Chemistry Unit Vocabulary Terms
1.
Proton – positively charged subatomic particle found in the nucleus
2.
Neutron – neutral (no charge) subatomic particle found in the nucleus
3.
Electron – negatively charged subatomic particle found in the electron cloud
4.
Atom - the smallest particle of an element that still has the properties of that element
5.
Element - An element is a substance made up of only one kind of atom
6.
Atomic number – the number that identifies an element as the number of protons in the
nucleus
7.
Mass number - the mass of a specific isotope of an element (number of protons + number
of neutrons)
8.
Average mass - the weighted average of the mass numbers of all the isotopes of an
element. ( a.k.a. average atomic mass)
9.
Nucleus - dense core of an atom that carries a positive charge and composed protons &
neutrons
10. Electron cloud - a cloud of negative charge that surrounds the nucleus of an atom
composed of electrons.
11. Isotopes - Atoms of the same element with different numbers of neutrons
12. Metalloids or semi-metallics or semi-conductors – elements the have properties of both
metals & non metals that are found along the stair step that divides the periodic table
13. Transition metals – mildly reactive metal elements located in the “B” groups or 3-12
14. Alkali metals – very reactive metal elements located in group 1A or 1
15. Alkaline earth metals – active metal elements located in group 2A or 2
16. Noble gases – inert (non reactive) gas elements located in group 8A or 18
17. Halogens – very active nonmetallic elements located in group 7A or 17
18. Metals – elements having 3 or fewer electrons in their outer energy level
19. Nonmetals – elements having 5 or more electrons in their outer energy level
20. Periodic Table Group or Family – the elements in a column on the periodic table. The
group number relates the number of valence electrons in each of the elements in the
group
21. Periodic Table Period - the elements in a row on the periodic table. The period number
gives the number of energy levels of the elements in that period.