1. Chapter 6 The Periodic Table 6.3 Periodic Trends
6.1 Organizing the Elements
6.2 Classifying the Elements
6.3 Periodic Trends
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

2. CHEMISTRY & YOU
How are trends in the weather similar to trends in the properties of elements?
Although the weather changes from day to day, the weather you experience is related to your location on the globe.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

3. Trends in Atomic Size
Trends in Atomic Size
What are the trends among the elements for atomic size?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

4. Trends in Atomic Size
In general, atomic size increases from top to bottom within a group, and decreases from left to right across a period.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

5. Trends in Atomic Size
One way to think about atomic size is to look at molecules , the units that form when atoms of the same element are joined to one another.
Because the atoms in each molecule are identical, the distance between the nuclei (center) of these atoms can be used to estimate the size of the atoms.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

6. This size is expressed as an atomic radius.
Trends in Atomic Size
This size is expressed as an atomic radius.
The atomic radius is one-half of the distance between the nuclei of two atoms of the same element when the atoms are joined.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

7. Trends in Atomic Size
The distances between atoms in a molecule are extremely small so the atomic radius is measured in picometers (pm).
There are one trillion, or 1012, picometers in a meter.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

8. Distance between the nuclei
Trends in Atomic Size
The distance between the nuclei in an iodine molecule is 280 pm.
Distance between the nuclei
280 pm
140 pm
Atomic radius
Atomic radius is one-half the distance between the nuclei, a value of 140 pm (280/2) is assigned to the radius of the iodine atom.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

9. Group Trends in Atomic Size
As the atomic number increases within a group 2 things occur.
1.) the charge on the nucleus increases
2.) number of occupied energy levels increases.
These variables affect atomic size in opposite ways.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

10. Group Trends in Atomic Size
1.) The increase in positive charge draws electrons closer to the nucleus. (smaller)
2.) The increase in the number of occupied orbitals shields electrons in the highest occupied energy level from the attraction of protons in the nucleus. (larger)
The shielding effect is greater than the effect of the increase in nuclear charge.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

11. Group Trends in Atomic Size
Interpret Graphs
Group Trends in Atomic Size
The atomic radius within a group increases as the atomic number increases.
Atomic radius (pm)
Atomic number
This increase is an example of a trend.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

12. Periodic Trends in Atomic Size
Across a period, the electrons are added to the same principal energy level.
The shielding effect is constant for all elements in a period.
The increasing nuclear charge pulls the electrons in the highest occupied energy level closer to the nucleus, and the atomic size decreases.
Atomic radius (pm)
Atomic number
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

13. Trends in Atomic Size
The figure below summarizes the group and period trends in atomic size.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

14. What are the trends for atomic size?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

15. What are the trends for atomic size?
In general, atomic size increases from top to bottom within a group and decreases from left to right across a period.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

16. Ions
An atom is electronically neutral because it has equal numbers of protons and electrons.
An atom of sodium (Na) has 11 positively charged protons and 11 negatively charged electrons.
The net charge on a sodium atom is zero. (+11) + (-11) = 0
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

17. Ions How do ions form? Ions
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

18. Ions
Positive and negative ions form when electrons are transferred between atoms.
Metals tend to form ions by losing one or more electrons from their highest occupied energy levels.
Non-metals tend to form ions by gaining one or more electrons in their highest occupied energy levels.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

19. An ion with a positive charge is called a cation.
Ions
An ion is an atom or group of atoms that has a positive or negative charge.
An ion with a positive charge is called a cation.
The charge for a cation is written as a superscript with a number followed by a plus sign.
If the charge is 1+, the number in 1 is usually omitted from the symbol for the ion.
For example, Li1+ is written as Li+.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

20. An ion with a negative charge is called an anion.
Ions
An ion is an atom or group of atoms that has a positive or negative charge.
An ion with a negative charge is called an anion.
The charge for an anion is written as a superscript with a number followed by a minus sign.
If the charge is 1-, the number in 1 is usually omitted from the symbol for the ion.
For example, Br1- is written as Br -.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

21. Ions
In the sodium ion, the number of electrons (10) is not equal to the number of protons (11).
there are more positively charged protons than negatively charged electrons; the ion has a net positive charge.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

22. Ions
In a chloride ion, the number of electrons (18) is not equal to the number of protons (17).
there are more negatively charged electrons than positively charged protons, the ion has a net negative charge.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

23. What type of element tends to form anions
What type of element tends to form anions? What type tends to form cations?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

24. Nonmetals tend to form anions. Metals tend to form cations.
What type of element tends to form anions? What type tends to form cations?
Nonmetals tend to form anions. Metals tend to form cations.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

25. Trends in Ionization Energy
Sometimes an electron has enough energy to overcome the attraction of the protons in the nucleus and escape the atom.
The energy required to remove an electron from an atom is called ionization energy.
This energy is measured when an element is in its gaseous state.
The energy required to remove the first electron from an atom is called the first ionization energy.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

26. Trends in Ionization Energy
What are the trends among the elements for first ionization energy?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

27. Trends in Ionization Energy
First ionization energy tends to decrease from top to bottom within a group and increase from left to right across a period.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

28. Ionization Energies of Some Common Elements
Interpret Data
Ionization Energies of Some Common Elements
Symbol
First
Second
Third H
1312
He (noble gas)
2372
5247 Li
520
7297
11,810 Be
899
1757
14,840 C
1086
2352
4619 O
1314
3391
5301 F
1681
3375
6045
Ne (noble gas)
2080
3963
6276 Na
496
4565
6912 Mg
738
1450
7732 S
999
2260
3380
Ar (noble gas
1520
2665
3947 K
419
3096
4600 Ca
590
1146
4941
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

