1. Lecture 2: Atoms and Elements
Lecture Outline
Defining matter and its types
Elements and symbols
The periodic table
The atom
Atomic number and mass number
Isotopes and atomic mass
Electron energy levels
Electron configuration
Periodic trends
(as in before, group activity takes center and front in the lecture)

2. Defining Matter and its types
Matter: Matter is stuff. it is what makes up a substance. Matter makes things we see everyday such as water, wood, cooking pan, clothes, shoes, etc.

3. Properties of Matter Type of Properties Physical Chemical
Obtained without changing identity
(No color, shape, taste, or density change)
Chemical
Obtained by changing identity
(New color, shape, taste, etc)
Chemical Change
Change in which new substances
are formed by changing identity
Physical Change
Change without changing identity
and no new substances formed

4. Elements and Symbols
Robert Boyle ( : Elements are substances that cannot be separated into simpler substances
Robert had no preconceived ideas about how many elements there might be …
Elements are the building blocks of matter
gold
carbon
aluminum
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

5. Number of Elements
Matter is composed of 115 different elements (88 naturally occurring)  millions of compounds
In comparison, English language has 26 letters  millions of words and sentences
Elements not evenly distributed
9 elements in the earth’s crust make up 98% of the mass
Oxygen is the most abundant: 20% of air, almost 50% of earth’s crust
Elements in living matter also not evenly distributed  selected for biological function
Oxygen is still most abundant, followed by carbon, hydrogen, and nitrogen
Calcium, phosphorus, magnesium, potassium, sodium, chlorine, sulfur, and iron are all present in significant amounts

6. Element Names Places of discovery Planets minerals People (Scientists)
Element named after many things:
Places of discovery
Planets
minerals
People (Scientists)
Colors
Mythology
LecturePLUS Timberlake

7. Learn the FIRST 20 elements and their names (TEST Material)
Symbols of Elements
Learn the FIRST 20 elements and their names (TEST Material)

8. Symbols from Latin Names
Some symbols are derived from Latin names as shown
below:
Cu, copper (cuprum) Au, gold (aurum)
Fe, iron (ferrum) Ag, silver (argentum)
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

9. The Periodic Table: Groups vs. Periods
Groups contain elements with similar properties in vertical columns.
Periods are horizontal rows of elements.
LecturePLUS Timberlake

10. The Periodic Table

11. Group Numbers Group Numbers
Use the letter A for the representative elements (1A to 8A) and the letter B for the transition elements
Also use numbers 1-18 to the columns from left to right
Several groups of representative elements have common names
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

12. Metals, Nonmetals, and Metalloids
The heavy zigzag line
separates metals and
nonmetals
Metals are located to the left
Nonmetals are located to the right.
Metalloids are located along the heavy zigzag line between the metals and nonmetals
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

13. Properties of Metals, Nonmetals, and Metalloids
Are shiny and ductile
Are good conductors of heat and electricity
Nonmetals
Are dull, brittle, and poor conductors of heat and electricity
Are good insulators
Metalloids
Are better conductors than nonmetals, but not as good as metals
Are used as semiconductors and insulators
NS: Table 2.5 shows more extensive comparison
GR: Table 3.5
LecturePLUS Timberlake

14. Pause: ALE 2
Group activity: all groups work on problems on ALE IIB worksheet, problems 3-6
Need volunteers to work on the problems written on the board. If no volunteers immediately, will call names. Everyone will do problems on the board sooner or later
While working on the problems, ask if you have any questions. I’m more than happy to help
LecturePLUS Timberlake

15. Dalton’s Atomic Theory
Atoms
Are tiny particles of matter
Of an element are similar and different from other elements
Of two or more different elements combine to form compounds
Are rearranged to form new combinations in a chemical reaction
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

16. Subatomic Particles Atoms contains subatomic particles.
Protons have a positive (+) charge.
Electrons have a negative (-) charge.
Neutrons are neutral
Coulomb's law: Like charges repel
and unlike charges attract
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

17. Structure of the Atom An atom consists
Of a nucleus that contains protons and neutrons
Of electrons in a large, empty space around the nucleus
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

18. Atomic Mass Scale On the atomic mass scale for subatomic particles
1 atom mass unit (amu) is defined as 1/12 of the mass of the carbon-12 atom
A proton has a mass of about 1 (1.007) amu
A neutron has a mass of about 1(1.008) amu
An electron has a very small mass, amu
LecturePLUS Timberlake

19. Atomic Number and Mass Number
The atomic number
Is specific for each element and is the same for all atoms of an element.
Is equal to the number of protons in an atom.
Appears above the symbol of an element.
The mass number : represents the number of particles in the nucleus and is equal to sum of protons and neutrons in the nucleus. Number of protons + Number of neutrons 11 Na
Atomic Number
Symbol
LecturePLUS Timberlake

20. Atomic Number and Protons
Examples of atomic number and number of protons:
Hydrogen has atomic number 1, every H atom has one proton.
Carbon has atomic number 6, every C atom has six protons.
Copper has atomic number 29, every Cu atom has 29 protons.
Gold has atomic number 79, every Au atom has 79 protons.

