ChemMatters Puzzle: Chem by the Numbers
Chemists love numbers! Whether constants, such as the speed of light and standard pressure, or simply a
sample size, we use them all the time. In this puzzle, you are challenged to match the numbers 0 to 11 to a
given clue. These numbers are there, but in a scrambled arrangement. Below, we provide 12 clues. Match a
number to each. A number will be used once, so you can cross it off this set, if you wish.
0
1
2
3
4
5
6
7
8
9
10
11
Have fun!
____The size of the positive charge on the stannic ion.
____Exactly one-hundred millionth of the speed of light, in MKS (Meter, Kilogram, Second) units.
____The equivalent of 279 Kelvin on the degree Celsius scale.
____A filled f subshell contains this number of orbitals for electrons.
____In the IUPAC naming system, the base name unodec denotes this number of carbon atoms.
____The second significant figure in Avogadro's number.
____The number of neutrons in a Mg-22 ion of charge +2
____ The approximate vapor density at standard temperature and pressure (STP) of carbon monoxide gas.
(The vapor density is the density of a gas compared to that of air.)
____ The number of faces plus corners of a tetrahedron, a common molecular shape.
____ Given this equation: C3H8 + x O2  y CO2 + z H2O, what is the value of x?
_____The atomic number of the element in Period 2 with the biggest electronegativity value.
____ The mass, in grams, of 0.01 mole of calcium bromide.
Answers to the ChemMatters Puzzle
4 The size of the positive charge on the stannic ion.
3 Exactly one-hundred millionth the speed of light in a vacuum, in MKS units.
6 The equivalent of 279 degrees Kelvin is 6 on the degree Celsius scale (279 – 273)
7 A filled f subshell contains this number of orbitals for electrons.
11 In the IUPAC naming system, the prefix unodec denotes this number of carbon atoms.
0 The second significant digit in Avogadro's Number, 6.02 x 10
23
10 The number of neutrons in a Mg-22 ion of charge +2 = (22–12).
1 The approximate vapor density at STP of carbon monoxide gas (both air and carbon monoxide gas have
an average molar mass of about 28.8 g/mol).
8 The number of faces plus corners of a tetrahedron, a common molecular shape.
5 In C3H8 + x O2  y CO2 + z H2O: the value of x is 5 (to have 10 oxygen atoms).
9 The atomic number of the element in period 2 with the biggest electronegativity value.
2 The mass in grams of 0.01 moles of calcium bromide.
Notes by the author:
4 Stannum is the Latin name of tin; suffix ic implies the more positive charge of +2 and +4.
3 Speed is 3.00 x108 m/sec; 108 = one hundred-million; inverse is 10-8 , so net is 3x 100 = 3.
6 279K is 6 degrees above the freezing point of water on both scales. 1 oC = 1 K in size).
7 7 orbitals, each with a pair of electrons when filled.
11 An example: unodecanol-1 is C11H23OH.
0 In the coefficient 6.02, the 0 is a significant figure, not merely holding a place.
10 The number of neutrons in the Mg ion of mass number 22, atomic number 12.
1 Both are 1.29 g/L, with just about same molar mass of 28.8 g/mol.
8 In a perfect tetrahedron there are 4 faces( equilateral triangles) and 4 corners equidistant from center.
Lots of symmetry there!
5 Need 10 oxygen atoms on each side of the equation.
9 Of these eight elements, fluorine (Z= 9) exerts the strongest pull on a shared pair of electrons.
2 The formula is CaBr2, with molar mass of 200 g/mol.