| A | B |
|---|
| atom | smallest particle in an element |
| electrons | negatively charged subatomic particles; found in the electron cloud |
| nucleus | central core of an atom; made of protons and neutrons |
| energy level | specific amount of energy an electron has; number is the same as period number; makes up the electron cloud |
| neutron | subatomic particle with no electrical charge; found in the nucleus |
| atomic number | number of protons in an atom |
| isotopes | atoms with the same number of protons but a different number of neutrons |
| mass number | sum of protons and neutrons; whole number; not found on the PTOE |
| atomic mass | average mass of all the isotopes of an element; decimal number found on the PTOE |
| periodic table | chart of elements showing the repeating pattern of their properties |
| period | horizontal row on the PTOE that contains a series of different elements |
| group | also known as families; vertical column of PTOE;elements have same number of valence electrons |
| chemical symbol | one or two letter representation of an element; first letter is capitalized; second letter is not capitalized |
| plasma | state of matter that consists of a gas-like mixture of free electrons and nuclei of atoms that have been stripped of electrons |
| nuclear fusion | process in which two atomic nuclei combine, forming a larger nucleus and releasing huge amounts of energy |
| metal | shiny, malleable, ductile elements that are good conductors and tend to lose or share electrons in chemical reactions |
| malleable | element that can be hammered or rolled into flat sheets or other shapes |
| ductile | element that can be pulled out, or drawn, into long wire |
| conductivity | ability of an object to transfer heat or electricity to another object |
| reactivity | ease and speed with which an element combines, or reacts, with other elements and compounds |
| corrosion | gradual wearing away of a metal due to chemical reaction |
| alkali metals | elements in group 1; most reactive metals |
| alkaline earth metals | elements in group 2; highly reactive metals |
| transition metals | elements in groups 3 - 12; includes many common metals |
| particle accelerator | machine that moves nuclei at higher and higher speeds so they collide and form heavier elements |
| nonmetal | an element that lacks most of the properties of a metal and tends to gain or share valence electrons in a chemical reaction |
| diatomic molecule | two identical nonmetal atoms chemically combined |
| halogens | element in group 17; most reactive nonmetals |
| noble gas | element in group 18; does not react or form compounds |
| metalloids | elements that have some characteristics of both metals and nonmetals; are all solids at room temperature |
| semiconductors | metalloids that can conduct electricity under some conditions but not under other conditions; used to make computer chips, transistors and lasers |
| protons | positively charged subatomic particles; found in the nucleus |
| valence electrons | electrons in outer energy level; are those involved in chemical reactions |
