Question

How many valence electrons are in each element? (a) \(\mathrm{O}\) (b) \(\mathrm{S}\) (c) \(\mathrm{Br}\) (d) \(\mathrm{Rb}\)

Short answer

The number of valence electrons: (a) Oxygen (O) - 6, (b) Sulfur (S) - 6, (c) Bromine (Br) - 7, (d) Rubidium (Rb) - 1.

Step-by-step solution

Understanding Valence Electrons

Valence electrons are the outermost electrons of an atom and are involved in chemical reactions and bonding. To determine the number of valence electrons for an element, one can refer to the element's group number in the periodic table. Elements in the same group typically have the same number of valence electrons.

Finding Valence Electrons for Oxygen (O)

Oxygen is in Group 16 (or VI A) of the periodic table. Elements in Group 16 have 6 valence electrons. Therefore, Oxygen (O) has 6 valence electrons.

Finding Valence Electrons for Sulfur (S)

Sulfur is also in Group 16 (or VI A) of the periodic table. Hence, like Oxygen, Sulfur (S) also has 6 valence electrons.

Finding Valence Electrons for Bromine (Br)

Bromine is in Group 17 (or VII A) of the periodic table. Elements in Group 17 have 7 valence electrons. Therefore, Bromine (Br) has 7 valence electrons.

Finding Valence Electrons for Rubidium (Rb)

Rubidium is in Group 1 (or I A) of the periodic table. Elements in Group 1 have 1 valence electron. Therefore, Rubidium (Rb) has 1 valence electron.

Key concepts

Understanding Periodic Table Groups

The Periodic Table is more than just a list of elements; it's a comprehensive chart that categorizes the elements based on shared properties and behaviors. One of the most critical layouts in the Periodic Table is the division into 'groups'. These are the columns that run vertically. Each group contains elements with the same number of valence electrons, which are paramount in predicting how an element will react chemically.

For instance, Group 1 elements, known as the alkali metals, all have one valence electron. This makes them highly reactive, especially with water, as they seek to lose that single electron to achieve a more stable electron configuration. Similarly, elements in Group 17, the halogens, have seven valence electrons and typically gain one electron to complete their outer shell. Understanding the group patterns can dramatically improve a student's ability to predict the types of chemical reactions an element might engage in.

Electron Configuration and Its Role in Chemistry

Electron configuration is the term used to describe the distribution of electrons in an atom's orbitals. It is the key to unlocking an element's chemical behavior. The valence electrons, which occupy the outermost shell, are particularly important because they can be lost, gained, or shared during chemical reactions.

To intuitively comprehend an element's electron configuration without memorizing complex tables, you should understand that electrons fill orbitals in a way that minimizes the energy of the atom. This approach starts from the simplest orbitals (1s) and moves towards more complex ones. For example, Oxygen with an atomic number of 8 has an electron configuration expressed as 1s² 2s² 2p⁴, which indicates that oxygen has 6 electrons in its outermost shell, corresponding to its position in Group 16.

Chemical Reactions and Valence Electrons

Chemical reactions are the bread and butter of chemistry, involving the breaking and forming of bonds between atoms. Valence electrons play the starring role in these processes. They are the electrons available for bonding, and their number and arrangement determine an element's chemical reactivity and the types of bonds it can form.

During chemical reactions, elements strive to reach a state of maximum stability, often achieved by having a full valence shell of electrons, known as the octet rule. For instance, in sodium chloride (table salt), sodium (a Group 1 element) donates its single valence electron to chlorine (a Group 17 element), which needs one more electron to complete its valence shell. Exploring how valence electrons guide the interactions between elements can demystify the mechanisms of many chemical reactions, from the synthesis of salts to the complexities of organic chemistry.