The “negative oxygen ion face mask” that is selling in vending machines across Singapore.

The COVID-19 world is a strange place. The negatives are positive. We pray for negative results when we go for a swab test. The US President, Donald Trump, joked that he was tested “positively toward negative.” And now, we even have a “negative oxygen ion face mask” that does the positive thing of providing “cleaner air qualities”.

Its key feature is the “negative oxygen ion cotton” layer. The packaging explains how it works in a woolly, unclear manner. We can only guess that the cotton layer produces negative oxygen ion when air passes through it.

What Exactly Is a “Negative Oxygen Ion”?

There are many types of oxygen-containing ions that are negatively charged. In minerals like sodium oxide and calcium oxide, oxygen exists as the monoatomic oxide anion, O2-.

There are also polyatomic anions. One example is the superoxide anion, O2. It contains a single covalent bond between its two oxygen atoms. Only one of the two atoms has a stable octet electron arrangement. The other atom has 7 electrons only.

Another polyatomic anion oxygen can form is the peroxide anion, O22-. Like superoxide, peroxide contains a single covalent bond between its two oxygen atoms. However, both atoms have a stable octet electron arrangement.

Yet, oxygen mainly exists as diatomic molecules in the lower atmosphere. Compared to superoxide and peroxide, oxygen molecules are more stable. Only when energy is supplied, would the stable oxygen molecules gain extra electrons to form superoxide and peroxide.

Can Cotton Produce “Negative Oxygen Ion”?

For the face mask to produce “negative oxygen ion”, its cotton layer must lose its electrons to the oxygen molecules that pass through it. Physicists call the loss and gain of electrons upon contact triboelectrification.

While we do not thank them for this cheem word, they have left us with a useful triboelectric series to find out how well a material loses electron. Cotton is quite low in the series, with a small tendency to lose electrons when the air is sufficiently humid.

Furthermore, oxygen molecules only gain an extra electron when sufficient energy is supplied. Currently, there is no strong scientific evidence that the cotton layer can produce sufficient “negative oxygen ion” to have any effect on virus particles.

Is It All Fake News Then?

Indeed, we do not yet have robust proof about the added benefit of the “negative oxygen cotton layer”. But there is a study that suggests that negative ions in the air prevents the airborne transmission of influenza virus.

In the study, scientists used an electric ioniser that expends electricity to form negative ions. These negative ions then transfer their extra electrons to particles in the air, making them negatively charged. This causes them to become attracted to a positively charged collector plate.

The question is, can a mask do the same without any energy input? Or is there a lie to be unmasked?

Data-Based Questions à la Paper 2 Section B

QUESTION 1: Atomic Structure

Superoxide and peroxide are polyatomic anions. Explain what it means by polyatomic anions.

Polyatomic anions are made up of multiple atoms that are covalently bonded, with an overall negative charge.


When sufficient energy is supplied, oxygen molecule can gain an electron to become the superoxide anion, O2.

Write a half-equation for the formation of superoxide. Using the half-equation, suggest if this process is oxidation or reduction. [2 marks]

O2 + e ⟶ O2

The gain of electron is a reduction process. Therefore, oxygen is reduced to form superoxide.


Find the oxidation state of oxygen in superoxide. Suggest why it is not a whole number. [2 marks]

The sum of the oxidation state is equal to the overall charge of superoxide. Let x be the oxidation state of oxygen in superoxide.

2x = -1
x = -0.5

Therefore, the oxidation state of oxygen in superoxide is -0.5. It is not a whole number as it is the average oxidation state of the two oxygen atoms in a peroxide anion.

QUESTION 4: Chemical Bonding

The name superoxide suggests that the polyatomic anion of oxygen has exceptionally high reactivity.

By comparing the arrangement of electrons in the superoxide anion to oxygen molecules, explain why the superoxide anion is highly reactive. [2 marks]

In oxygen molecules, both oxygen atoms have the stable electronic configuration of the noble gas neon.

However, in the superoxide anion, one of the oxygen atoms has 7 electrons. Therefore, to obtain the noble gas electronic configuration, the superoxide anion can readily gain or share electrons by reacting with another substance.