nobleGas.cs

using System;

public class Program
{
    public static void Main()
    {
        NobleGas argon = new NobleGas("Argon", "Ar", 18);
        argon.Describe();
    }
	
    public class Element
    {
        public string Name { get; set; }
        public string Symbol { get; set; }
        public int Number { get; set; }

        public Element(string name, string symbol, int number)
        {
            this.Name = name;
            this.Symbol = symbol;
            this.Number = number;
        }

        public virtual void Describe()
        {
            Console.WriteLine
            (
                "{0} ({1}) has atomic number {2}.",
                this.Name, this.Symbol, this.Number
            );
        }
    }
	
    public class NobleGas : Element
    {
        public string Category { get; set; }
        public string Type { get; set; }
        public string Reactivity { get; set; }
	    
        public NobleGas(string name, string symbol, int number) : base(name, symbol, number)
        {
            this.Category = "gas";
            this.Type = "noble gas";
            this.Reactivity = "low";
        }
	    
        public override void Describe()
        {
            Console.WriteLine
            (
                "{0} ({1}; {2}) is a {3} of type {4}. It has {5} reactivity.", 
                this.Name, this.Symbol, this.Number,
                this.Category, this.Type, this.Reactivity
            );
        }
    }
}