1. CHEM 1405: Introductory Chemistry Houston Community College Dr. Laura Jakubowski Chapter 5 – The Periodic Table Textbook “Introductory Chemistry: Concepts and Critical Thinking” Seventh Edition by Charles H. Corwin © 2014 Pearson Education, Inc.

2. Classification of Elements By 1870, more than 60 elements had been discovered Dmitri Mendeleev proposed that properties of different elements (such as formula of oxide) repeat at regular intervals when they are arranged in order of increasing mass 2 © 2014 Pearson Education, Inc.

3. The Nobel Gases By the early 1900s, the group of elemental gases on the far right of the periodic table had been discovered They were originally called the inert gases, because they showed no chemical reactivity Since that time, reactions to form compounds with both xenon and krypton have been discovered – therefore the term for these gases was changed to the noble gases Similarly, the group of copper, silver, and gold are referred to as noble metals, because of their resistance to chemical reaction 3 © 2014 Pearson Education, Inc.

4. The Periodic Law Concept In 1913, H. G. J. Moseley discovered that nuclear charge (number of protons) increased by 1 for each element in the periodic table This led to the periodic law – which states that properties of elements recur in a repeating pattern when arranged in order of increasing atomic number and not increasing atomic mass 4 © 2014 Pearson Education, Inc. Element pairs circled in red are in order of increasing atomic number, but have a decrease in atomic mass

5. Groups and Periods of Elements A vertical column in the periodic table is called a group (18 groups) A horizontal row in the periodic table is called a period (7 periods) 5 © 2014 Pearson Education, Inc. alkali metals alkali earth metals halogens noble gases

6. Representative Elements and Transition Elements Groups of elements are also classified as either representative elements, transition elements, or inner transition elements 6 © 2014 Pearson Education, Inc. lanthanide series (rare earth elements are Ce-U) actinide series (transuranium elements) hydrogen’s properties are unlike any one group IUPAC (1-18) American (IA-VIIIA)

7. Periodic Trends Visualize atoms as spheres, where the atomic radius is the distance from the nucleus to the outermost electrons, atomic radius is expressed in nanometers (nm) Two trends atomic radius decreases up a group (number of energy levels decreases) atomic radius decreases across a period, left to right (nuclear charge pulls electrons closer to the nucleus) 7 © 2014 Pearson Education, Inc.

8. Periodic Trends Metallic character changes in a similar way Which has smaller radius? Na or K P or N Ca or Ni Si or S Which is most metallic? Sn or Pb Ag or Sr Al or B Br or As 8 © 2014 Pearson Education, Inc.

9. Periodic Trends Metallic character changes in a similar way Which has smaller radius? Na or K P or N Ca or Ni Si or S Which is most metallic? Sn or Pb Ag or Sr Al or B Br or As 9 © 2014 Pearson Education, Inc.

10. Properties of Elements It is possible to predict physical properties of elements based on trends shown by other elements in the same group Properties of Francium (Fr) can be predicted: atomic radius >0.266 nm, density >1.87 g/mL, melting point >28.4 °C, atomic mass >132.91 amu 10 © 2014 Pearson Education, Inc. Fr is just below Cs on the periodic table

11. Predicting Physical Properties Predict the missing value for each physical property listed below 11 © 2014 Pearson Education, Inc. Ca 0.197 1.54 (?) Sr 0.215 (?) 769 Ba (?) 3.65 725 Ni 0.125 8.91 (?) Pd 0.138 (?) 1554 Pt (?) 21.5 1772

12. Predicting Physical Properties Predict the missing value for each physical property listed below 12 © 2014 Pearson Education, Inc. Ca 0.197 1.54 (?) Sr 0.215 (?) 769 Ba (?) 3.65 725 Ni 0.125 8.91 (?) Pd 0.138 (?) 1554 Pt (?) 21.5 1772 0.233 (0.217) 2.60 (2.63) 813 (839) 0.151 (0.139) 15.2 (12.0) 1336 (1455)

13. Exceptions – “The Melting Spoon” Al: melting point is 660 °C, In: melting point is 157 °C, what about Ga? 13 See video at this link: http://www.youtube.com/watch?v=cvRcUeWjBu0 The melting point of Ga is very low: 30 °C

14. Predicting Chemical Properties Elements in the same group have similar chemical properties For example, Mg and O react to give MgO – Ca, Sr, and Ba should react similarly and they do, to give CaO, SrO, BaO, respectively Sodium + Chlorine  NaCl, predict the following: Lithium + Chlorine  ?? Potassium + Chlorine  ?? Given formulas for oxides CaO, Ga 2 O 3, K 2 O, GeO 2, predict the formula: rubidium oxide, ?? strontium oxide, ?? indium oxide, ?? lead oxide, ?? 14 © 2014 Pearson Education, Inc.

