Question

What happens to atoms during a chemical reaction?

Short answer

Atoms are rearranged during a chemical reaction; they form new bonds without loss or gain of mass.

Step-by-step solution

Understanding Chemical Reactions

In a chemical reaction, atoms are rearranged to form new substances. They do not disappear or are created out of nowhere but instead are redistributed as bonds are broken and new bonds are formed.

Conservation of Mass

According to the law of conservation of mass, during a chemical reaction, the total mass of the reactants equals the total mass of the products. This implies that the same number of each type of atom is present before and after the reaction, ensuring that atoms are neither lost nor gained during the process.

Breaking and Forming Bonds

Atoms in the reactants are connected by chemical bonds. During a chemical reaction, these bonds are broken, and atoms are free to rearrange themselves. As they rearrange, they form new chemical bonds, resulting in the creation of different molecules as products.

Example Analysis

Consider the reaction of hydrogen gas \((H_2)\) with oxygen gas \((O_2)\) to form water \((H_2O)\). Here, the bonds between the hydrogen atoms and oxygen atoms are broken, then rearranged to form bonds in the water molecules. The number of each type of atom stays the same (2 H and 2 O), but they are now in a different arrangement.

Key concepts

Atoms

Atoms are the fundamental building blocks of matter in the universe. They are too small to see without specialized equipment but make up everything around us. Each atom consists of a nucleus containing protons and neutrons, surrounded by electrons that orbit the nucleus. The number of protons in the nucleus defines an element, such as hydrogen or oxygen. Atoms are incredibly stable and are not converted to other atoms in normal chemical reactions. Instead, they simply rearrange during chemical processes to form different substances. This stability is crucial to how chemical reactions work, ensuring that atoms are unchanged after reactions even though they form new products.

Conservation of Mass

Conservation of mass is an essential principle in chemistry that asserts mass is neither created nor destroyed in a closed system. During a chemical reaction, the mass of the substances at the beginning (reactants) is equal to the mass of the substances formed at the end (products). This is because atoms themselves retain their identity, merely changing partners or configurations. For instance, when hydrogen and oxygen gases react to form water, the total mass of hydrogen and oxygen remains constant before and after the reaction.
This principle helps chemists predict the outcomes of reactions and balance chemical equations by ensuring the number and type of atoms are conserved, even if their arrangements change.

Chemical Bonds

Chemical bonds are the forces holding atoms together in molecules. These bonds form due to the attraction between electrons of one atom and the nucleus of another. There are three main types of chemical bonds: ionic, covalent, and metallic.
- **Ionic Bonds** form when electrons are transferred from one atom to another, typically between metals and nonmetals. - **Covalent Bonds** occur when atoms, usually nonmetals, share electron pairs. - **Metallic Bonds** are found in metals, where electrons flow freely between atoms. In a chemical reaction, these bonds are broken and reformed. This rearrangement allows atoms to form new combinations, leading to the synthesis of different compounds that make the universe around us diverse.

Molecules

Molecules are the results of atoms joining together through chemical bonds. They are distinct units and can consist of two or more atoms. For example, an oxygen molecule is composed of two oxygen atoms bonded together (\(O_2\)), while a water molecule consists of two hydrogen atoms and one oxygen atom (\(H_2O\)).
Molecules can vary greatly in size and complexity, ranging from simple diatomic molecules like hydrogen gas \((H_2)\) to large biomolecules like proteins and DNA. The arrangement and type of atoms within a molecule determine its properties and behavior in reactions. Understanding molecules and the way they form is crucial in fields such as chemistry, biology, and materials science, as they provide the basis for comprehending the structures and reactions of all substances.