Those elements that are also is group II of the Periodic Table, namely Be, Mg, Sr, Ba and Ra.
The element that would have properties most similar to the new element would be an element that lies in the same group as the new element. Specifically, the element with the most similar properties will lie directly above or below that element in the group.
Neon (Ne) would have properties most like helium (He) because they are both noble gases in the same group of the periodic table, with similar electron configurations and chemical reactivity.
That would be the noble gases
Mg (magnesium)
the most important properties in an element is state at room tempreture
Mg (magnesium)
Mg (magnesium)
Strontium (Sr) would react most like calcium (Ca) because they are both in the same group (Group 2) of the periodic table and share similar chemical properties.
Mg (magnesium)
Ge Germanium
Calcium is an element that behaves most like magnesium due to their similar chemical properties. They are both alkaline earth metals, have similar reactivity, and form similar compounds.
Bromine is the element most like chlorine because they belong to the same group in the periodic table. They have similar chemical properties and react in similar ways with other elements.