o Mass Number o Isotopes o Ions o Complete chemical symbols o How to determine the number of protons, neutrons and electrons in an atom. o Atomic Mass (weighted average)
Vocabulary alpha particle atom atomic mass atomic mass unit (amu) atomic number cathode ray
Dalton’s atomic theory electron isotope mass number neutron nucleus proton

Match each definition with the appropriate term. (1 pt each)
_____ 1. atoms with the same number of protons but different numbers of neutrons
_____ 2. the smallest particle of an element that retains the properties of that element
_____ 3. the weighted average of an element’s isotopes
_____ 4. the center-most part of an atom where the protons and neutrons are located
_____ 5. equal to 1/12 the mass of a carbon-12 atom (approximately the mass of one proton or neutron)
Select the best choice and write the letter in the blank before the question. a. atom b. atomic mass c. atomic mass unit d. isotopes e. nucleus f. radiation
6. Atoms of each element contain a unique number of _______ in their nuclei.
7. Two isotopes of the same element may have different
8. An atom has no net electrical charge because
9. The atomic number of an element is
10. Mass number is
11. Isotopes are atoms of the same element that have different

12. Fill in the blanks of the table. (6 points)
Name Symbol Charge Relative Mass proton 1 amu neutron n 0 electron
1-
13. Use a periodic table to complete the following chart. (18 points)
Element Atomic
Number
Mass
Number
Number of protons
Number of electrons
Number of neutrons
Complete
Chemical
Symbol
9 9
12 6
84
84 126 selenium 79
6
14 6
15. Calculate the atomic mass of gallium (Ga). Gallium has two isotopes: 69
69
Ga and 71 Ga.
Ga has a relative abundance of 60.12% and an atomic mass of 68.9257 amu. 71 Ga has a relative abundance of 39.88% and an atomic mass of 70.9249 amu. Show all your work.
(4 points)

Describe Rutherford’s gold foil experiment. Include a diagram.
Draw a picture of both the plum pudding and nuclear atom. Label each drawing . You must identify which diagram is the plum pudding model and which one is the nuclear atom!!!