horizontal row in the periodic table

smallest part of an element that still retains the properties of the element

weighted average mass of the mixture of an elements’ isotopes

neutral particle composed of quarks inside the nucleus of an atom

Positively charged center of an atom that contains protons and neutrons and is surrounded by a cloud of electrons

vertical column in the periodic table

particle composed of quarks inside the nucleus of an atom that has a charge of 1+

 organized list of all known elements that are arranged in increasing atomic number and by changes in chemical and physical properties

particle surrounding the center of an atom that have a charge of -1

 uses the symbol for an element and dots representing the number of electrons in the element’s outer energy level

 number of protons in an atom’s nucleus