Solve these clues to fill the grid.
- State of matter that fills any space, like air
- 2 Across
- Center of an atom or a cell
- 4 Across
- An elementary particle with negative charge
- 9 Across
- One of two or more atoms with the same atomic number but with different numbers of neutrons
- 11 Across
- The order of an element in Mendeleyev's table of the elements
- 14 Across
- The smallest component of an element having the chemical properties of the element
- 15 Across
- A chemical ___ in which one atom loses an electron to form a positive ion and the other atom gains
- 16 Across
- How much matter something contains
- 1 Down
- How tightly packed the matter in something is
- 3 Down
- An abstract part of something
- 5 Down
- A chemical ___ that involves sharing a pair of electrons between atoms in a molecule
- 6 Down
- A substance consisting of two or more substances mixed together
- 7 Down
- A fourth state of matter distinct from solid or liquid or gas and present in stars and fusion
- 8 Down
- How loud something is, or how much space it fills
- 10 Down
- A substance formed by chemical union of two or more elements or ingredients in definite proportion
- 12 Down
- State of matter that flows like water
- 13 Down