Atomic size

Definition:

• Atomic size, also known as atomic radius, refers to the size of an atom, specifically the distance from the nucleus to the outermost electron cloud.

Factors Influencing Atomic Size:

• Atomic size can be affected by the following factors:

Atomic Number:

• Generally, atomic size increases as you move down a group (vertical column) in the periodic table.
• Example: In Group 1 (e.g., sodium, potassium), atoms have larger atomic sizes as you move from top to bottom.

Number of Electron Shells:

• Atoms with more electron shells tend to be larger.
• Example: Sodium (Na) in the third period has three electron shells, making it larger than helium (He) in the first period with only one electron shell.

Effective Nuclear Charge:

• Atomic size decreases as you move across a period (horizontal row) from left to right in the periodic table.
• Example: In Period 3, sodium (Na) has a larger atomic size than chlorine (Cl) because of the increasing effective nuclear charge in the same period.

Examples of Trends:

• Noble gases, found in Group 18 (e.g., helium, neon), have the largest atomic sizes within their periods.
• Alkali metals in Group 1 (e.g., lithium, sodium) have larger atomic sizes than most other elements in their respective periods.

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Atomic size

Summary:

• Atomic size, or atomic radius, is the measure of the distance from an atom's nucleus to its outermost electron cloud. It is influenced by factors such as atomic number, number of electron shells, and effective nuclear charge. Generally, atomic size increases down a group and decreases across a period in the periodic table.