Raio Atômico - Brasil Escola

Summary

In this chemistry class, Professor Choven explains atomic radius, a key periodic property of elements. The atomic radius refers to the distance from an atom's nucleus to its outermost electron. Two factors influence atomic radius: the number of electron shells (periods) and the effective nuclear charge. As periods increase, so do the number of shells, which increases the atomic radius. Effective nuclear charge increases from left to right, shrinking the atomic radius. The professor also covers ionic radii, explaining that cations (ions that lost electrons) have smaller radii, while anions (ions that gained electrons) have larger radii. The session concludes with a summary of these concepts and their behavior in the periodic table.

Takeaways

• 😀 Atomic radius refers to the size of an atom, specifically the distance from the nucleus to the outermost electron.
• 😀 The atomic radius is measured using an X-ray technique, which calculates the distance between two nuclei and divides it by two to determine the atom's radius.
• 😀 The atomic radius is influenced by two main factors: the number of electron layers (periods) and the effective nuclear charge.
• 😀 As the number of electron layers increases (moving down a period in the periodic table), the atomic radius also increases.
• 😀 Effective nuclear charge refers to the force exerted by the nucleus on its outermost electron, which affects the size of the atom.
• 😀 A higher effective nuclear charge results in a stronger attraction between the nucleus and electrons, leading to a smaller atomic radius.
• 😀 Conversely, a lower effective nuclear charge leads to a larger atomic radius, as the attraction between the nucleus and electrons is weaker.
• 😀 The atomic radius grows top to bottom in periods (more layers = larger radius) and right to left in groups (lower effective nuclear charge = larger radius).
• 😀 The largest atomic radius is found in francium, the last element in Group 1 of the periodic table.
• 😀 The size of ions differs from neutral atoms: cations (positive ions) have smaller radii than their neutral counterparts, while anions (negative ions) have larger radii due to the gain of electrons.

Q & A

What is atomic radius?

Atomic radius refers to the measurement of the size of an atom, specifically the distance from the nucleus to the outermost electron in the electron cloud (electrosphere).

How is atomic radius measured?

Atomic radius is measured using X-ray techniques that calculate the distance between two nuclei of atoms that are bonded. The value is then halved to find the atomic radius of a single atom.

What are the two main factors that influence atomic radius?

The two main factors that influence atomic radius are the number of electron shells (electrosphere) and the effective nuclear charge.

How does the number of electron shells affect atomic radius?

As the number of electron shells increases, the atomic radius becomes larger. This happens because the outermost electrons are farther from the nucleus, resulting in a larger atomic size.

What is effective nuclear charge, and how does it affect atomic radius?

Effective nuclear charge is the force exerted by the nucleus on the outermost electron. A higher number of protons in the nucleus leads to a stronger attraction, causing the atomic radius to decrease. Conversely, a lower effective nuclear charge results in a larger atomic radius.

How does the atomic radius change as you move across periods and groups in the periodic table?

Across periods (left to right), atomic radius decreases because the effective nuclear charge increases, drawing electrons closer to the nucleus. Down a group (top to bottom), atomic radius increases due to the addition of more electron shells, which increases the distance between the nucleus and outer electrons.

Which element has the largest atomic radius in the periodic table?

Francium, located in Group 1 (Period 7), has the largest atomic radius in the periodic table.

What happens to the atomic radius when an atom becomes a cation?

When an atom becomes a cation by losing electrons, its electrosphere shrinks, leading to a smaller atomic radius.

How does the atomic radius of a cation compare to its neutral atom?

A cation has a smaller atomic radius compared to its neutral atom because it loses electrons, reducing its electrosphere.

What is the difference between a neutral atom and an anion in terms of atomic radius?

An anion has a larger atomic radius than its neutral atom because it gains electrons, which increases the size of its electrosphere.