Cs and Na are solids in room temperature while F and Xe are gases.
The number of electrons in the outermost shell of an atom will determine its reactivity. Out of the gases given Xe and F, F ( the most electronegative element) posses 5 valence shell electrons which makes it highly reactive while Xe which is a noble gas posses 8 valence shell electrons which makes it less reactive compared to many elements.
She should make observations next. If she doesnt make observations, it would be difficult to form a hypothesis and design an experiment, the result will more likely to be inaccurate too.
Stems of Vascular plants are made of vascular tissues and lignin which gives it is characteristics stiffness and the ability to grow tall to access more light and air.
