Question

How many electrons must be gained or lost for the following to achieve a noble gas electron configuration? (a) a potassium atom (b) an aluminum ion (c) a bromine atom (d) a selenium atom

Short answer

Potassium must lose one electron; aluminum ion (assuming it's Al^3+) has already lost three electrons; bromine must gain one electron; selenium must gain two electrons.

Step-by-step solution

Find the Nearest Noble Gas Configuration for Potassium

Identify the noble gas that is closest to potassium (K) in the periodic table without going over its atomic number. Potassium, with an atomic number of 19, would need to lose one electron to achieve the noble gas electron configuration of Argon (Ar), which has 18 electrons.

Determine the Charge of Aluminum Ion

Aluminum (Al) normally forms a +3 ion by losing three electrons. Therefore, an aluminum ion has already lost three electrons in order to have a noble gas configuration similar to Neon (Ne), which has 10 electrons.

Ascertain How Bromine Achieves Noble Gas Configuration

Bromine (Br), with an atomic number of 35, requires one additional electron to achieve the noble gas electron configuration of Krypton (Kr), which has 36 electrons.

Determine Electrons for Selenium to Reach Noble Gas Configuration

Selenium (Se) has an atomic number of 34. It needs to gain 2 electrons to reach the noble gas configuration of Krypton (Kr), which has 36 electrons.

Key concepts

Electron Gain and Loss

Understanding how elements gain or lose electrons is essential to chemistry, especially when discussing noble gas electron configurations. Atoms often become more stable when they achieve a full outer electron shell similar to that of noble gases.

For instance, a potassium (K) atom will lose one electron to attain the stability that Argon (Ar) possesses, reflecting a full outer shell. In contrast, a bromine (Br) atom, friendlier to electron addition, gains an electron to mirror the stability of Krypton (Kr).

Simplifying these concepts aids students in recognizing patterns of electron transfer and understanding the underlying rules governing reactions and bonding in chemistry.

Periodic Table

The periodic table is a map of the chemical elements that serves as a key reference for understanding electron configuration. It's structured so that elements with similar chemical behaviors are aligned in columns known as 'groups' and the progressively increasing atomic number goes from left to right in 'periods'.

The magic of the periodic table lies in its predictive power. Looking at the table, one can predict the electron loss or gain needed for an element to achieve a noble gas configuration, just as in the case of potassium losing an electron or bromine gaining one.

Atomic Number

The atomic number of an element is a fundamental characteristic that tells us the number of protons in the nucleus of an atom. It also indirectly informs us about the number of electrons in a neutral atom, as the number of electrons equals the number of protons.

For example, selenium (Se) has an atomic number of 34, signifying 34 electrons in its neutral state. This number not only helps in the identification of an element but also guides us during ion formation and the quest for noble gas configurations.

Ion Formation

Transitioning from atoms to ions, ion formation is a crucial concept in chemistry. It involves atoms gaining or losing electrons, which results in a net charge. A positive ion, known as a cation, is formed from electron loss as seen with aluminum (Al), which loses three electrons to achieve stability.

Conversely, an anion is created from electron gain, like when selenium (Se) gains two electrons. Acknowledging ion formation is key to understanding chemical reactivity and the penchant for substances to combine, and ultimately guiding students towards mastering how elements bond to form more complex compounds.