| A | B |
|---|
| atom | the smallest part of an element |
| atomic number | the number of protons in the nucleus of each atom |
| atomic mass | the mass of an element; nearly equal to the number of protons and neutrons found in the element's nucleus |
| electron | an invisible, negatively charged particle that travels around the nucleus of an atom |
| electron cloud | the area surrounding the nucleus of an atom where electrons arelikely to be found |
| element | a substance made up of only one kind of atom that cannot be divided by ordinary chemical means |
| energy level | the different positions and specific amount of an electron's energy |
| isotopes | atoms that are the same element that have different numbers of neutrons but he same number of protons |
| mass number | the sum of the number of protons and meutrons in an atom of an element |
| matter | the term used to describe anything that has mass and takes up space |
| molecule | the smallest part of a compound that still has the properties of the compound |
| neutron | an uncharged particle located in the nucleus of an atom |
| nucleus | the positively charged, central part of an atom |
| periodic table | a chart that organizes the elements by the number of protons in each element's nucleus |
| proton | a postively charged particle in the nucleus of an atom |
| state of matter | the lhysical forms in which a substance can exist: solid, liquid, gas, and plasma |
