Question

How many valence electrons are in each element? (a) \(\mathrm{Ba}\) (b) \(\mathrm{Al}\) (c) \(\mathrm{Be}\) (d) Se

Short answer

Ba has 2 valence electrons, Al has 3 valence electrons, Be has 2 valence electrons, and Se has 6 valence electrons.

Step-by-step solution

Understanding Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom that can participate in the formation of chemical bonds. The number of valence electrons for elements in the main groups of the periodic table can be determined by their group number.

Determine Valence Electrons for Barium (Ba)

Barium (Ba) is in Group 2 of the periodic table, which means it has 2 valence electrons.

Determine Valence Electrons for Aluminum (Al)

Aluminum (Al) is in Group 13 of the periodic table, but for purposes of counting valence electrons, it is considered to have 3 valence electrons (the '3' from the group number 13).

Determine Valence Electrons for Beryllium (Be)

Beryllium (Be) is also in Group 2 of the periodic table, so it has 2 valence electrons.

Determine Valence Electrons for Selenium (Se)

Selenium (Se) is in Group 16 of the periodic table. For the main group elements, the number of valence electrons is the group number minus 10, so selenium has 6 valence electrons (16 - 10 = 6).

Key concepts

Understanding the Periodic Table and Valence Electrons

The periodic table isn't just a colorful wall chart seen in every chemistry classroom; it's an invaluable tool for predicting an element's behavior by its position. For starters, it's organized into rows (periods) and columns (groups), with elements in the same column sharing similar properties.

Take valence electrons, for instance - the number of electrons found in an atom's outermost shell, which are vital in forming chemical bonds. Generally, elements in the main group (the 'A' groups, or groups 1-2 and 13-18 in the modern IUPAC numbering) have the same number of valence electrons as their group number. However, there's one small twist: for groups beyond 12, you'll want to subtract 10 from the group number to find the count of valence electrons. So, identifying valence electrons becomes as simple as locating which group the element falls under on the periodic table.

Chemical Bonds and the Role of Valence Electrons

Why fuss about valence electrons? Because they're the key players in the formation of chemical bonds, which are the glue holding atoms together in molecules. There are several types of chemical bonds, including ionic, covalent, and metallic bonds, each with unique features and depending largely on the valence electrons' interaction.

For instance, in ionic bonds, valence electrons are transferred from one atom to another, leading to a bond between oppositely charged ions. In covalent bonds, valence electrons are shared between atoms to fill their outer shells, forming a strong bond. Metallic bonds, on the other hand, involve a 'sea' of delocalized valence electrons shared across a lattice of metal cations. So, understanding valence electrons does more than just fulfill a homework question; it lays the groundwork for understanding how elements combine and interact in myriad ways to form the compounds all around us.

Electron Configuration and Predicting Valence Electrons

Electron configuration paints a picture of where an element's electrons are within its 'electron shells' and even more specifically, its orbitals. It's like a roadmap of electrons, and knowing how to read this map is critical for predicting an element's chemical behavior. The most stable (and thus most common) electron configurations are those where valence shells are either completely full or empty.

To determine valence electrons from electron configuration, look at the highest 'n' value (this refers to the principal quantum number indicating the most distant electron shell from the nucleus). For the main group elements, the number of electrons in this outer shell is the number of valence electrons. For elements in transitional and inner transitional layers, it's a bit more complex, but for now, just remember: valence electrons equal the outermost electrons depicted in the electron configuration, which directly affects an element's reactivity and type of bonds it can form.