Consciousness is Fundamental and Elemental
It's possible that David Chalmers came to the speculative conclusion that experience/consciousness is elemental and omnipresent because only that could satisfactorily explain (at least in part) the reality of experience/consciousness. In other words, if consciousness/experience is everywhere at all times, that that makes consciousness easier to explain. Thus, according to Sandra Blakeslee, Chalmers argues that “scientists need to come up with new fundamental laws of nature”.
Chalmers himself said:
"My approach is to think of conscious experience itself as a fundamental property of the universe. Thus the world has two kinds of information, one physical, one experiential. The challenge is to make theoretical connections between physical processes and conscious experience.” 
David Chalmers was also explicit about his position during a conference in 1994. This is how Barbara McKenna tells that story:
“Over the millennia scientists have concluded that there are a handful of elemental, irreducible ingredients in the universe--space, time, and mass, among them. At a national conference in 1994, philosopher David Chalmers proposed that consciousness also belongs on the list.” 
At first glance it's hard to even comprehend how consciousness/experience is (or could be) an elemental and fundamental aspect of the universe, on par with space, time, mass, etc.
In any case, Chalmers comes clean as to how philosophically massive it would be if experience or 'information' were seen to be everywhere. Chalmers himself says that
“[o]nce a fundamental link between information and experience is on the table, the door is opened to some grander metaphysical speculation concerning the nature of the world”.
Thus we aren't just talking philosophy of mind here; or even about the nature of human consciousness. We're essentially talking about ontology or some “grander metaphysical speculation”.
What and Where is Experience?
The first trick is to explain experience in terms of something else – something which isn't (initially) deemed to be experience. That something else is the processing of information.
Thus firstly Chalmers talks only in terms of processing. He tells us that “changes in experience correspond to changes in processing”. A process is itself seen as a functional property of the brain-mind. Thus if such mind-brain processes actually are experience (rather than causing experience), it follows that “any two functionally isomorphic systems must have the same sort of experiences”.
To recap. A mental process is a mental function and such functions determine – or actually are – experiences.
So what's being processed in the mind? According to Chalmers, it's “information” which also works as an “organizational property”.
Thus we can ask if experience is a functional process which is, as it were, getting to work on information; or is that getting to work itself information? Does information go in (as input) and only then do processes (therefore experience) make sense of that informational input? Or, at the least, is information the content of experience?
In fact Chalmers does talk about information as if it's input and not itself an aspect of the mind-brain. That is, input-as-information goes in, and then processing (therefore experience) follows. That's the case because Chalmers himself says that “experience is much more widespread than we might have believed, as information is everywhere”.
Thus not only is information external to the mind - so is experience. That's not a surprise as we've only just stated that experience is information.
To repeat. From the following, it would seem that “information processing” is experience because, to quote Chalmers in full, he says that
“[w]here there is simple information processing, there is simple experience, and where there is complex information processing, there is complex experience”.
Minds and Mental States
Chalmers also appears to make a strong distinction between minds and mental states. Every object or thing may not have a mind; though they may still have mental states. Or as Chalmers puts it:
“Instead, we can understand panpsychism as the thesis that some fundamental physical entities have mental states. For example, if quarks or photons have mental states, that suffices for panpsychism to be true, even if rocks and numbers do not have mental states. Perhaps it would not suffice for just one photon to have mental states.” 
Prima facie, it's hard to grasp the distinction between mental states and mind. That's not because I can't see the difference. It's because saying that a photon has a mental state is as problematic as saying that it has a mind.
The other problematic thing in Chalmers' quote above are the words “just one photon to have mental states”. Surely if one photon has mental states, then all photons must have mental states. Photons are fundamental and elementary enough as they are without saying one photon may have mental states and all the other photons may not. How could that be?
In any case, since Chalmers makes a distinction between mental states and minds, now we need to know what it means to say that, say, a photon has mental states. According to Chalmers, if photons have mental states, then
“there is something it is like to be a quark or a photon or a member of some other fundamental physical type”. 
From that one could say that photons can (or could) experience different qualia. Isn't it qualia, after all, that makes a mental state (or experience) “like something”?
Thus we've rejected minds and accepted mental states. And now it's said that some fundamental physical entities are conscious.
Firstly, what do the words “proto-experiential properties” mean? And how can we grasp the thought that such properties are “inside of the entities characterized by physics”?
Chalmers also introduces the term “phenomenal (or experiential) properties” . Qualia must constitute what it's like to be an object. Chalmers, on the other hand, says that
“phenomenal (or experiential) properties are properties characterizing what it is to be a conscious subject”.
It can now be said that the words “qualia” and “phenomenal properties” are virtual synonyms here since they appear to be playing the same role.
This leads to another point. Experience is made up of qualia. In that sense, a particular experience is a particular set of qualia. Or, at the least, an experience is made up of a given set of qualia, even if/though that set doesn't always exhaust that experience's content. (It's problematic to talk about a single experience when, like William James's “stream of consciousness', we may actually have a constant stream of experiences, none of which are discrete and neatly circumscribed.)
Either way, it's such qualia or phenomenal properties which problematise physicalism/materialism. After all, if we are physicalists then we must believe (as Chalmers puts it) that “all phenomenal truths [must be] grounded in microphysical truths”.
Chalmers, David. (2013) 'Panpsychism and Panprotopsychism'.(2010) The Character of Consciousness.
McKenna, Barbara. (1997) 'UCSC Review Winter 1997'.