1. The following particles all have the same
electronic arrangement of 2, 8, 8:
K+, Ca2+, Cl-, Ar, S2-.
a. Which particle has the same number of
protons as electrons?
b. Which particle has 20 protons but only 18
electrons?
c. Which particle has one more electron than
protons?
d. Which particle is an atom?
2. An atom of phosphorus has an atomic number
of 15 and a mass number of 31. Give the
number of protons, neutrons and electrons in
an atom of phosphorus.
3. Silicon’s three most stable isotopes are 28Si, 29Si and 30Si.
a. Define the term “isotope”
b. Silicon has a relative atomic mass of 28.1.
Choose the most abundant isotope from
the list of silicon’s three most stable
isotopes. Explain your answer.
4. 32S and 34S are the two most common isotopes
of Sulphur. Describe the similarities and
differences between these two isotopes.
5. Element X has an atomic number of 17.
a. Which group of the periodic table will this
element belong to?
b. Give the atomic number of the element
that would be directly above element X in
the periodic table.
6. An element reacts by losing its outer shell
electrons to form cations. Is this element a
metal or a non-metal?
7. What do the noble gas group all have in
common?
8. Stearic acid is used for making soap. The
melting point and the boiling points of stearic
acid are 70°C and 287°C respectively. Sketch a
graph to show the changes in temperature
when molten stearic acid is cooled to room
temperature.
9. Classify the following changes of state into two
groups: Heat taken in and heat given out by the
particles:
sublimation,
condensation,
evaporation, boiling, melting and freezing.
10. Why does the scent of perfume spread?
and why does the scent wear off faster in warm
weather than in cold?