Problem 117 Why is the periodic trend in ato... [FREE SOLUTION]

Chapter 7: Problem 117

Why is the periodic trend in atomic size opposite to the trend in ionization energy?

Short Answer

Expert verified

The periodic trends in atomic size and ionization energy are opposite because as atomic size decreases (due to an increase in nuclear charge) across a period, it becomes harder to remove electrons, therefore the ionization energy increases.

Step by step solution

Understanding Atomic Size

Atomic size refers to the distance from the nucleus to the outermost shell where the last electron resides. Across a period (left to right) in the periodic table, atomic size decreases. This is due to the increasing positive charge of the nucleus, which pulls electrons closer and reduces the size of the atom.

Understanding Ionization Energy

Ionization energy is the energy needed to remove an electron from an atom. As we move across a period in the periodic table, ionization energy tends to increase. The reason is associated with the increase in nuclear charge (protons) that attracts the electrons in the outermost shell more strongly, making it harder to remove these electrons.

Comparing Atomic Size and Ionization Energy

Now we can see why the trends are opposite: smaller atoms (those with large nuclear charge) hold their electrons more tightly and thus require more energy to ionize. In contrast, larger atoms (with smaller nuclear charge) hold their electrons less tightly and require less energy to ionize.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Ionization Energy

Ionization energy is a critical concept in understanding how atoms interact with each other and form bonds. It refers to the amount of energy required to remove an electron from an atom in its gaseous state. When an electron is removed, the atom becomes a positively charged ion.

Several factors influence ionization energy:

Atomic Size: Generally, the larger the atomic size, the lower the ionization energy. This is because electrons are further from the nucleus and experience less pull, making them easier to remove.
Nuclear Charge: A higher positive nuclear charge attracts electrons more strongly, increasing ionization energy.
Electron Shielding: Inner electrons can shield outer electrons from the full effect of the nucleus, affecting ionization energy.

As we move across a period in the periodic table, ionization energy tends to increase. This is because electrons are added to the same energy level while protons are added to the nucleus, increasing nuclear charge and reducing atomic size, which requires more energy to remove an electron.

Periodic Trends

The periodic table is structured such that elements are arranged by increasing atomic number and show patterns in their chemical behaviors.

Here are some important periodic trends:

Atomic Size: As you move from left to right across a period, atomic size generally decreases. Meanwhile, as you move down a group, atomic size increases because additional electron shells are added.
Ionization Energy: Ionization energy increases from left to right across a period, as atoms become smaller and hold onto their electrons more tightly.
Electronegativity: This is the ability of an atom to attract electrons. It typically increases across a period and decreases down a group.

Understanding these periodic trends helps explain the chemical reactivity and bonding behaviors of elements. For example, elements with low ionization energy tend to lose electrons easily and form positive ions, while those with high ionization energy tend to gain electrons.

Nuclear Charge

The concept of nuclear charge is vital to understanding the structure and behavior of atoms. Simply put, nuclear charge refers to the total charge of all the protons in the nucleus of an atom. Each proton carries a positive charge, so the more protons, the higher the nuclear charge.

Here's how nuclear charge affects atomic properties:

Atomic Size: As nuclear charge increases, the electrons are pulled closer to the nucleus, decreasing atomic size.
Ionization Energy: Higher nuclear charge means electrons are more strongly attracted to the nucleus, increasing ionization energy.
Electronegativity and Reactivity: Atoms with high nuclear charge are often more electronegative and can be more reactive, especially non-metals.

Nuclear charge plays a key role in why atoms of different elements exhibit unique properties and underlies the periodic trends seen across the periodic table.

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Why is the periodic trend in atomic size opposite to the trend in ionization energy?

Short Answer

Step by step solution

Understanding Atomic Size

Understanding Ionization Energy

Comparing Atomic Size and Ionization Energy

Key Concepts

Ionization Energy

Periodic Trends

Nuclear Charge

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