Problem 90 - General Chemistry: Principles and Modern Applications

Question

Give the symbol of the element (a) in group 14 that has the smallest atoms; (b) in period 5 that has the largest atoms; (c) in group 17 that has the lowest first ionization energy.

Step-by-Step Solution

Answer

The element with the smallest atoms in group 14 is Carbon (C), the element with the largest atoms in period 5 is Xenon (Xe), and the element with the lowest first ionization energy in group 17 is Astatine (At).

Step 1: Identifying the element in group 14 with the smallest atoms

Looking at group 14 on the periodic table, the elements are Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn) and Lead (Pb). Atomic size increases as one moves down the group in the periodic table. Hence, the element with the smallest atoms in group 14 is Carbon (C).

Step 2: Identifying the element in period 5 with the largest atoms

In period 5, the elements range from Rubidium (Rb) to Xenon (Xe). Generally, atomic size increases as one moves from left to right in a period on the periodic table. Therefore, the element with the largest atoms in period 5 is Xenon (Xe).

Step 3: Identifying the element in group 17 with the lowest first ionization energy

In group 17, the elements are Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At). Generally, ionization energy decreases as one moves down a group in the periodic table. Therefore, the element with the lowest first ionization energy in group 17 is Astatine (At).

Key Concepts

Atomic Size

The concept of atomic size refers to the size of an atom, typically measured by its atomic radius. As a general rule, the atomic size increases as you move down a group in the periodic table. This is because additional electron shells are added, making the atom larger.

Conversely, atomic size decreases as you move from left to right across a period. The increase in positive charge from the added protons in the nucleus pulls the electrons closer, reducing the atomic size. For instance, in group 14, the smallest atom is Carbon (C) because it is at the top of the group. By moving to period 5, the largest atom is Xenon (Xe) as it sits on the right, where atomic sizes increase again. Understanding this pattern helps predict other properties of elements.

Ionization Energy

Ionization energy is the energy required to remove an electron from a neutral atom. It serves as an important indicator of an atom's tendency to form positive ions. Typically, ionization energy increases across a period from left to right. This is due to the stronger attraction between the electrons and the nucleus as atomic number increases.

However, ionization energy decreases as you move down a group. As atomic size increases, the outer electrons are further away from the nucleus and are less tightly bound. In group 17, for example, Astatine (At) has the lowest ionization energy because its electrons are the farthest from the nucleus, making them easier to remove. Understanding these trends is vital when predicting an element’s reactivity and chemical behavior.

Element Groups

Element groups on the periodic table consist of elements with similar chemical properties. These groups are vertical columns in the table. Each group signifies elements with the same number of electrons in their outermost shell, which influences their chemical behavior.

Group 14, for instance, includes Carbon (C) to Lead (Pb). These elements are known for forming similar types of chemical bonds. Meanwhile, group 17 features Halogens, such as Fluorine (F) and Astatine (At). They are highly reactive due to needing only one electron to complete their outer shell. Recognizing these group patterns on the periodic table can help you predict the properties and reactivities of different elements, making complex concepts of chemistry much easier to grasp.