We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.
Chemistry

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

What Is the Crisscross Method?

By Paul Reed
Updated: May 21, 2024
Views: 15,095
Share

The crisscross method is a way to determine the chemical formula of compounds by using the valence of the atoms. Atoms have a central core of protons and neutrons, with layers of electrons circling the core in layers called shells. The outermost shell may contain too many or few electrons, which is described by a plus or minus valence number. Compounds form by exchanging these electrons in reactions called ionic bonding, where the electrons are shared between two or more atoms.

When an atom with two extra electrons combines with another containing one less electron, it takes two of the second atom to form the compound. Silicon contains two extra electrons in its outer shell, while oxygen contains one electron short of a full shell. The ionic formula for the two atoms would be Si+2 and O−1, which shows the ionic valence for each.

Using the crisscross method, the resulting compound can be written by transferring the valence of each atom to the other, and writing them as a subscript. The molecule resulting from the combination of silicon and oxygen is silicon dioxide, or SiO2. The +2 valence of the silicon atom is crossed to the oxygen, and the −1 is transferred or crossed to the silicon. Crossing the valences between the two atoms when describing the molecule led to the term crisscross method.

The reaction of the two atoms eliminates any electron charge, because the atoms combine in the ratios needed to use all excess electrons. With a balanced number of electrons the valence is considered zero, and there is no plus or minus sign used in a molecular formula. Ionic molecules tend to be very stable, because the electrons are shared between the atoms, making a very strong chemical bond.

A process called reduction is used to create the proper molecular name when the ionic valences are multiples of smaller numbers. Barium and oxygen can combine to form barium oxide, with each of the atoms containing a valence of two. Using the crisscross method, the valence of 2 would be crossed to the atomic name of the other atom, resulting in a molecule named Ba2O2. The subscripts can be divided by 2, so the correct molecule is BaO, and the valences have been reduced to the minimum needed.

The crisscross method will also work when the molecules are made from more complex groups, such as zinc acetate. Zinc (Zn) with a +2 valence, can chemically combine with an acetate molecule (C2H3O2) with a −1 valence. The method switches the two valences to show that one zinc atom will combine with two acetate molecules to form Zn(C2H3O2)2. As long as the molecule has a known valence, the crisscross method can be used to determine the correct molecular structure of any compound.

Share
All The Science is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
Share
https://www.allthescience.org/what-is-the-crisscross-method.htm
Copy this link
All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.

All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.