Do all elements reflect light? I have learnt a few things that reflect light,but do all elements do?
My teacher has explained to me that most things reflect light,so I am still curious.
 A: The short answer is yes, all material reflects light. The long answer is that
there are exceptions to this rule, as well as tricks/cheats.
Long answer:
Any time propagation light (or any type of radiation) encounters a boundary for
an object that is different than the material the light is coming from, some
fraction of the light will be reflected from that surface. You can see this for
instance by looking for your reflection in an otherwise transparent window. For
simple geometries, this is known as the Fresnel reflection for flat
surfaces, Mie scattering for scattering from spheres, or Rayleigh
scattering for sub-wavelength particles.
The presence of optical reflection/scattering is an extremely general statement
that is due to the boundary conditions (i.e. geometry) that applies any time
there is some change in space from one place to another. This includes the
situation of light going from air to glass, but also applies in situations such
as when you have light in a vacuum encounters a single atom (i.e. this doesn't
just apply to the approximation of continuous matter).
Exceptions:
The first exception is that when light goes from one material to another (such
as from air to glass), the behavior of the light has to be different within the
two materials. For most materials we think of light traveling in (e.g. air,
vacuum, glass, water, etc…), this means that the optical index of
refraction must be different. More generally it's the wave impedence
that must be different between the two materials. Now it's possible to find two
different materials with identical optical indices. For instance the image
below (taken from this webpage) shows a glass rod partially immersed
inside an index matching oil. You can see the part of the glass rod that sticks
out of the oil into the air (because it reflects some of the light), but it
looks like the glass vanishes inside the liquid because there is no reflection
there.

This trick of using another material to change the reflection properties of
something is very useful. For instance eye-glasses usually come with an
anti-reflection coating that reduces the amount of reflection (i.e. glare)
from the lenses. How this is done is they add a thin layer of a material on top
of the glass that has an index of refraction halfway between the glass lens and
air. Then, as the light travels from air into the coating layer (or from
coating into the glass) there is still some reflection, but it is much smaller
than from the air straight into the lens. If you added many layers you could
decrease the reflection even more. In the limit of adding infinite layers (or
making the material change continuously), then you again can have no
reflections. This is the idea behind optical cloaks.
A: As a very simply answer I can say that every material that contains electrons (i.e. nearly everything in the daily-life) can reflect light.
A: "elements" is probably not what you actually mean. "Carbon" is an element, but it comes in diamond form as well as graphite. And the two definitely look different. 
For another example, consider oxygen and nitrogen. You usually encounter them as gases (where the atoms pair up to forn O2 and N2), and these gases don't reflect light - they're pretty transparent.
A: 
Do all elements reflect light?

The answer depends from the definition for light. On the Wikipedia page for light you can found:

In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not.

Using this definition than yes, all elements as well as all molecules, as well as solid bodies, liquides and gases reflect light.
The best way to prevent materials from emitting electromagnetic radiation is to cool the material down to nearly zero Kelvin and to protect the material from outer radiation. But first you can't remove all thermic energy from a material ans secondly you can't protect a material from the surrounding electromagnetic radiation (all isolations around will have a higher temperature and by this will radiate).
Some information read about Black bodies and about Black-body radiation.