15. Predicting Chemical Properties Elements in the same group have similar chemical properties For example, Mg and O react to give MgO – Ca, Sr, and Ba should react similarly and they do, to give CaO, SrO, BaO, respectively Sodium + Chlorine  NaCl, predict the following: Lithium + Chlorine  Potassium + Chlorine  Given formulas for oxides CaO, Ga 2 O 3, K 2 O, GeO 2, predict the formula: rubidium oxide, strontium oxide, indium oxide, lead oxide, 15 © 2014 Pearson Education, Inc. LiCl KCl SrO PbO 2 In 2 O 3 Rb 2 O

16. Blocks of Elements Energy sublevels: 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p Periodic table is arranged by which sublevel is filled 16 © 2014 Pearson Education, Inc.

17. Electron Configuration of Elements Electron configurations of elements can be abbreviated by indicating the innermost electrons with the symbol of the preceding noble gas, and the outermost electrons with knowledge of blocks of elements For example, electron configuration for Na is 1s 2 2s 2 2p 6 3s 1 and for Ne is 1s 2 2s 2 2p 6 The abbreviation is written as: [Ne] 3s 1 Write the full and abbreviated electron configurations for each: P Co Zn Se 17 © 2014 Pearson Education, Inc.

18. Electron Configuration of Elements Electron configurations of elements can be abbreviated by indicating the innermost electrons with the symbol of the preceding noble gas, and the outermost electrons with knowledge of blocks of elements For example, electron configuration for Na is 1s 2 2s 2 2p 6 3s 1 and for Ne is 1s 2 2s 2 2p 6 The abbreviation is written as: [Ne] 3s 1 Write the full and abbreviated electron configurations for each: P – 1s 2 2s 2 2p 6 3s 2 3p 3, or [Ne] 3s 2 3p 3 Co – 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 7, or [Ar] 4s 2 3d 7 Zn – 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10, or [Ar] 4s 2 3d 10 Se – 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 4, or [Ar] 4s 2 3d 10 4p 4 18 © 2014 Pearson Education, Inc.

19. Valence Electrons When an atom undergoes a chemical change (reaction), only the outermost electrons are involved, known as valence electrons Ignoring transition elements, valence electrons are what occupy the outermost s and p orbitals Number of valence electrons is predicted using the group number Predict the number of valence electrons for: Na Al S Xe C 19 © 2014 Pearson Education, Inc.

20. Valence Electrons When an atom undergoes a chemical change (reaction), only the outermost electrons are involved, known as valence electrons Ignoring transition elements, valence electrons are what occupy the outermost s and p orbitals Number of valence electrons is predicted using the group number Predict the number of valence electrons for: Na – 1 Al – 3 S – 6 Xe – 8 C – 4 20 © 2014 Pearson Education, Inc.

21. Electron Dot Formulas An electron dot formula (also referred to as a Lewis structure) shows the symbol of an element surrounded by its valence electrons The symbol of the element represents the core electrons in an atom Dots are placed around the symbol to represent the valence electrons To draw an electron dot formula: Write the symbol of the element Draw a maximum of two dots on each side of symbol, (total maximum 8 e - : s + p = 2 e - + 6 e - = 8 e - ) Determine number of valence e - from periodic group, draw one dot per e - 21 © 2014 Pearson Education, Inc.

22. Draw the electron dot formulas for each of the following elements Si Xe K Br N Mg Al S Electron Dot Formulas 22 © 2014 Pearson Education, Inc.

23. Draw the electron dot formulas for each of the following elements Si Xe K Br N Mg Al S Electron Dot Formulas 23 © 2014 Pearson Education, Inc. Si Xe K Br N Mg Al S

24. Ionization Energy It is possible to for all elements to lose electrons, but metals lose electrons more easily than nonmetals Electrons are negatively charged, so metals become positively charged after losing an electron – any atom bearing a charge is called an ion The amount of energy required to remove an electron from a neutral atom (in the gaseous state) is called the ionization energy Na Na + + e - There are general trends in the periodic table regarding ionization energy – it increases up a group of elements and increases from left to right across a period of elements 24 © 2014 Pearson Education, Inc. ionization energy

25. Ionization energy Which has the higher ionization energy? Li or Na O or F Na or Mg O or S 25 © 2014 Pearson Education, Inc.

26. Ionization energy Which has the higher ionization energy? Li or Na O or F Na or Mg O or S 26 © 2014 Pearson Education, Inc.

27. Reactions of Alkali Metals with Water 27 Alkali metals react vigorously with water The order of their reactivity is related to each element’s ionization energy See video at this link: http://www.youtube.com/watch?v=eaChisV5uR0

28. Ionic Charges Generally, metals tend to lose electrons from their valence shell and nonmetals tend to add electrons to their valence shell – metals become positive and nonmetals become negative, they acquire an ionic charge The typical ionic charge of an element is related to its number of valence electrons Predict ionic charge: Al S Mg Br P 28 © 2014 Pearson Education, Inc.

