Question

Which one of the following indicates the correct order of atomic size? (1) \(\mathrm{Be}>\mathrm{F}>\mathrm{C}>\mathrm{Ne}\) (2) \(\mathrm{Be}\mathrm{C}>\mathrm{F}<\mathrm{Ne}\) (4) \(F

Short answer

Option 3: Be > C > F < Ne

Step-by-step solution

- Understand Atomic Size

Atomic size refers to the distance from the nucleus to the outermost electrons of an atom. Generally, atomic size decreases from left to right across a period due to increasing nuclear charge, which pulls electrons closer to the nucleus.

- Assess Elements' Positions in the Periodic Table

Locate the elements mentioned in the options: - Beryllium (Be) is in Group 2, Period 2.- Fluorine (F) is in Group 17, Period 2.- Carbon (C) is in Group 14, Period 2.- Neon (Ne) is in Group 18, Period 2.

- Determine the Trend in Period 2

In Period 2, as we move from left (Be) to right (Ne), atomic size decreases. Therefore, the correct decreasing order of atomic size within these elements should start with Be (largest) and end with Ne (smallest).

- Compare with Given Options

Compare this trend with the options provided:1) Be > F > C > Ne2) Be < C < F < Ne3) Be > C > F < Ne4) F < Ne < Be < CThe correct order Be > C > F > Ne matches with option 3.

Key concepts

Atomic Size Trend

The concept of atomic size, also known as atomic radius, is essential for understanding how different elements compare to each other. Atomic size refers to the distance between the nucleus of an atom and its outermost electron. This size can vary due to several factors, chief among them being the element's position on the periodic table.
As we move from left to right across a period, the atomic size decreases. This occurs because each additional proton in the nucleus exerts a stronger positive charge. This 'nuclear charge' pulls the electrons closer, making the atom smaller. Thus, in a single period, elements on the left side (like Beryllium) will have a larger atomic size compared to elements on the right side (like Neon).
Understanding this trend helps predict how atoms behave in chemical reactions and bonds.

Periodic Table

The periodic table is an organized way to display all known elements. It arranges elements by increasing atomic number and groups them based on similar chemical properties. The table is crucial for predicting atomic size and understanding atomic trends.
Here's a closer look at where our specific elements lie:

• Beryllium (Be) is in Group 2, Period 2.
• Carbon (C) is in Group 14, Period 2.
• Fluorine (F) is in Group 17, Period 2.
• Neon (Ne) is in Group 18, Period 2.

It's clear from these positions that all these elements fall within the same period (Period 2), meaning they have the same number of electron shells. However, their atomic size varies based on their nuclear charge, which increases as we move across the period from left to right.

Nuclear Charge

Nuclear charge is the total charge of all the protons in the nucleus of an atom. This charge directly impacts the atomic size. In essence, a higher nuclear charge means a stronger pull on the electrons, reducing the atomic radius.
In Period 2 of the periodic table: Beryllium (with 4 protons) has a smaller nuclear charge compared to Neon (with 10 protons). This difference in nuclear charge affects the atomic size significantly, resulting in Be having a larger atomic size than Ne.
When comparing elements within the same period, like Be, C, F, and Ne, the atomic size order can be deduced by understanding their increasing nuclear charge. Therefore, the atomic size decreases as you move from Be to Ne: Be > C > F > Ne.