To determine which of the given elements is a metal, we need to understand the classification of each element based on their properties.
- Hafnium [tex]$(Hf)$[/tex]: Hafnium is a chemical element with the symbol Hf and atomic number 72. It belongs to the transition metals category. Transition metals are known for their ability to conduct electricity and heat, as well as their malleability. Therefore, hafnium is classified as a metal.
- Radon [tex]$(Rn)$[/tex]: Radon is a chemical element with the symbol Rn and atomic number 86. It is a noble gas and is typically found in a gaseous state. Noble gases are known for their lack of reactivity and are nonmetals. Hence, radon is not a metal.
- Silicon [tex]$(Si)$[/tex]: Silicon is a chemical element with the symbol Si and atomic number 14. It is classified as a metalloid, which means it has properties intermediate between metals and nonmetals. It is widely used in semiconductors. Silicon is not strictly a metal.
- Sulfur [tex]$(S)$[/tex]: Sulfur is a chemical element with the symbol S and atomic number 16. It is a nonmetal known for its distinct yellow color and its usage in various chemical processes. Therefore, sulfur is not a metal.
- Selenium [tex]$(Se)$[/tex]: Selenium is a chemical element with the symbol Se and atomic number 34. Similar to silicon, it is categorized as a metalloid, possessing properties of both metals and nonmetals. Selenium is not classified as a metal.
Given the classifications, the element among the choices that is a metal is:
A. Hafnium [tex]$(Hf)$[/tex]
Therefore, the correct answer is option 1: Hafnium [tex]$(Hf)$[/tex].
