2. Elements, Atoms, and Ions Chapter 4

3. The Language of Chemistry CHEMICAL ELEMENTS -CHEMICAL ELEMENTS - –pure substances that cannot be decomposed by ordinary means to other substances. Sodium Bromine Aluminum

4. The Language of Chemistry The elements, their names, and symbols are given on the PERIODIC TABLEThe elements, their names, and symbols are given on the PERIODIC TABLE Periods (rows) give you the # of energy levels an atom hasPeriods (rows) give you the # of energy levels an atom has Families/Groups (columns) give you the # of electrons in the outer energy level (ValenceFamilies/Groups (columns) give you the # of electrons in the outer energy level (Valence

5. The Periodic Table Dmitri Mendeleev (1834 - 1907)

6. An atom consists of a nucleusnucleus –(of protons and neutrons) electrons in space about the nucleus.electrons in space about the nucleus. The Atom Nucleus Electron cloud

7. Copper atoms on silica surface. An _____ is the smallest particle of an element that has the chemical properties of the element.An _____ is the smallest particle of an element that has the chemical properties of the element. Distance across = 1.8 nanometer (1.8 x 10 -9 m)

8. Compounds Compounds are also pure substances. But compounds are made from more than one element. Water is a compound. Water can be broken down into simpler substances – hydrogen and oxygen.

9. Compounds –composed of 2 or more elements in a fixed ratio –properties differ from those of individual elements –EX: table salt (NaCl)

10. A MOLECULE is the smallest unit of a compound that retains the chemical characteristics of the compound. Composition of molecules is given by a MOLECULAR or CHEMICAL FORMULA H2OH2OH2OH2O C 8 H 10 N 4 O 2 - caffeine

11. Chemical formula tells you a lot of information: H2OH2OH2OH2O C 8 H 10 N 4 O 2 - caffeine The letter or SYMBOLS tell the types of elements in the formula

12. Chemical formula tells you a lot of information: H2OH2OH2OH2O C 8 H 10 N 4 O 2 - caffeine The numbers following the symbols tell how many atoms there are of that element

13. Regions of the Periodic Table metals metalloids Non-metals Most reactiveleast reactive Requires very little Energy to loose electrons Requires large amounts of Energy to loose electrons

14. Combing atoms - 2 ways Ionic bonds - the atoms overall charge is changed by giving up or taking on an electron. it becomes more positive or more negative Covalent bonds - the atoms share electrons with each other to form a molecule which is overall neutral.

15. Ions IONS are atoms or groups of atoms with a positive or negative charge.IONS are atoms or groups of atoms with a positive or negative charge. Taking away an electron from an atom gives a CATION with a positive chargeTaking away an electron from an atom gives a CATION with a positive charge Adding an electron to an atom gives an ANION with a negative charge.Adding an electron to an atom gives an ANION with a negative charge. To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na + Ca +2 I - O -2To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na + Ca +2 I - O -2 Na Ca I O Na Ca I O

16. Forming Cations & Anions A CATION forms when an atom loses one or more electrons. An ANION forms when an atom gains one or more electrons Mg --> Mg 2+ + 2 e- F + e- --> F -

17. PREDICTING ION CHARGES In general metals (Mg) lose electrons ---> cationsmetals (Mg) lose electrons ---> cations nonmetals (F) gain electrons ---> anionsnonmetals (F) gain electrons ---> anions

18. Charges on Common Ions -2-3 +1 +2 By losing or gaining e-, atom has same number of e-’s as nearest Group 8A atom.

19. The Periodic Table

20. Periods in the Periodic Table

21. Groups in the Periodic Table Elements in groups react in similar ways!

22. Group 1A: Alkali Metals Cutting sodium metal Reaction of potassium + H 2 O

23. Magnesium Magnesium oxide Group 2A: Alkaline Earth Metals

24. Group 7A: The Halogens (salt makers) F, Cl, Br, I, At

25. Group 8A: The Noble (Inert) Gases He, Ne, Ar, Kr, Xe, Rn Lighter than air balloons “Neon” signs Very Unreactive because they have full electron levels XeOF 4

26. Transition Elements Lanthanides and actinides Iron in air gives iron(III) oxide

27. ELEMENTS THAT EXIST AS DIATOMIC MOLECULES Remember: BrINClHOF These elements only exist as PAIRS. Note that when they combine to make compounds, they are no longer elements so they are no longer in pairs!