1. Dimitri Mendeleev- The father of the modern periodic table. Russian chemist who in the late 1800’s arranged elements by increasing atomic mass. He discovered a pattern of repeating properties found in lighter elements repeated in heavier elements.

2. Periodic Table- a table of elements arranged according to repeated changes in properties.

3. Periodic Law- a recurring pattern in the properties of the elements when they are arranged in order of increasing atomic number, the total number of protons in the nucleus. The periods (horizontal rows) of the periodic table illustrate these relationships. nucleus periodic table

4. Families/Groups- In the periodic table, each of the 18 vertical columns of elements, each is made up of elements with similar properties.

5. Atomic #- the number of protons in an atom

6. Chuck Norris destroyed the periodic table, because he only recognizes the element of surprise.

7. Periods A horizontal row on the periodic table

8. Atomic mass/Weight The average mass of one atom of an element

9. Mass Number Sum of the protons and neutrons in an atom’s nucleus

10. Valence Electrons Electrons in the outermost energy level of an atom; in large part, they determine an elements chemical properties.

11. Isotopes Atoms of the same element that have different numbers of neutrons; for example boron- 10 and boron-11.

12. Ion A positively or negatively charged atom. Shown as a subscript (written above) adjacent to the elements symbol.

13. Metal Elements that usually have these properties: shiny, good conductors of heat and electricity, are solids at room temperature. On the periodic table they are found to the left of the stair-step line.

14. Non-metal Elements that are gases or brittle solids at room temperature, most do not conduct heat or electricity well. On the periodic table they are found to the right of the stair-step line.

15. Metalloid Have the properties of both metals and non-metals. In the periodic table they are found along the line that seperates metals and non-metals.

16. Transition Metals Elements in groups 3-12 on the periodic table, these are typically metals with one or two electrons in their other level.

17. Alkali Metals An alkali metal is any of the elements found in Group I of the periodic table. Alkali metals are very reactive chemical species which readily lose their one valence electron to form ionic compounds with nonmetals.

18. Alkaline-Earth Metals Any of the six chemical elements in the second leftmost group of the periodic table (beryllium, magnesium, calcium, strontium, barium, and radium). Their atoms have two electrons in the outermost shell, so they react readily, form numerous compounds, and are never found free in nature.berylliummagnesiumcalciumstrontium bariumradium

19. Noble Gases Any of the elements in the far right group (group 8) of the periodic table, including helium, neon, argon, krypton, xenon, and radon, which are monatomic and with limited exceptions chemically inert and do not bond with elements because their valence shell is full.

20. Lanthanides any element of the lanthanide series (atomic numbers 57 through 71)rare-earth elements. They are grouped apart from the rest of the elements in the Periodic Table because they all behave in a similar way in chemical reactions.

21. Actinides Any of the series of 15 consecutive chemical elements in the periodic tablefrom actinium to lawrencium (atomic numbers 89–103). All are radioactive heavy metals; and only the first four (actinium, thorium, protactinium, and uranium) occur in nature. The other 11 (the transuranium elements) are unstable and are produced only artificially.