There are many properties that can be used, and it depends on how you are planning to categorise the element. The simplest properties used are the density of the element, its colour and its physical state at standard temperature and pressure. More importantly is it a metal, or non-metal.
Better ways however are to look at its electronic configuration. There are simple and advanced ways of expressing the electronic configuration, and so it depends a bit on what you already know about elements and electronic configurations. The simplest way groups the electrons into shells and looks at the number of full shells to work out which row of the periodic table the element belongs to. The row it is in is one important way to classify an element.
You can also look at the number of outer electrons it has, as this is an important guide to which column of the periodic table the element belongs to, which is VERY important in classifying an element.
EG the halogens all have seven electrons in their outermost shell, the alkaline metals all have one outer electon, while the alkaline earths all have two outer electrons.
Better ways however are to look at its electronic configuration. There are simple and advanced ways of expressing the electronic configuration, and so it depends a bit on what you already know about elements and electronic configurations. The simplest way groups the electrons into shells and looks at the number of full shells to work out which row of the periodic table the element belongs to. The row it is in is one important way to classify an element.
You can also look at the number of outer electrons it has, as this is an important guide to which column of the periodic table the element belongs to, which is VERY important in classifying an element.
EG the halogens all have seven electrons in their outermost shell, the alkaline metals all have one outer electon, while the alkaline earths all have two outer electrons.
