Problem 52 - Chemistry Matter and Change

Question

Give the number of valence electrons in an atom of each element. a. cesium b. rubidium c. gallium d. zinc e. strontium

Step-by-Step Solution

Answer

The number of valence electrons for each element are: a. Cesium (Cs): 1 b. Rubidium (Rb): 1 c. Gallium (Ga): 3 d. Zinc (Zn): 2 e. Strontium (Sr): 2

Step 1: a. Cesium (Cs)

Cesium is in group 1 of the periodic table, which implies that it has only 1 electron in its outermost shell. Therefore, cesium has 1 valence electron.

Step 2: b. Rubidium (Rb)

Rubidium is also in group 1 of the periodic table, just like cesium. Therefore, rubidium has 1 valence electron as well.

Step 3: c. Gallium (Ga)

Gallium is in group 13 of the periodic table, which means it has 3 valence electrons (group number - 10).

Step 4: d. Zinc (Zn)

Zinc is in group 12 of the periodic table, which means it has 2 valence electrons (group number - 10).

Step 5: e. Strontium (Sr)

Strontium is in group 2 of the periodic table, which means it has 2 valence electrons. In summary, the number of valence electrons for each element are: a. Cesium: 1 b. Rubidium: 1 c. Gallium: 3 d. Zinc: 2 e. Strontium: 2

Key Concepts

Periodic Table

The periodic table is an organized chart of chemical elements, arranged in order of increasing atomic number. Each element is placed in a specific location due to its atomic structure, which includes the number of protons, electrons, and neutrons.
The structure of the periodic table is designed to clearly display the recurring chemical properties of the elements. This can be seen in the vertical columns called "groups" and horizontal rows called "periods."
Elements in the same group often have similar valence electron configurations, which leads to similar chemical behaviors.

Electron Configuration

Electron configuration is a way to describe the distribution of electrons in an atom's electron shells. This is based on quantum mechanical principles and helps determine how an element interacts with others.
To write the electron configuration, electrons are filled into different subshells according to a defined set of rules, known as the Aufbau principle.

• The first two electrons enter the s subshell of the first shell.
• Next electrons are placed into the 2s subshell, then 2p, and so on, following the order of increasing energy levels.

Understanding electron configuration helps predict elements' chemical and physical properties, as well as their placement on the periodic table.

Group Number

The group number in the periodic table is a fundamental concept for identifying elements' behavior and properties. Groups are the vertical columns that organize elements by similar valence electron configurations and corresponding chemical characteristics.
For instance, elements in Group 1, like cesium and rubidium, typically have 1 valence electron. Group 2 elements, such as strontium, have 2 valence electrons.
Knowing the group number is especially useful when determining the valence electrons of elements, as it indicates their likely chemical reactivity and bonding patterns with other elements.

Outer Shell Electrons

Outer shell electrons, often referred to as valence electrons, are the electrons located in the outermost shell of an atom. These electrons play a critical role in chemical reactions and bonding, as they are the most accessible to other atoms.
Each element has a characteristic number of valence electrons based on its electron configuration and position in the periodic table.

• For example, elements in Group 1, such as cesium, have 1 valence electron.
• Those in Group 13, like gallium, possess 3 valence electrons.
• The reactivity of an element is largely dictated by these outer shell electrons, which determine how easily an element will gain, lose, or share electrons in reactions.

Understanding outer shell electrons aids in predicting the chemical behavior of different elements.