class Atom {

	Atom(int id, ChemEl chemlEl, Fragment frag) {
		if (frag == null){
			throw new IllegalArgumentException("Atom is not in a fragment!");
		}
		if (chemlEl == null){
			throw new IllegalArgumentException("Atom does not have an element!");
		}
		this.frag = frag;
		this.id = id;
		this.chemEl = chemlEl;
		this.type =frag.getType();
	}

	  Atom(int id, ChemEl chemlEl, Fragment frag);
	  Atom(ChemEl chemlEl);

}