PROPRIEDADES DA TABELA PERIÓDICA | Resumo de Química Enem. Professor Felipe Sobis

Summary

In this lecture on periodic properties, the instructor explains key concepts such as atomic radius, electronegativity, ionization energy, and electron affinity, and how these properties follow specific trends across the periodic table. Atomic radius increases from top to bottom and decreases from left to right. Electropositivity and ionization energy follow similar patterns, while electronegativity increases as you move right and up in the table. The instructor also discusses exceptions, like noble gases, and emphasizes the importance of understanding these trends for exams like ENEM to predict how elements behave in chemical reactions.

Takeaways

• 😀 Atomic radius increases as you move down a group (top to bottom) and decreases from left to right across a period.
• 😀 Electronegativity increases from left to right across a period and decreases as you move down a group.
• 😀 Electropositivity increases from left to right across a period and decreases as you move down a group, with alkali metals being the most electropositive.
• 😀 Ionization energy increases as you move left to right across a period, as atoms become smaller and electrons are more tightly held.
• 😀 Ionization energy decreases as you move down a group because outer electrons are farther from the nucleus and are less tightly bound.
• 😀 Electron affinity tends to increase across a period and decrease down a group. Elements like fluorine and chlorine have high electron affinities.
• 😀 Fluorine is the most electronegative element, making it very effective at attracting electrons in a chemical bond.
• 😀 The atomic radius is a measure of an atom's size, determined by the distance from the nucleus to the outermost electron shell.
• 😀 Electronegativity refers to an element's ability to attract electrons in a bond, with higher values indicating stronger attraction.
• 😀 The trend of periodic properties like electronegativity, ionization energy, and atomic radius is essential for understanding chemical reactivity and bonding.
• 😀 Understanding periodic trends is important for exams like the ENEM, as it helps in predicting an element’s behavior in reactions.

Q & A

What are periodic properties in the context of the periodic table?

Periodic properties refer to characteristics of elements that repeat at regular intervals as you move across periods or down groups in the periodic table. These properties, such as atomic radius, electronegativity, and ionization energy, follow predictable patterns based on the position of the element.

How does the atomic radius change across a period and down a group?

The atomic radius decreases from left to right across a period because the nuclear charge increases, pulling electrons closer to the nucleus. It increases from top to bottom down a group as additional electron shells are added, making the atom larger.

What is the trend for electronegativity in the periodic table?

Electronegativity increases from left to right across a period and decreases from top to bottom down a group. This means elements on the right side of the periodic table are more likely to attract electrons in a chemical bond.

What is electropositivity and how does it change across the periodic table?

Electropositivity is a measure of an element's ability to lose electrons. It increases as you move from right to left across a period and from top to bottom down a group. Metals, which are electropositive, tend to lose electrons easily.

Why do noble gases not participate in regular chemical bonding?

Noble gases have a full valence shell, which makes them stable and unlikely to gain or lose electrons. As a result, they have very low electronegativity and do not form bonds easily.

How does ionization energy vary in the periodic table?

Ionization energy increases from left to right across a period and decreases from top to bottom down a group. Elements on the right side of the table have higher ionization energies because their electrons are closer to the nucleus and more tightly bound.

What is electron affinity and how does it change across periods and groups?

Electron affinity is the energy released when an atom gains an electron. It increases from left to right across a period and decreases from top to bottom down a group, as atoms with fewer electron shells can more easily accommodate an additional electron.

How do ionization energies differ between the first and second ionization energies?

The second ionization energy is always higher than the first because after the first electron is removed, the remaining electrons are held more tightly by the nucleus, making it harder to remove another electron.

What happens to the atomic radius and ionization energy as you go down a group?

As you go down a group, the atomic radius increases due to the addition of more electron shells. Ionization energy decreases because the outermost electrons are further from the nucleus and experience less attraction, making them easier to remove.

What is the relationship between electronegativity and electron affinity?

Electronegativity and electron affinity are related; elements with high electronegativity tend to have high electron affinity, as they are more likely to attract and gain electrons. Both properties increase across periods and decrease down groups.