Difference Between Element Molecule and Compound

Main Difference – Element vs Molecule vs Compound

The terms element, molecule, and compound, have different definitions and properties as discussed below in this article. Although often we use the term compound to name any molecule, not all compounds are only molecules. There are many other chemical species that we can call a compound. An element is a substance that cannot be broken down further by chemical means. A molecule is a substance that is made out of two or more atoms bonded via chemical bonds. A compound is a molecule composed of different types of atoms bonded via chemical bonds. Therefore, a compound is also a type of molecule, but they are not the same. The main difference between element, molecule and compound is that an element is a substance that cannot be further divided into parts by chemical means whereas a molecule is a substance that can be further divided into parts by chemical means and a compound is also a type of molecule but is composed of different types of molecules.

Key Areas Covered

1. What is an Element
     – Definition, Periodic Table, Reactivity, Isotopes
2. What is a Molecule
     – Definition, Chemical Formula, Different Types
3. What is a Compound
     – Definition, Different Types
4. What is the Relationship Between Element Molecule and Compound
5. What is the Difference Between Element Molecule and Compound
      – Comparison of Key Differences

Key Terms: Atom, Atomic Number, Element, Chemical Bond, Compound, Covalent Bond, Electron Configuration, Ionic Bond, Mass Number, Molecule

What is an Element

A chemical element is a substance that cannot be broken down by chemical means. Many different chemical elements have been discovered so far. They have a unique property, i.e., the number of protons in the nucleus. This is called the atomic number. The atomic number of an element is a fixed value for a certain element. Two elements cannot have the same atomic number. Any change in the atomic number changes the element. However, elements can be changed through nuclear reactions.

Periodic Table

Chemical elements are arranged in the periodic table of elements based on their atomic number and the electron configuration. A chemical element can also be explained as a species of atoms or a group of atoms. This is because the atoms that can be found anywhere belong to a certain chemical element. This happens because of the uniqueness of the atomic number for a certain chemical element. 

Figure 1: Periodic Table of Elements

In the periodic table of elements, there are different categories of chemical elements. Some of the classifications are shown below.

• Metals, non-metals, and metalloids
• s block elements, p block elements, d block elements and f block elements.
• Alkali metals, alkaline earth metals, transition metals.
• Halogens, noble gases, etc.

Reactivity

Some chemical elements are inert; some are less reactive while some are very reactive. Inert chemical elements include the group of noble gasses. All other elements can undergo chemical reactions easily. This is because, they do not have incomplete electron shells according to the electron configuration of noble gases, and thus are very stable as individual atoms. They have no reason to react with other elements. But the other chemical elements have incomplete electron configurations. Therefore, they undergo different chemical reactions in order to fill their electron shells. The less reactive chemical elements have a partially filled, yet stable electron configurations.

Figure 2: Metal Activity Series

Isotopes

Some chemical elements are highly radioactive since they are highly unstable. They decay over time until they get a stable state. Some chemical elements have different forms known as isotopes. Isotopes of a certain chemical element have the same atomic number but a different mass number. This means, the number of protons in their nuclei is the same; hence, they belong to the same chemical element. But the number of neutrons in the nuclei are different from each other.

Figure 3: Isotopes of Hydrogen Chemical Element

There are names and symbols used to name each and every element. Most of these names are Latin words, and the symbols are derived accordingly.

What is a Molecule

A molecule is a group of two or more atoms chemically bonded to each other and is neutral. A molecule may contain the atoms of the same chemical element or different chemical elements. A molecule in chemistry is a polyatomic chemical species with a neutral electrical charge. Molecules can be categorized into different groups depending on the chemical and physical properties of molecules.

A molecule may contain atoms bonded via either covalent bonds or ionic bonds. A covalent bond is formed when two atoms share their unpaired electrons. An ionic bond is an electrostatic attraction between two or more atoms.

Chemical Formula

The composition of atoms in a molecule is given by its chemical formula. The empirical formula gives the ratio between the atoms. For example, C3H6 is the chemical formula of propene. There are three carbon atoms and six hydrogen atoms bonded to each other. The empirical formula for this molecule is CH2.

Figure 4: Some Common Molecules

Different Types of Molecules

• Based on the types of atoms present in a molecule, it can be either homonuclear or heteronuclear. Homonuclear molecules are composed of atoms of the same element. Heteronuclear molecules are composed of atoms of different chemical elements.
• Molecules can be either organic or inorganic. Organic molecules are composed of essentially C,H along with some other elements. Inorganic molecules may have different combinations of different chemical elements.
• Number of atoms per molecule: diatomic molecules, triatomic molecules, polyatomic molecules.
• Molecules composed only of covalent bonding are covalent molecule, and the molecules containing ionic bonding are ionic molecules.
• According to geometry, molecules can be either symmetrical or asymmetrical molecule. For example, the linear geometry of CO2 makes it a symmetrical molecule.

