Which of the following statements is true about Group 1 elements?

Group 1 elements, also known as alkali metals, are characterized by their shiny appearance and their tendency to oxidize quickly when exposed to air. This rapid oxidation occurs because these metals have a single electron in their outermost shell, which they readily lose to achieve a stable electronic configuration. This loss of the outer electron leads to the formation of positive ions.

The shininess of these metals is due to their metallic luster, and the quick oxidation demonstrates their high reactivity, particularly with oxygen and moisture in the air. This is a defining trait of alkali metals, setting them apart from other groups in the periodic table.

The other options reflect common misconceptions about Group 1 elements. While they are not noble gases, noble gases belong to Group 18 of the periodic table and are well-known for their lack of reactivity. The statement about decreasing reactivity down the group is also inaccurate; it’s actually the opposite, as reactivity increases down the group due to the weakening of the attraction between the outermost electron and the nucleus. Lastly, forming ions with a -1 oxidation state is incorrect, as alkali metals typically form ions with a +1 oxidation state when they lose their single outer electron.