2.10. Atomic Structure: Periodic Properties

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In unit 2.10 of our Chemistry e-book course for the ENEM test, we will address one of the most fundamental topics in Chemistry: Atomic Structure and Periodic Properties. This is a topic that requires a solid understanding, as it is the basis for many other concepts and theories in Chemistry.

Atoms are the smallest particles of an element that retain the properties of that element. They are composed of three main types of subatomic particles: protons, neutrons and electrons. Protons have a positive charge, neutrons have no charge, and electrons have a negative charge. The number of protons in an atom determines the atomic number of the element, while the sum of protons and neutrons gives the mass number.

Now, let's dive deeper into the Periodic Properties. The Periodic Table is an essential tool in Chemistry. It arranges elements in order of increasing atomic number and groups elements with similar properties together. There are several periodic properties, including atomic radius, ionization energy, electron affinity, and electronegativity.

The atomic radius is the distance from the nucleus of the atom to its electron boundary. In the Periodic Table, atomic radius generally decreases as we move from left to right along a period (row) and increases as we move down a group (column).

Ionization energy is the energy required to remove an electron from an atom in its gaseous state. Ionization energy generally increases as we move from left to right down a period and decreases as we move down a group. This is because atoms with more protons have a stronger pull on their electrons, making it harder to remove an electron.

Electronic affinity is the energy released when an atom in its gaseous state gains an electron. Electron affinity generally increases as we move from left to right across a period and decreases as we move down a group. However, there are several exceptions to this trend.

Electronegativity is a measure of an atom's tendency to attract a bonding pair of electrons. Electronegativity generally increases as we move from left to right down a period and decreases as we move down a group.

Understanding atomic structure and periodic properties is crucial to understanding Chemistry on a deeper level. These concepts provide the foundation for understanding how atoms interact with each other to form compounds and how these interactions affect the properties and behaviors of those compounds. Therefore, we hope you find this chapter informative and useful in your ENEM preparation.

In our next chapter, we will continue to explore Chemistry at a deeper level, discussing the concepts of chemical bonding and molecular structure. Stay tuned for more!

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132.11. Atomic Structure: Atomic Radius