21. Number of Electrons in Atom
Atoms are neutral
In each atom, number of protons is equal to that of electrons
number of protons = number of electrons
For instance, an aluminum atom has 13 protons and 13 electrons. The net charge is zero
13 protons (13+) electrons (13 -) = 0

22. Isotopes and Isotopic Notation
Elements of same type, same number of protons, but different number of neutrons.
Isotopes have identical properties, mass, and sometimes radioactivity
Nuclear Symbol
Example: Sodium atom

23. Nuclear Symbols For an atom, the nuclear symbol gives the number of
Protons (p+)
Neutrons (n)
Electrons (e-)
O P Zn
8 p+ 15 p p+
8 n 16 n 35 n
8 e- 15 e e-

24. Atomic Mass Na 22.99 Summary The atomic mass of an element
Is listed below the symbol of each element on the periodic table.
Gives the mass of an “average” atom of each element compared to 12C.
Is not the same as the mass number Na
22.99
Summary
Atomic mass = average mass of an atom in each element
Mass number = # of protons + # of neutrons in the nucleus
Atomic number = number of protons in an atom

25. Learning Check Fill the following table for neutral atoms: Boron 10 Cl
Element Name
Symbol
Atomic Number
Mass Number
Number of Protons
Number of Neutrons
Number of Electrons
Boron 10 Cl 35 8 16 92
146 6

26. Elements and Their Atomic Mass
Most elements have two or more isotopes that contribute to the atomic mass of that element.

27. Calculating Average of Masses
To calculate an atomic mass, the contribution of each isotope is determined by multiplying the mass of each isotope by its percent abundance and adding the results
Example: magnesium has three isotopes, Mg-24 (23.99 amu, 78.70%), Mg-25 (24.99 amu, 10.13%) and Mg-26 (25.98 amu, 11.17%). Calculate the atomic mass of magnesium.
Isotope:
Mass x
Abundance (%) =
Contribution to average Mg amu
24Mg
25Mg
26Mg
23.99
24.99
25.98
78.70/100
10.13/100
11.17/100
Average Atomic Mass:
18.88
2.532
2.902
24.31
LecturePLUS Timberlake

28. Pause: ALE 2
Group activity: all groups work on problems on ALE 2 worksheet, problems 1and 2, 7-9
While working on the problems, ask if you have any questions. I’m more than happy to help
LecturePLUS Timberlake

29. Lecture 2: Atoms and Elements
Electron Energy Levels
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

30. Electron Energy Levels
Electrons are arranged in
specific energy levels that
Are labeled n = 1, n = 2, n = 3, and so on.
Increase in energy as n increases.
Have the electrons with the lowest energy in the first energy level (n=1)closest to the nucleus.
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

31. Energy Level Changes
An electron absorbs energy to “jump” to a higher energy level.
When an electron falls to a lower energy level, energy is emitted.
In the visible range, the emitted energy appears as a color.
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

32. Energy Emitted LecturePLUS Timberlake
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

33. Sublevels Sublevels Contain electrons with the same energy.
Are found within each energy level.
Are designated by the letters s, p, d, f.
The number of sublevels is equal to the value of the principal quantum number (n).
LecturePLUS Timberlake

34. Number of Sublevels LecturePLUS Timberlake
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

35. Energy of Sublevels In any energy level,
The s sublevel has the lowest energy.
The s sublevel is followed by the p, d, and f sublevels in order of increasing energy.
Higher sublevels are possible, but only s, p, d, and f sublevels are needed to hold the electrons in the atoms known today.
LecturePLUS Timberlake

36. Orbitals
An orbital
Is a three- dimensional space around a nucleus where an electron is most likely to be found.
Has a shape that represents electron density (not a path the electron follows).
Can hold up to 2 electrons.
Contains two electrons that must spin in opposite directions.
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

37. s Orbitals An s orbital Has a spherical shape around the nucleus.
Increases in size around the nucleus as the energy level n value increases.
Is a single orbital found in each s sublevel.
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

38. p Orbitals A p orbital Has a two-lobed shape.
Is one of three p orbitals that make up each p sublevel.
Increases in size as the value of n increases.
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

