An unknown element is a highly reactive shiny metal. Based on these properties, which of the following is MOST likely true about this unknown element? A It is located in the same group as potassium and sodium. It is located in the same period as copper and silver. It is located in the same period as neon and helium. D It is located in the same group as chlorine and astatine.

## Step 1<br />The problem describes an unknown element as a highly reactive shiny metal. This description aligns with the properties of alkali metals, which are known for their high reactivity and shiny appearance.<br /><br />## Step 2<br />Alkali metals are located in Group 1 of the periodic table, which includes elements like potassium (K) and sodium (Na). These elements are known for their high reactivity and shiny appearance.<br /><br />## Step 3<br />The other options do not align with the properties of alkali metals. For example, elements in the same period as copper and silver (option B) are transition metals, which are not as reactive as alkali metals. Similarly, elements in the same period as neon and helium (option C) are noble gases, which are known for their lack of reactivity. Lastly, elements in the same group as chlorine and astatine (option D) are halogens, which are non-metals and not as reactive as alkali metals.