Introductory principles
Francine Taylor-Campbell, Contributor

Clement Radcliffe, principal of Clarendon-based Glenmuir High School, conducts a CXC seminar at the Girls' Guide Association of Jamaica headquarters on Waterloo Road, St. Andrew, earlier this year. - Junior Dowie/Staff Photographer

Welcome to another AIDS TO CHEMISTRY lesson series. We hope to use the syllabus to guide us as to the areas we should focus on and by answering questions at the end of each lesson. We will assess how well we have understood the concepts presented. Special notes or comments will be used to highlight important points or common mistakes students can make.

SYLLABUS REQUIREMENTS

Students should be able to: explain the differences between the three states of matter in terms of energy and arrangement of particles; describe the structure of atoms of atomic number one to 20; state properties of electrons, protons and neutrons; define atomic number, mass number and relative atomic mass; define isotopy and list three uses of isotopes.

Answer the following multiple choice questions.

1. Which statement about the behaviour of the particles in a gas is not correct?

A. They spread throughout the vessel in which they are contained.
B. They are able to move at high speeds.
C. They are arranged in regular patterns.
D. There are large spaces between the particles.
E. Their collisions with the walls of the vessel cause pressure.

2. An atom of element X has the symbol 7 3X. Which statement about X is correct?

A. It is in Group III of the Periodic Table
B. It is in Group VII of the Periodic Table
C. In one atom, the number of protons + the number of electrons is 6.
D. In one atom, the number of protons + the number of neutrons is 10.
E. The electron arrangement is 2:5.

3. Two particles, X and Y, have the following atomic particles:

X - 6 protons and 6 neutrons
Y - 6 protons and 8 neutrons

Which term describes X and Y?

A. allotropes
B. ions
C. isomers
D. isotopes

4. An inflated balloon will shrink if placed into a refrigerator. This is because the lower temperature causes the gas particles in the balloon to move

A. faster and become closer together.
B. faster and become further apart.
C. slower and become closer together
D. slower and become further apart

5. The atoms 31 15 P and 32 16 S have the same

A. nucleon number.
B. number of electrons.
C. number of neutrons.
D. number of protons.

ANSWERS AND COMMENTS

1C. Gases are not arranged in regular patterns; instead they fill the space of any container in which they are placed and have no shape.

2C. In element X the number of protons (atomic number) is the bottom number which is 3 and this is also equal to the number of electrons in an uncharged atom. Therefore the protons + electrons = 3 + 3 = 6. Element X is not in Group 3 or 7 of the Periodic Table as its electronic configuration 2 : 1 (3 electrons) puts it in Group I (1 electron in the outer shell).

3D. X and Y have the same number of protons (atomic number) but different number of neutrons, hence they are isotopes.

4C. An inflated balloon contains gas particles which have spread out. Upon freezing the energy of the particles and hence their movement is reduced causing them to slow down and come closer together. Eventually they will freeze and become a solid having close arrangement of particles.

5C. The number of neutrons is found by subtracting the number of protons from the mass number. N = M - P. If this is done for P then 31 - 15 = 16 and for S 32 - 16 = 16. The atoms P and S contain the same number of neutrons = 16.