Never found in nature uncombined?
Alkali metals
Alkaline Earth Metals
Boron Family
Carbon Family
Nitrogen Family
Oxygen Family
Halogen Family
Noble Gases
See answer to same question posted later
The elements listed here, including the alkali metals, alkaline earth metals, boron family, carbon family, nitrogen family, oxygen family, halogen family, and noble gases, are never found in nature uncombined.
To determine this, we can use the periodic table and some knowledge of chemical reactivity.
First, let's define "uncombined." In the context of elements found in nature, uncombined means that the element is not chemically bonded with other elements. This means it is in its pure form as an individual atom or molecule.
Using the periodic table, we can determine the reactivity of elements by their position. The elements on the left side of the periodic table, such as the alkali metals (Group 1: lithium, sodium, potassium, etc.) and alkaline earth metals (Group 2: beryllium, magnesium, calcium, etc.), are highly reactive due to having one or two valence electrons. They readily react with other elements to form compounds, so we rarely find them uncombined in nature.
Moving towards the right side of the periodic table, we have the boron family (Group 13: boron, aluminum, gallium, etc.), carbon family (Group 14: carbon, silicon, germanium, etc.), nitrogen family (Group 15: nitrogen, phosphorus, arsenic, etc.), oxygen family (Group 16: oxygen, sulfur, selenium, etc.), and halogen family (Group 17: fluorine, chlorine, bromine, etc.). These elements also tend to be highly reactive and readily form compounds, making their uncombined forms rare in nature.
Finally, we have the noble gases (Group 18: helium, neon, argon, etc.), which are known for their extremely low reactivity. They have full valence electron shells, making them stable and unlikely to form compounds. Hence, noble gases are never found uncombined in nature.
So, by analyzing the periodic table and understanding the reactivity of elements, we can determine that the elements listed in your question are never found in nature uncombined.