First Year Chemistry

Determining the Composition of an Atom

Chemistry Guided Instructional Activity 2-1
Unit: Structure of Matter Reading: Chapter 3

Working Mode: Pairs. Solve the problems on this sheet of paper. Each student must submit their own work.
Learning Objective: Determine the number of protons, neutrons, electrons, atomic number, mass number, isotope and charge of an atom.
Key Words: protons, neutrons, electrons, atomic number, mass number, nuclear symbol and ionic charge.

Question 1: An isotope of Chlorine has a mass number of 37 and no charge.

Student 1: Determine the atomic number of the atom.

Student 2: Determine the number of protons of the atom.

Student 1: Determine the number of electrons in the atom.

Student 2: Determine the number of neutrons in the atom.

Student 1: Write the nuclear symbol of the atom.

Question 2: Oxygen has three naturally occurring isotopes, Oxygen – 16, Oxygen – 17, and Oxygen – 18.

Student 2: Determine the atomic number of oxygen.
Student 1: Give the number of neutrons in each oxygen isotope.

Student 2: State in what way these atoms of oxygen are the same and in what ways they are different.

Question 3: Given the following nuclear symbol determine the following information.

Student 1: The mass number.

Student 2: The atomic number.

Student 1: The number of protons.

Student 2: The number of neutrons.

Student 1: The number of electrons.

Student 2: The name of the element.

Question 4: Fill in the following table.

symbol protons neutrons electrons

(a) 18 20 18

(b) ²⁷Al³⁺