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Elements are the simplest substances that cannot be broken down using chemical reactions. Each element is made of only one type of atom. For instance, hydrogen (H), carbon (C), and oxygen (O) are examples of elements. Elements are the building blocks for all other substances. They can join with other elements to form more complex compounds. It's like having a single type of Lego block; each block is an element.

Key points about elements:

• Pure substance.
• Consisting of only one type of atom.
• Cannot be chemically separated into simpler substances.

For example, the element oxygen (O₂) is essential for respiration in most living organisms.

Compounds are substances formed when two or more different elements are chemically bonded together. Unlike elements, compounds can be chemically decomposed into simpler substances. An example of a compound is carbon monoxide (CO).
In carbon monoxide, one carbon atom is bonded to one oxygen atom, forming a compound. Think of compounds as a combination of different Lego blocks that are snapped together to form a new structure.

Key points about compounds:

• Contain two or more different elements.
• Chemically bonded.
• Can be broken down into simpler substances by chemical reactions.

Another example is water (H₂O), which is made from hydrogen and oxygen atoms chemically bonded together.

Chemical bonding is the process by which atoms combine to form compounds. Atoms bond by sharing or transferring electrons. This bonding results in the elements coming together in specific ratios to form compounds. There are two main types of chemical bonds: covalent and ionic.

Covalent bonds occur when atoms share electrons. This type of bond is common in organic compounds like methane (CH₄) and is also found in carbon monoxide (CO). Ionic bonds occur when one atom transfers electrons to another atom, which creates ions that are attracted to each other. An example of an ionic bond is found in table salt (NaCl).

• Covalent Bond: Atoms share electrons.
• Ionic Bond: Atoms transfer electrons, creating charged ions.

Understanding chemical bonding helps explain how compounds form and why they have specific properties. For example, carbon monoxide (CO) forms through covalent bonding between carbon and oxygen atoms.