Question

The column just before the stable noble gases are called the _________________. They have an outer

shell that needs just one more electron to be full.

Answer 1

The column just before the stable noble gases are called the halogens. They have an outer shell that needs just one more electron to be full.

Explanation

Halogens belong to Group 17 (formerly Group 7A) of the periodic table. They include elements like fluorine, chlorine, bromine, iodine, and astatine. These elements are highly reactive due to having seven electrons in their outer shell, needing only one more to achieve a stable configuration of eight electrons, similar to the noble gases. This makes them eager to gain an extra electron by forming ionic or covalent bonds with other elements.

Their reactivity decreases down the group due to an increase in atomic size and a decrease in electronegativity. Fluorine, at the top of the group, is the most reactive halogen, while iodine and astatine, towards the bottom, are less reactive.

Halogens exhibit diverse properties: fluorine is a pale yellow gas, chlorine is a greenish-yellow gas, bromine is a reddish-brown liquid, iodine is a shiny black solid, and astatine is a radioactive element. Their ability to form compounds with metals, create acids, and their use in various applications, from disinfectants to pharmaceuticals, highlights their significance in both industrial and biological contexts.

Answer 2

The column just before the stable noble gases are called the halogens. They have an outer shell that needs just one more electron to be full.

Step-by-step explanation:

The elements in the column just before the stable noble gases, specifically in Group 17 of the periodic table, are known as halogens. These elements include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The reason they are called halogens is derived from the Greek words "halo," meaning "salt," and "genes," meaning "forming." Halogens exhibit a characteristic of requiring only one more electron to achieve a full outer shell configuration, making them highly reactive.

In chemical terms, the outermost electron shell of halogens contains seven electrons, and to achieve a stable, full outer shell (like the noble gases), they need one more electron. This is because a full outer shell generally consists of eight electrons, following the octet rule.

For example, fluorine (F) has the electron configuration 1s² 2s² 2p⁵, with seven electrons in its outer shell. By gaining one more electron, fluorine achieves a stable configuration similar to neon (Ne), which has a full outer shell with eight electrons (1s² 2s² 2p⁶).

The tendency of halogens to gain an electron and achieve a stable electron configuration makes them highly reactive, particularly in forming compounds with elements that can readily lose electrons. This characteristic behavior is fundamental to the chemical properties of halogens and is a key aspect of their role in various chemical reactions and compound formations.