1.
the basic building block of matter
2.
the quantity of matter contained in an atom of an element
3.
a unit of mass used to describe matter at the atomic scale
4.
the number of protons in the nucleus of each atom of that element
5.
stream of electrons leaving the negative electrode in a discharge tube containing a gas at low pressure, or electrons emitted by a heated filament in certain electron tubes
6.
All matter is composed of extremely small particles called atoms
7.
a subatomic particle that is found in all atoms
8.
a column in the periodic table of the chemical elements
9.
atoms with the same number of protons but different numbers of neutrons
10.
the total number of protons and neutrons in an atom
11.
a subatomic particle found inside the nucleus of every atom
12.
the positively charged center of the atom, consisting of protons and neutrons
13.
a row of chemical elements
14.
organizes all discovered chemical elements in rows and columns according to increasing atomic number
15.
a subatomic particle with a positive electric charge