Likewise, there are many types of molecules that can be found in nature. They have different abundances. The individual atoms are not molecules. For example, Helium (He) is not a molecule.

What is a Compound

A compound is a chemical species that is formed when two or more atoms join together chemically, with covalent or ionic bonds. All compounds are molecules, but not all molecules are compounds. Homonuclear molecules are not compounds. Only heteronuclear molecules are considered as compounds. Compounds can be grouped in different ways, only a few are mentioned below.

Figure 5: This is a covalent compound that contains atoms of different chemical elements

Different Types of Compound

• Based on the number of atoms, compounds can be diatomic, triatomic or polyatomic.

• Based on the type of chemical bonding, covalent compounds contain covalent bonds, and ionic compounds contain ionic bonds.

• Based on the complexity, some compounds are simple compounds while other are complex compounds.

• Based on the components (cation, anions, ), compounds can be organic compound or inorganic compound. Organic compounds include hydrocarbons, carboxylic acids, amides, ammines, alcohols, etc. Inorganic compounds include oxides, hydrides, halides, nitrites, nitrates, carbonates, etc.

Relationship Between Element Molecule and Compound

• Molecules are made out of atoms of same or different chemical elements. Molecules containing different types of elements are called compounds.

Difference Between Element Molecule and Compound

Definition

Element: A chemical element is a substance that cannot be broken down by chemical means.

Molecule: A molecule is a group of two or more atoms chemically bonded to each other.

Compound: A compound is a chemical species that is formed when two or more atoms join together chemically, with covalent or ionic bonds.

Members

Element: There are  115 known chemical elements.

Molecule: Substances composed of two or more atoms chemically bonded to each other are molecules.

Compound: Substances composed of two or more atoms of different chemical elements are compounds.

Unique Properties

Element: Chemical elements contain a unique atomic number.

Molecule: Molecules can be either homonuclear or heteronuclear.

Compound: Heteronuclear molecules are compounds.

Chemical Element

Element: An element contains similar atoms.

Molecule: A molecule can have atoms of either the same element or different elements.

Compound: A compound has atoms of different elements.

Chemical Bonding

Element: Atoms of different elements can form different types of chemical bonds depending on their electron configurations and the stability.

Molecule: Molecules can have either covalent bonds or ionic bonds.

Compound: Compounds can have covalent bonds, ionic bonds or metallic bonds.

Examples

Element: Some examples for chemical elements include oxygen, hydrogen, nitrogen, copper, zinc, etc.

Molecule: Some examples for molecules include oxygen (O2), ozone (O3), water (H2O), etc.

Compound: Some examples for compounds include sodium chloride (NaCl), calcium carbonate (CaCO3), etc.

Conclusion

Molecules are composed of chemical elements. Molecules that contain two or more different chemical elements are known as compounds. The main difference between element molecule and compound is that an element is a substance that cannot be further divided into parts by chemical means whereas a molecule is a substance that can be further divided into parts by chemical means and a compound is also a type of molecule but is composed of different types of molecules.

References:

1. Helmenstine, Anne Marie. “What Is an Element? Definition and Examples.” ThoughtCo, Available here.
2. “Chemical element.” Wikipedia, Wikimedia Foundation, 6 Dec. 2017, Available here.
3. Helmenstine, Anne Marie. “What Is a Chemical Compound?” ThoughtCo, Available here.
4. Helmenstine,  Anne Marie. “Brush Up On Your Chemistry Terms!” ThoughtCo, Available here.

Image Courtesy:

1. “Simple Periodic Table Chart-e”By Offnfopt – Own work, Public Domain) via Commons Wikimedia
2. “Protium deuterium tritium” By Lamiot for french version, from Dirk Hünniger – self, translation from Dirk Hünniger (german wikipedia) (CC BY-SA 3.0) via Commons Wikimedia
3. “Metham (chemical compound)” By Gyimhu – Own work (Public Domain) via Commons Wikimedia
4. “Common molecules and atoms” By Original uploaded by: Adrignoladerivative work: Redrose64 – Own work based on: Common molecules and atoms.png (CC BY-SA 3.0) via Commons Wikimedia

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