Exercícios Resolvidos - PRÓTONS, ELÉTRONS, NÊUTRONS, CÁTIONS E ÂNIONS.

Summary

This lesson explains the concepts of protons, neutrons, electrons, and ions, focusing on their differences and how they affect the charge and mass of an atom or ion. The instructor walks through examples using iron (Fe) and calcium (Ca) ions, illustrating how ionization alters the number of electrons while the number of protons remains constant. The lesson also covers how to calculate the number of neutrons and how ions such as cations (positively charged) and anions (negatively charged) form based on electron loss or gain. The goal is to help students understand atomic structure and ion behavior.

Takeaways

• 😀 The script explains the difference between an atom and an ion, emphasizing that ions result from the imbalance of protons and electrons.
• 😀 It introduces two types of ions: cations (positive charge) and anions (negative charge). Cations have more protons than electrons, while anions have more electrons than protons.
• 😀 For the example of iron (Fe), the script highlights the change in the number of electrons in the ion states Fe²⁺ and Fe³⁺, while the number of protons remains constant.
• 😀 The main difference between Fe, Fe²⁺, and Fe³⁺ is the number of electrons, with Fe being neutral, Fe²⁺ losing two electrons, and Fe³⁺ losing three.
• 😀 The script provides a detailed explanation of how to calculate the number of protons, electrons, and neutrons using the periodic table and atomic mass.
• 😀 In the case of calcium (Ca²⁺), the script shows how the number of protons is equal to 20, and the number of electrons is adjusted according to the ion charge (18 electrons for Ca²⁺).
• 😀 The number of neutrons in calcium is calculated as the difference between atomic mass and the number of protons (40 - 20 = 20 neutrons).
• 😀 The importance of understanding the relationship between protons, electrons, and neutrons in both neutral atoms and ions is emphasized.
• 😀 The script explains that when a positive charge (cation) is present, it indicates the loss of electrons, while a negative charge (anion) indicates the gain of electrons.
• 😀 In an example from a UFAL exam, the script demonstrates how to determine the mass number and the number of protons and neutrons from a trivalent cation with 23 electrons and 30 neutrons.

Q & A

What is the difference between Fe, Fe²⁺, and Fe³⁺?

The difference lies in the number of electrons. Fe (neutral atom) has equal numbers of protons and electrons. Fe²⁺ has lost two electrons and thus has a +2 charge. Fe³⁺ has lost three electrons and has a +3 charge.

What is the definition of an ion?

An ion is an atom or molecule that has gained or lost electrons, resulting in a net charge. There are two types of ions: cations (positive charge) and anions (negative charge).

How do cations form and what is their charge?

Cations form when an atom loses electrons, resulting in a positive charge because the number of protons exceeds the number of electrons.

How do anions form and what is their charge?

Anions form when an atom gains electrons, resulting in a negative charge because the number of electrons exceeds the number of protons.

What is the atomic structure of a neutral iron atom (Fe)?

A neutral iron atom (Fe) has 26 protons and 26 electrons, balancing each other out to make the overall charge zero.

How do you calculate the number of neutrons in an atom?

The number of neutrons is calculated by subtracting the number of protons (atomic number) from the atomic mass. For example, in a neutral iron atom (Fe), the atomic mass is approximately 55.85, and the number of protons is 26, so the number of neutrons is around 30.

What is the significance of the charge on an ion?

The charge indicates the difference between the number of protons and electrons. A positive charge means the ion has more protons than electrons, while a negative charge means the ion has more electrons than protons.

What happens when an atom loses electrons?

When an atom loses electrons, it becomes a cation, with a positive charge due to having more protons than electrons.

How do you determine the number of protons and electrons in a Ca²⁺ ion?

For a Ca²⁺ ion, the atomic number (protons) is 20. Since the ion has a 2+ charge, it has lost two electrons, so it has 18 electrons. The number of neutrons is found by subtracting the atomic number from the atomic mass (40 - 20 = 20 neutrons).

What is the number of protons, electrons, and neutrons in a trivalent cation with 23 electrons and 30 neutrons?

In a trivalent cation with 23 electrons and 30 neutrons, the number of protons is 26 (since the ion has a +3 charge, the protons exceed the electrons by 3). The number of neutrons is 30, and the atomic mass is 56 (26 protons + 30 neutrons).