Question

According to the general trend, the ionization energy for a group of elements (increases/decreases) proceeding up a group in the periodic table.

Short answer

Ionization energy increases proceeding up a group in the periodic table.

Step-by-step solution

Understand Ionization Energy

Ionization energy is the energy required to remove an electron from a gaseous atom or ion. Higher ionization energy means more energy is needed to remove an electron.

Analyze Periodic Trends

In the periodic table, elements are arranged in groups and periods. Groups are the vertical columns, and periods are the horizontal rows. As you move up a group in the periodic table, there are several factors to consider, such as the atomic size and effective nuclear charge.

Atomic Size Factor

As you move up a group in the periodic table, the atomic size decreases because there are fewer electron shells. A smaller atomic size results in electrons being closer to the nucleus, which increases the attraction between the nucleus and the electrons.

Effective Nuclear Charge

As you move up a group, the effective nuclear charge experienced by an electron increases because there are fewer inner shell electrons to shield the outer electrons from the nucleus. This increased nuclear charge strengthens the hold on the electrons.

Conclusion on Ionization Energy Trend

Due to the smaller atomic size and increased effective nuclear charge, the ionization energy increases as you move up a group in the periodic table. This is because more energy is required to remove an electron that is held more tightly to the nucleus.

Key concepts

Atomic Size

Atomic size, sometimes referred to as atomic radius, is an important factor in understanding ionization energy. Simply put, atomic size describes how large an atom is. It is determined by how far the outermost electrons are from the nucleus.
In the periodic table, atomic size generally decreases as you move up a group. This is because, with each step upward, the number of energy levels, or shells, decreases. Fewer shells mean electrons are closer to the nucleus.
When electrons are closer, their attraction to the positively charged nucleus increases. This means the atom becomes "tighter," making it harder to remove an electron. So, the smaller the atomic size, the higher the ionization energy required to remove an electron.

• Atomic radius decreases as you move up a group.
• Atoms with fewer energy levels have electrons that are closer to the nucleus.
• With a smaller atomic size, ionization energy increases due to stronger attraction.

Effective Nuclear Charge

Effective nuclear charge describes the net positive charge experienced by an electron in a multi-electron atom. It's a concept used to explain why electrons in a larger atom aren't as tightly bound to the nucleus compared to smaller atoms.
As you move up a group in the periodic table, the effective nuclear charge felt by the outer electrons generally increases. The reason? With fewer inner electron shells to shield these outer electrons, the strong positive charge of the protons in the nucleus pulls at them more strongly.
This becomes significant toward understanding ionization energy. With the electrons being more tightly bound due to a higher effective nuclear charge, it requires more energy to remove one of these electrons from the atom.

• Fewer inner-shell electrons result in higher effective nuclear charge.
• Strong nuclear pull makes electrons harder to remove.
• Increased effective nuclear charge correlates with higher ionization energy.

Periodic Trends

Understanding periodic trends is key to predicting the behavior of elements in the periodic table, such as their ionization energy. Periodic trends are patterns that arise from the arrangement of elements in the table, and they are influenced by atomic structures.
When it comes to ionization energy, these trends show a general increase as you move up a group. This is mainly due to changes in atomic size and effective nuclear charge. As discussed earlier, smaller atoms have electrons that are closer to the nucleus, and a higher effective nuclear charge makes it more difficult to remove these electrons.
Aside from the upward trend, ionization energy also generally increases across a period, but that's a topic for another time. Right now, it's important to focus on the vertical movement in groups. Remember these core ideas of atomic size shrinking and effective nuclear charge strengthening to better understand the trend in ionization energy.

• Ionization energy increases up a group.
• Factors include shrinking atomic size and increased nuclear charge.
• Understanding these trends helps in predicting element behavior.