29. Ionic Charges Generally, metals tend to lose electrons from their valence shell and nonmetals tend to add electrons to their valence shell – metals become positive and nonmetals become negative, they acquire an ionic charge The typical ionic charge of an element is related to its number of valence electrons Predict ionic charge: 29 © 2014 Pearson Education, Inc. Al 3+ S 2- Br - P 3- Mg 2+

30. Isoelectronic Ions A sodium ion (Na + ) and a fluoride ion (F - ) and neutral neon (Ne) each have 10 electrons – but their properties are very different Two or more ions having the same number of electrons are said to be isoelectronic For example, which of the following are isoelectronic with Ar? K +, Br -, Ca 2+, or O 2- Both K + and Ca 2+ have 18 electrons, the same as Ar Find the noble gas which is isoelectronic with the following: Cs + Xe Cl - Ar La 3+ Xe Se 2- Kr 30 © 2014 Pearson Education, Inc.

31. Isoelectronic Ions A sodium ion (Na + ) and a fluoride ion (F - ) and neutral neon (Ne) each have 10 electrons – but their properties are very different Two or more ions having the same number of electrons are said to be isoelectronic For example, which of the following are isoelectronic with Ar? K +, Br -, Ca 2+, or O 2- Both K + and Ca 2+ have 18 electrons, the same as Ar Find the noble gas which is isoelectronic with the following: Cs + Xe Cl - Ar La 3+ Xe Se 2- Kr 31 © 2014 Pearson Education, Inc.

32. Electron Configuration of Ions To write the electron configuration for a positive ion, remove the number of electrons that corresponds to the positive charge For example Note – transition metals lose two electrons from the highest s sublevel first before losing electrons from their outer d subevel For example Electron configurations can be simplified using a noble gas symbol to represent core electrons – this method is called core notation 32 © 2014 Pearson Education, Inc. Na atom loses 1 e - Na + ion 1s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 Mn atom loses 2 e - Mn 2+ ion 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5

33. Electron Configuration of Ions To write the electron configuration for a negative ion, add the number of electrons that corresponds to the negative charge For example (using core notation) Write the electron configuration for each of the following ions: Fe 3+ Se 2- Cd 2+ P 3- Mg 2+ F - 33 © 2014 Pearson Education, Inc. Cl atom gains 1 e - Cl - ion [Ne] 3s 2 3p 5 [Ne] 3s 2 3p 6

34. Electron Configuration of Ions To write the electron configuration for a negative ion, add the number of electrons that corresponds to the negative charge For example (using core notation) Write the electron configuration for each of the following ions: Fe 3+ [Ar] 3d 5 Se 2- [Kr] Cd 2+ [Kr] 4d 10 P 3- [Ar] Mg 2+ [Ne] F - [Ne] 34 © 2014 Pearson Education, Inc. Cl atom gains 1 e - Cl - ion [Ne] 3s 2 3p 5 [Ne] 3s 2 3p 6

35. Where Did the Elements Come From? It is estimated that the universe is 14 billion years old and began with an event known as the “Big Bang” During this time, there is evidence for both hydrogen and helium atoms being formed – what about heavier elements? Two hydrogen atoms combine to form a helium atom – a process known as nuclear fusion It is speculated that heavier nuclei formed similarly Through a process called nucleosynthesis, it may be possible that H and He can form Li, which in turn forms Be and eventually C, and so on... 35 © 2014 Pearson Education, Inc.

36. Summary 36 © 2014 Pearson Education, Inc. Mendeleev published a periodic table in 1871, which arranged elements by increasing atomic mass and grouped them by property In 1913, this table was revised to order elements by atomic number – periodic law was rewritten to state that physical and chemical properties repeat periodically when elements are arranged in this way The periodic table is organized into groups and periods. Certain groups have family names: alkali metals, alkaline earth metals, halogens, and noble gases. Groups 1, 2, and 13-18 are referred to as representative elements. Groups 3-12 are transition elements. Elements Ce-Lu are lanthanides, elements Th-Lr are actinides. Elements Sc, Y, La and Ce-Lu are rare earth metals, and elements beyond U are transuranium elements

37. Summary 37 © 2014 Pearson Education, Inc. Atomic radius decreases up a group and from left to right, metallic character also decreases up and group and from left to right Trends in the periodic table allow us to predict properties The periodic table is arranged by outermost sublevels, this is useful to write out electron configuration in a faster way The outermost electrons in the s and p sublevels are known as valence electrons, which also corresponds to group number The electron dot formula uses the chemical symbol to represent core electrons and dots to represent valence electrons When an element gains or loses electron(s), the resulting positively or negatively charged atom is called an ion

38. Summary 38 © 2014 Pearson Education, Inc. The amount of energy required to remove an electron from an atom is called the ionization energy – increases up a group and from left to right Ionic charge can be predicted from group number, ions with equivalent number of electrons are isoelectronic, electron configuration for an ion is written by adding or subtracting electrons corresponding to the ionic charge Key terms: periodic law, group, period, representative elements, transition elements, alkali metals, alkaline earth metals, halogens, noble gases, lanthanides, actinides, inner transition elements, rare earth elements, transuranium elements, electron configuration, valence electrons, core electrons, electron dot formula, ions, ionization energy, ionic charge, isoelectronic, core notation