GRANDEZAS ATÔMICAS

Summary

In this video, Professor Marcos discusses atomic quantities and their importance in understanding chemistry, particularly for high school students and those preparing for entrance exams. The lecture covers key atomic properties such as atomic mass, atomic number, protons, neutrons, and electrons, explaining their relationships and significance. The professor also delves into ions, cations, and anions, and how atoms can gain or lose electrons to form these charged species. The lesson includes practical examples, representations of elements, and a review of how these concepts are applied in chemical reactions. The session emphasizes the foundational nature of these concepts for deeper studies in chemistry.

Takeaways

• 😀 Atoms consist of protons, neutrons, and electrons, with protons and neutrons located in the nucleus and electrons orbiting around it in the electron cloud.
• 😀 The atomic number (Z) is equal to the number of protons in an atom and determines the identity of the element.
• 😀 The mass number (A) is the sum of protons and neutrons in an atom, and it's a key indicator of the atom's mass.
• 😀 The number of protons and electrons are always equal in a neutral atom, making the atom electrically neutral.
• 😀 If an atom gains or loses electrons, it becomes an ion: a cation (positive charge) if it loses electrons, or an anion (negative charge) if it gains electrons.
• 😀 The mass of the electron is negligible compared to the mass of protons and neutrons, which are considered to contribute the majority of the atom's mass.
• 😀 The periodic table lists elements with their atomic number (Z) and atomic mass (A). The atomic number is shown above the element's symbol, and the atomic mass is typically shown below it.
• 😀 In ionic forms, the number of protons and electrons is no longer equal. For example, a calcium ion (Ca²⁺) has lost two electrons.
• 😀 The number of neutrons in an atom can be calculated by subtracting the atomic number from the atomic mass (A - Z = number of neutrons).
• 😀 The electron configuration in an atom can change when an atom gains or loses electrons, affecting its charge and behavior in chemical reactions.

Q & A

What are the main atomic quantities discussed in the lecture?

The lecture discusses five atomic quantities: atomic mass, number of protons, atomic number, number of electrons, and number of neutrons.

How are the number of protons and atomic number related?

The number of protons and atomic number are always equal and serve as the identity of the element. The number of protons defines which element an atom is.

What is the relationship between protons, neutrons, and electrons in an atom?

In a neutral atom, the number of protons is equal to the number of electrons. Neutrons contribute to the atomic mass but do not affect the atom's charge.

What happens when an atom loses or gains electrons?

When an atom loses electrons, it becomes a cation (positively charged). When it gains electrons, it becomes an anion (negatively charged).

What is the mass number of an element, and how is it determined?

The mass number is the sum of the number of protons and neutrons in an atom. It determines the atom's overall mass and is typically displayed on the periodic table.

How are atomic symbols used to represent elements?

Atomic symbols show the element’s symbol, atomic number (number of protons), and mass number. For example, in a symbol like ¹⁹₉F, 19 is the mass number, and 9 is the atomic number.

How is the number of neutrons calculated for an atom?

The number of neutrons can be calculated by subtracting the atomic number (number of protons) from the mass number. For example, if the mass number is 19 and the atomic number is 9, the number of neutrons is 10.

What is the significance of the atomic number?

The atomic number determines the identity of the element and is equal to the number of protons in an atom. It also helps identify the number of electrons in a neutral atom.

How does the charge of an ion relate to the number of protons and electrons?

The charge of an ion is determined by the difference between the number of protons and electrons. If there are more protons than electrons, the ion is positively charged (cation). If there are more electrons than protons, the ion is negatively charged (anion).

What happens to the number of electrons in an ion compared to a neutral atom?

In an ion, the number of electrons is different from that in a neutral atom. For cations, the number of electrons is less than the number of protons. For anions, the number of electrons is greater than the number of protons.