Atoms, Elements & the Periodic Table

1. Atoms, Elements & the Periodic Table

2. Pre-Periodic Table Chemistry… • was a mess! • No organization of elements. • Imagine going to a grocery store with no organization. • Difficult to find information. • Chemistry didn’t make sense.

3. I am Dmitri Mendeleev! I made the PERIODIC TABLE !

4. Dmitri Mendeleev:Father of the Table FUN FACTS • He left blank spaces for what he said were undiscovered elements. (Turned out he was right!) • He broke the pattern of increasing atomic weight to keep similar reacting elements together. HOW HIS WORKED… • Put elements in rows by increasing atomic weight. • Put elements in columns by the way they reacted.

5. Families or Groups Periods

6. Groups or families…Here’s Where the Periodic Table Gets Useful! • Elements in the same group or family have similar chemical and physical properties! • (Mendeleev did that on purpose.)

7. Families on the Periodic Table • Columns are families or groups. • Families are typically one column. • Families all have names. (Just like your family has a common last name.)

8. Hydrogen • Hydrogen belongs to a family of its own. • Hydrogen is a highly reactive gas. • Hydrogen was involved in the explosion of the Hindenberg.

9. Alkali Metals • 1st column on the periodic table (not including hydrogen) • Very reactive metals, always combined with something else in nature (like in salt). • Soft enough to cut with a butter knife

10. Alkaline Earth Metals • Second column on the periodic table. • Reactive metals that are always combined with nonmetals in nature. • Several of these elements are important mineral nutrients (such as Mg and Ca)

11. Transition Metals • Elements in the center columns of the table • Less reactive harder metals • Includes metals used in jewelry and construction.

12. Halogens • Elements in second to last family • Very reactive nonmetals • Always found combined with other element(s) in nature • Used as disinfectants and to strengthen teeth

13. The Noble Gases • Elements in last family • VERY unreactive gases • Used in lighted “neon” signs

14. What’s in an atom of a given element? • An atom has three parts: • Proton = positive (+) charge • Neutron = no charge • Electron = negative (-) charge

15. Opposites Attract • Positive charges, such as protons, are attracted to negative charges, such as electrons (opposites attract) • Like charges repel (positive charges repel other positive charges, and negative charges repel other negative charges)

16. What’s in an atom? • The protons & neutrons are found in the center of the atom in the nucleus. • The electrons orbit the nucleus.

17. What is the ATOMIC NUMBER? • The number of protons found in the nucleus of an atom or • The number of electrons surrounding the nucleus of a neutral atom.

18. What is the ATOMIC NUMBER? The atomic number is unique to that element. No two elements have the same atomic number.

19. Key to the Periodic Table • Elements are organized on the table according to their atomic number, usually found near the top of the square.

20. What is the MASS NUMBER? • The number of protons and neutrons in the nucleus of an atom. • THIS IS NOT ON THE PERIODIC TABLE! MASS NUMBER IS NOT ATOMIC MASS/WEIGHT!

21. For all neutral atoms… • # of PROTONS= ATOMIC # • # of ELECTRONS = ATOMIC # • # of NEUTRONS = MASS # – ATOMIC #