39. Sublevels and Orbitals
Each sublevel consists of a specific number of
orbitals.
An s sublevel contains one s orbital.
A p sublevel contains three p orbitals.
A d sublevel contains five d orbitals.
An f sublevel contains seven f orbitals.
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

40. Electrons in Each Sublevel
Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
LecturePLUS Timberlake

41. Pause: ALE 2
Group activity: all groups work on problems on ALE 2 worksheet, problems 11 and 12
Need volunteers to work on the problems written on the board. If no volunteers immediately, will call names. Everyone will do problems on the board sooner or later
While working on the problems, ask if you have any questions. I’m more than happy to help
LecturePLUS Timberlake

42. Lecture 2: Atoms and Elements
Electron Configurations
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

43. Order of Filling Energy levels are filled with electrons
In order of increasing energy.
Beginning with quantum number n = 1.
Beginning with s followed by p, d, and f.
LecturePLUS Timberlake

44. Energy Diagram for Sublevels
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

45. Orbital Diagrams An orbital diagram shows
Orbitals as boxes in each sublevel.
Electrons in orbitals as vertical arrows.
Electrons in the same orbital with opposite spins (up and down vertical arrows).
Orbital diagram for Li
1s s p
filled half-filled empty
LecturePLUS Timberlake

46. Order of Filling Electrons in an atom
Fill orbitals in sublevels of the same type with one electron until half full,
Then pair up in the orbitals using opposite spins.
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

47. Writing Orbital Diagrams
The orbital diagram
for carbon consists of
Two electrons in the 1s orbital.
Two electrons in the 2s orbital.
One electron each in two of the 2p orbitals
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

48. Individual Learning Check
Write the orbital diagrams for
A. Nitrogen
B. oxygen
C. magnesium
LecturePLUS Timberlake

49. Electron Configuration
An electron configuration
Lists the sublevels filling with electrons in order of increasing energy.
Uses superscripts to show the number of electrons in each sublevel.
For neon (10 electrons) is as follows:
number of electrons
sublevel s2 2s2 2p6
LecturePLUS Timberlake

50. Example: Period 1 Configurations
In Period 1, the first two electrons enter the 1s orbital
LecturePLUS Timberlake

51. Abbreviated Configurations
An abbreviated configuration shows
The symbol of the noble gas in brackets that represents completed sublevels.
The remaining electrons in order of their sublevels,
Example: Chlorine has a configuration of
1s2 2s2 2p6 3s2 3p5
[Ne]
The abbreviated configuration for chlorine is
[Ne] 3s2 3p5
LecturePLUS Timberlake

52. Period 2 Configurations
Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
LecturePLUS Timberlake

53. TAPPS Learning Check
A. The correct electron configuration for nitrogen is
1) 1s2 2p ) 1s2 2s2 2p6 3) 1s2 2s2 2p3
B. The correct electron configuration for oxygen is
1) 1s2 2p ) 1s2 2s2 2p4 3) 1s2 2s2 2p6
C. The correct electron configuration for calcium is
1) 1s2 2s2 2p6 3s2 3p6 3d2
2) 1s2 2s2 2p6 3s2 3p6 4s2
3) 1s2 2s2 2p6 3s2 3p8
LecturePLUS Timberlake

54. TAPPS Learning Check A. Cl B. S C. K
Write the electron configuration and abbreviated configuration for each of the following elements:
A. Cl
B. S
C. K
LecturePLUS Timberlake

55. Sublevel Blocks on the Periodic Table
The periodic table consists of sublevel blocks
arranged in order of increasing energy.
Groups 1A-2A = s level
Groups 3A-8A = p level
Groups 3B to 2B = d level
Lanthanides/Actinides = f level
LecturePLUS Timberlake

56. Sublevel Blocks LecturePLUS Timberlake
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
LecturePLUS Timberlake

57. Writing Electron Configurations
Using the periodic table, write the electron configuration
for silicon.
Solution
Silicon is in group 4A, period 3, thus we would stop at 3p and it would have 2 electrons in the 3p orbital:
all the sublevel blocks in order gives:
1s2 2s2 2p63s2 3p2
LecturePLUS Timberlake

58. Electron Configurations d Sublevel
The 4s orbital has a lower energy than the 3d orbitals.
In potassium K, the last electron enters the 4s orbital instead of the 3d
1s 2s 2p 3s 3p 3d 4s
Ar 1s s2 2p6 3s2 3p6
K 1s s2 2p6 3s2 3p6 4s1
Ca 1s s2 2p6 3s2 3p6 4s2
Sc 1s s2 2p6 3s2 3p6 3d1 4s2
Ti 1s s2 2p6 3s2 3p6 3d2 4s2
LecturePLUS Timberlake