29. Trends in Ionization Energy
Ionization energies can help you predict what ions an element will form.
It is relatively easy to remove one electron from a Group 1 metal atom, but it is difficult to remove a second electron.
This difference indicates that Group 1 metals tend to form ions with a 1+ charge.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

30. Group Trends in Ionization Energy
Interpret Graphs
Group Trends in Ionization Energy
Look at the data for noble gases and alkali metals.
First ionization energy (kJ/mol)
Atomic number
In general, first ionization energy generally decreases from top to bottom within a group.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

31. Trends in Ionization Energy
Group Trends in Ionization Energy
As the size of the atom increases, the nuclear charge has a smaller effect on the electrons in the highest occupied energy level. (shielding)
Less energy is required to remove an electron from this energy level, and the first ionization energy is lower.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

32. Trends in Ionization Energy
Periodic Trends in Ionization Energy
The nuclear charge increases across the period, but the shielding effect remains constant.
As a result, there is an increase in the attraction of the nucleus for an electron.
Thus, it takes more energy to remove an electron from an atom.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

33. Trends in Ionization Energy
The figure below summarizes the group and period trends for the first ionization energy.
Ionization Energy generally increases (because the nucleus is stronger)
Ionization Energy generally decreases (because electrons are farther away from nucleus)
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

34. Trends in Ionic Size
Trends in Ionic Size
What are the trends among the elements for ionic size?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

35. Trends in Ionic Size
Ionic size tends to increase from top to bottom within a group. Generally, the size of cations and anions decreases from left to right across a period.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

36. Trends in Ionic Size
During reactions between metals and nonmetals, metal atoms tend to lose electrons and nonmetal atoms tend to gain electrons.
This transfer of electrons has a predictable effect on the size of the ions that form.
Cations are always smaller than the atoms from which they form.
Anions are always larger than the atoms from which they form.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

37. Group Trends in Ionic Size
For each of these elements, the ion is much smaller than the atom.
The radius of a sodium ion (95 pm) is about half the radius of a sodium atom (191 pm).
When a sodium atom loses an electron, the attraction between the remaining electrons and the nucleus is increased. As a result, the electrons are drawn closer to the nucleus.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

38. Group Trends in Ionic Size
The trend is the opposite for nonmetals, like the halogens in Group 17.
For each of these elements, the ion is much larger than the atom.
For example, the radius of a fluoride ion (133 pm) is more than twice the radius of a fluorine atom (62 pm).
As the number of electrons increases, the attraction of the nucleus for any one electron decreases.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

39. Group Trends in Ionic Size
Metals that are representative elements tend to lose all their outermost electrons during ionization.
Therefore, the ion has one fewer occupied energy level.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

40. Period Trends in Ionic Size
From left to right across a period, two trends are visible—a gradual
decrease in the
size of the positive
ions (cations),
followed by a
gradual decrease
in the size of the
negative ions
(anions).
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

41. The figure below summarizes the group and period trends in ionic size.
Size of cations decreases
Size of anions decreases
Size generally increases
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

42. What are the trends for ionic size?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

43. What are the trends for ionic size?
Ionic size tends to increase from top to bottom within a group. Generally, the size of cations and anions decreases from left to right across a period.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

44. Trends in Electronegativity
There is a property called electronegativity that can be used to predict the type of bond that will form during a reaction.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

45. Trends in Electronegativity
There is a property called electronegativity that can be used to predict the type of bond that will form during a reaction.
Electronegativity is the ability of an atom of an element to attract electrons when the atom is in a compound.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

46. Trends in Electronegativity
What are the trends among the elements for electronegativity?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

47. Trends in Electronegativity
In general, electronegativity values decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period.
Metals at the far left of the periodic table have low values.
By contrast, nonmetals at the far right (excluding noble gases) have high values.
Values among transition metals are not as regular.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

48. Electronegativity Values for Selected Elements
Interpret Data
This table lists electronegativity values for representative elements in Groups 1 through 17.
Electronegativity Values for Selected Elements H
2.1 Li
1.0 Be
1.5 B
2.0 C
2.5 N
3.0 O
3.5 F
4.0 Na
0.9 Mg
1.2 Al Si
1.8 P S Cl K
0.8 Ca Ga
1.6 Ge As Se
2.4 Br
2.8 Rb Sr In
1.7 Sn Sb
1.9 Te I Cs
0.7 Ba Tl Pb Bi
The data in this table is expressed in Pauling units.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

49. Trends in Electronegativity
The least electronegative elements in the table are cesium and francium, with an electronegativity of 0.7.
They have the least tendency to attract electrons.
When they reacts, they tends to lose electrons and form cations.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

50. Trends in Electronegativity
The most electronegative element is fluorine, with a value of 4.0.
Because fluorine has such a strong tendency to attract electrons, when it is bonded to any other element it either attracts the shared electrons or forms an anion.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

51. Trends in Electronegativity
This figure summarizes several trends that exist among the elements.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

52. What are the trends for electronegativity values?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

53. What are the trends for electronegativity values?
In general, electronegativity values decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

54. Key Concepts
In general, atomic size increases from top to bottom within a group and decreases from left to right across a period.
Positive and negative ions form when electrons are transferred between atoms.
First ionization energy tends to decrease from top to bottom within a group and decrease from left to right across a period.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

55. Key Concepts
Ionic size tends to increase from top to bottom within a group. Generally, the size of cations and anions decreases from left to right across a period.
In general, electronegativity values decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

56. END OF 6.3
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .