The Beautiful Logic of Chemistry Quiz

Answer: It is an acid

The Bronsted-Lowry definition of an acid is anything that donates a proton. A proton is a hydrogen ion, as a hydrogen atom is (usually) one electron whizzing around one proton. In contrast to an acid, a base is anything which accepts a proton.

The trap some may have fallen into is putting "It is an ion" as an answer. True, upon losing a hydrogen ion, many compounds will become ionised themselves (after all, they are losing a positively charged entity and so are likely to be left negatively charged). However, this is not part of the definition of an acid and so cannot be known for certain from the predicate. This answer would only be true if the compound was uncharged to begin with.

Answer: It is an atom of carbon

Atoms of elements are usually described as being made up of three components - protons, neutrons, and electrons. If the number of neutrons changes, these are described as isotopes of the same element (examples of these are carbon-12, carbon-13 and carbon-14). If the number of electrons changes, these are described as being different ionisation states (for example, iron 2+ has one more electron that iron 3+). However, if the number of protons changes, the element changes. It is the proton number that defines which element is which.

The vast majority of carbon atoms are carbon-12 atoms (i.e. containing 6 protons and 6 neutrons), but it is still incorrect if you chose "It is an atom of carbon-12" as your answer. This answer is likely, but we cannot know this a priori from the statement given in the question. Further investigation (e.g. mass spectrometry) would need to be carried out in order to validate or falsify the statement "it is an atom of carbon-12".

Answer: It has a formal charge of -1

Atoms are the simplest particles which define what an element is. They contain charged sub-atomic particles called electrons (which are negative) and protons (which are positive). In atoms of gold, or zinc, or hydrogen, or carbon, the number of protons always equals the number of electrons, and so the overall charge is zero. Atoms may gain or lose electrons during a reaction, and in doing so make the number of protons and electrons unequal. If an atom gains electrons, it becomes a negatively charged ion, and if it loses electrons, if becomes a positively charged ion.

Answer: There is no formal charge on the atom

The noble gases are named as such because they stand alone - they rarely react with other elements and so usually exist as monatomic entities. This lack of reactivity is due to a full outer shell of electrons, which is characteristic of this group. However, a full outer shell of electrons is not a solid definition of a noble gas. For example, a chlorine atom can gain one electron and have a full outer shell of electrons, but this is not a noble gas. An atom of lithium can lose an electron to gain a full outer shell of electrons, but, again, this is not a noble gas. A noble gas can therefore be said to be an atom with a full outer shell of electrons AND which has no formal charge.

The answer "The atom is fairly nonreactive" is (as stated above) a typical quality of noble gases, but this would not lead us to deduce without doubt that the element in question was a noble gas, even if it did contain a full outer shell of electrons. Similarly, the statement "The atom has an even number of protons" is necessary, but not sufficient, for this element to be called a noble gas.

Answer: Atom X is covalently bonded to Atom Y

There are several types of bond/interactions in chemistry. These may be hydrogen bonds, which are intermolecular interactions between a relatively positive and a relatively negative component. There can also be ionic bonds, which involve interactions between formal positive and formal negative charges, and so are much stronger than hydrogen bonds. One of the most important bonds in biochemistry is the covalent bond, which is defined as the sharing of a pair of electrons between two atoms.

Answer: It is a radical

In an atom, electrons exist in shells, which can be subdivided into sub-shells, which can be further sub-divided into orbitals. These orbitals can contain a maximum of two electrons (as stated in Pauli's Exclusion Principle), which are described as electron pairs. Radicals (or free radicals) are defined as entities which have unpaired valence electrons.

Answer: It contains as least one carbon-carbon double bond

In organic chemistry, the terms "alkane" and "alkene" give us information about the types of bonds that are found in hydrocarbons. Alkanes contain only carbon-carbon single bonds. This means that each carbon atom is only bonded to each neighbouring carbon atom by a single pair of electrons. In contrast, alkenes contain at least one carbon-carbon double bond. In this bond the neighbouring carbon atoms share two pairs of electrons.

The alkene in question may well contain an odd number of carbons, but this can neither be proved nor disproved using the information provided.

Answer: This sample has a mass of 4 grams

Avogadro's number is a huge number that is used to define a mole. A mole is one of the seven so-called fundamental units, and is a measure of an amount of substance. Avogadro's number is 6.022 x 10^23. This means that 1 mole of substance contains 6.022 x 10^23 molecules of that substance. Avogadro's number can also be defined as the number of atoms in 12 grams of carbon-12.

The relative molecular mass of carbon-12 is 12. The relative molecular mass of water is 18. Therefore, 1 mole of water has a mass of 18 grams.

Helium has a relative molecular mass of 4 and so 1 mole of helium atoms have a mass of 4 grams.

Answer: Compound X is a solid

The state of matter (solid, liquid, or gas) is determined by the intermolecular interactions. The stronger these are, the less freedom the atoms/molecules have. Thermal energy provided by the surroundings agitates the atoms/molecules which may gain enough energy to overcome these interactions. Therefore, at room temperature, substances with strong intermolecular bonds are more likely to be solid, whilst those with weaker intermolecular bonds are more likely to be liquid or gaseous.

Answer: No

The uncertainty principle, as developed by Werner Heisenberg, refers to the inability to deduce the exact momentum and exact position of a particle in space. The more accurate a measurement you make for one of these values, the more ambiguous the second value becomes.

When considering concepts such as this, I often take solace in the words of Richard Feynman - "If you think you understand quantum mechanics, you don't understand quantum mechanics".