crossword puzzle

2. A positively charged particle located in the nucleus of an atom.
5. The smallest particle of an element that retains the properties of that element and can exist alone or combined.
6. The smallest particle of a substance with all its chemical properties, composed of atoms chemically bonded.
8. An atom or group of atoms with a net electrical charge due to loss or gain of electrons.
10. Mass The mass of an atom, generally the sum of protons and neutrons.
11. The force holding atoms together in molecules (e.g., covalent, ionic bonds).
14. State The lowest energy level of an atom.
15. Level Stable states of energy that electrons in an atom may occupy.
16. Pure substances made of only one type of atom, which cannot be broken down chemically.

1. Forms of the same element differing in the number of neutrons.
2. Table The tabular arrangement of elements ordered by atomic number, grouping those with similar properties.
3. A particle in the nucleus with mass similar to a proton but no charge.
4. Number The number of protons in the nucleus, defining the element.
7. A negatively charged elementary particle orbiting the nucleus.
9. A pure substance formed by chemically bonding two or more different elements.
12. The central part of an atom containing protons and neutrons, holding nearly all the atom's mass.
13. Fundamental particles that make up protons and neutrons.