59. Exceptions in Sublevel Block Order
Within the filling of the 3d sublevel, exceptions occur for chromium and copper
Both Cr and Cu, in the 3d sublevel, are close to either a half-filled or filled sublevel
Cr has only 1 electron in the 4s and 5 e-s in the 3d sublevel …half-filled 3d, added stability
Cu has 1 e- in 4s and 10 e-s in 3d sublevel … completely filled 3d, stable
After 4s and 3d, 4p is filled

60. Writing Electron Configurations
Using the periodic table, write the electron configuration
for manganese.
Solution
1s2 2s2 2p63s2 3p6 4s2 3d5
LecturePLUS Timberlake

61. Learning Check A. The last two sublevel blocks in the electron
configuration for Co are
1) 3p64s2
2) 4s24d7
3) 4s23d7
B. The last three sublevel blocks in the electron
configuration for Sn are
1) 5s25p24d10
2) 5s24d105p2
3) 5s25d105p2
LecturePLUS Timberlake

62. Learning Check Give the symbol of the element that has A. [Ar]4s2 3d6
B. Four 3p electrons
C. Two electrons in the 4d sublevel
D. The element that has the electron configuration
1s2 2s2 2p6 3s2 3p6 4s2 3d2
LecturePLUS Timberlake

63. Pause: ALE 2
Group activity: all groups work on problems on ALE 2 worksheet, problems 12-15
Need volunteers to work on the problems written on the board. If no volunteers immediately, will call names. Everyone will do problems on the board sooner or later
While working on the problems, ask if you have any questions. I’m more than happy to help
LecturePLUS Timberlake

64. Lecture 2: Atoms and Elements
Periodic Trends
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

65. Valence Electrons The valence electrons
Determine the chemical properties of the elements.
Are the electrons in the highest energy level.
Are related to the Group number of the element.
Example: Phosphorus has 5 valence electrons
5 valence electrons
P Group 5A(15) s2 2s2 2p6 3s2 3p3
LecturePLUS Timberlake

66. Groups and Valence Electrons
All the elements in a group have the same number of
valence electrons.
Example: Elements in Group 2A(2) have two (2) valence electrons.
Be 1s2 2s2
Mg 1s2 2s2 2p6 3s2
Ca [Ar] 4s2
Sr [Kr] 5s2
LecturePLUS Timberlake

67. Periodic Table and Valence Electrons

68. Electron-Dot Symbols · Mg · or Mg · or · Mg or · Mg
An electron-dot symbol
Indicates valence electrons
as dots around the symbol of the element.
Of Mg shows two valence electrons as single dots on the sides of the symbol Mg.
· Mg · or Mg · or · Mg or · Mg
Electron-dot symbol
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

69. Writing Electron-Dot Symbols
The electron-dot symbols for
Groups 1A(1) to 4A(14) use single dots.
· ·
Na · · Mg · · Al · · C ·
Groups 5A(15) to 7A(17) use pairs and single dots.
· · · ·
· P · : O ·
· ·
LecturePLUS Timberlake

70. Learning Check State the number of valence electrons for each: A. O
1) ) 6 3) 8
B. Al
1) ) 3 3) 1
C. Cl
1) 2 2) 5 3) 7
LecturePLUS Timberlake

71. Learning Check State the number of valence electrons for each.
A. 1s2 2s2 2p6 3s2 3p1
B. 1s2 2s2 2p6 3s2
C. 1s2 2s2 2p5
LecturePLUS Timberlake

72. Groups and Electron-Dot Symbols
In a group, all the electron-dot symbols have the same number of valence electrons (dots).
Example: Atoms of elements in Group 2A(2) each have 2 valence electrons.
2A(2)
· Be ·
· Mg ·
· Ca ·
· Sr ·
· Ba ·
LecturePLUS Timberlake

73. Learning Check  A. X is the electron-dot symbol for 1) Na 2) K 3) Al
 
B.  X 
 is the electron-dot symbol of
1) B 2) N 3) P
LecturePLUS Timberlake

74. Atomic Size Atomic size is Described using the atomic radius.
The distance from
the nucleus to the
valence electrons.
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

75. Atomic Radius Within A Group
Increases going down each group of representative elements.
Decreases going across each period.
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings
LecturePLUS Timberlake

76. Ionization Energy Ionization energy
Is the energy it takes to remove a valence electron.
Na(g) + Energy (ionization) Na+(g) + e-
LecturePLUS Timberlake

77. Ionization Energy The ionization energies of Metals are low
Nonmetals are high
Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
LecturePLUS Timberlake

78. Pause: Group Work
Do all the problems in group activity 2 as group