1. The Atom Chapter 2

3. Atom: basic unit of matter
Smallest unit of matter that individually retains the chemical characteristics of an element
Consists of a dense central region, called a nucleus, surrounded by a negatively charged cloud
Contains three types of subatomic particles:
Proton
Neutron
Electron

4. The Proton Charge = + 1.602×10−19 C Called “+1” for clarity
Located in nucleus of atom
Mass = x 10–24 g
Approx. 1 unified atomic mass unit (u)
1 u = 1.66 x 10–24 g
1/12 the weight of a Carbon- 12 atom

5. The Neutron No charge (0 C) Located in nucleus Mass = 1.675 x 10–24 g
Approx. = 1 u

6. The Electron Charge = –1.602 x 10–19 C Called “–1”
Located outside nucleus in an e- “cloud”
Mass = x 10-28g
Approx. = 0 u

7. Plum Pudding Model
J.J. Thomson
1904

8. Gold Foil Experiment Ernest Rutherford 1909
Proved J.J. Thomson’s theory wrong
Evidence for existence of protons

10. The Modern Atom
We know atoms are composed of three main pieces—protons, neutrons, and electrons.
The nucleus contains protons and neutrons.
The nucleus is only about cm in diameter.
The electrons move outside the nucleus with an average distance of about 10-8 cm.
Therefore, the radius of the atom is about 105 times larger than the radius of the nucleus.
Tro's "Introductory Chemistry", Chapter 4

11. 2.2 Structure of the Atom
All matter is composed of the same basic building
blocks called atoms.
Atoms are composed of three subatomic particles:

13. Dmitri Mendeleev (1834-1907) Russian chemist
Arranged elements in horizontal rows in order of increasing atomic weight
Started new rows in order to make columns of chemicals with similar characteristics
Left spaces open for elements yet to be discovered

14. Mendeleev's Predictions for Ekasilicon (Germanium)
Tro's "Introductory Chemistry", Chapter 4

20. = Alkali metals = Alkali earth metals = Noble gases = Halogens
= Lanthanides
= Actinides
= Transition metals
add pictures of elements from text
Tro's "Introductory Chemistry", Chapter 4

21. Metals Shiny Conduct electricity Ductile Can be drawn through wires
Malleable (Shapeable)
High M.P. & B.P
room temp
Except Hg

22. Non-Metals Don’t tend to conduct well Not usually ductile
Tend to be brittle
Low M.P. & B.P.
Many are gases at r.t.

23. Metalloids
Have chemical characteristics in between those of metals and non-metals
Includes elements: B (Boron), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), Polonium (Po), Astatine (At)

24. Alkali Metals Group 1 (1A) Li, Na, K etc. Soft, shiny metals
Conduct heat and electricity
React violently with H2O
Form H2(g) and alkaline (basic) solutions

25. Akali(ne) Earth Metals
Group 2 (2A)
Be, Mg, Ca etc.
Not as reactive as Alkali Metals, but still quite reactive
Tend to make basic solutions when placed in water

26. Transition Metals Groups 3-12 Tend to have high densities and B.P.
All are metals
Often used for electrical conduction
Often have vivid colors when in solution
Used for pigments

27. Colors of Transition Metal Compounds
Nickel
Cobalt
Copper
Zinc
Iron

28. Lanthanides Elements 57-71 Lanthanum (La) to Lutetium (Lu)
Commonly used in lasers
Can deflect UV and infrared rays

29. Actinides/Actinoids Elements 89-103 Actinium (Ac) to Lawrencium (Lr)
Only Actinium, Thorium (Th), and Uranium (U) occur naturally
Others created by neutron bombardment
Radioactive

30. Groups 13(3A) – 16(6A) No common name
Boundary between metals and non-metals occurs here
Contain elements abundant in earth’s crust, atmosphere, and living things
Contains the metalloids

31. Halogens Group 17 (7A) Love to form salts with metals
NaCl, KBr, CaCl2
Like to form diatomic molecules
F2, Cl2, Br2

32. Noble Gases Group 18 (8A) Very unreactive
Don’t like to bond to other molecules
Generally not abundant

33. Which atom does the picture below represent?

34. Atomic #
# of protons
Atomic symbol
Atomic Mass
Atomic Weight
Mass #
Molar Mass

36. Identify the atomic mass, number of protons, and number of neutrons for the following elements.

37. Ions Atoms acquire a charge by gaining or losing electrons.
Not protons!
Ion charge = # protons – # electrons.
Ions with a positive charge are called cations.
More protons than electrons.
Form by losing electrons.
Ions with a negative charge are called anions.
More electrons than protons.
Form by gaining electrons.
Chemically, ions are much different than the neutral atoms.
Because they have a different structure.
Tro's "Introductory Chemistry", Chapter 4

38. Atomic Structures of Ions
Nonmetals form anions.
For each negative charge, the ion has 1 more electron than the neutral atom.
F = 9 p+ and 9 e; F─ = 9 p+ and 10 e.
P = 15 p+ and 15 e; P3─ = 15 p+ and 18 e.
Anions are named by changing the ending of the name to –ide.
fluorine F + 1e  F─ fluoride ion
oxygen O + 2e  O2─ oxide ion
The charge on an anion can often be determined from the group number on the periodic table.
Group 7A  1, Group 6A  2.
Tro's "Introductory Chemistry", Chapter 4

39. Atomic Structures of Ions, Continued
Metals form cations.
For each positive charge the ion has 1 less electron than the neutral atom.
Na atom = 11 p+ and 11 e; Na+ ion = 11 p+ and 10 e.
Ca atom = 20 p+ and 20 e; Ca2+ ion = 20 p+ and 18 e.
Cations are named the same as the metal.
sodium Na  Na+ + 1e sodium ion
calcium Ca  Ca2+ + 2e calcium ion
The charge on a cation can often be determined from the group number on the periodic table.
Group 1A  1+, Group 2A  2+, (Al, Ga, In)  3+.
Tro's "Introductory Chemistry", Chapter 4

40. Isotopes Atoms of the same element that have different atomic masses
Same number of protons
Different # of neutrons

42. 2.3 Isotopes A. Isotopes, Atomic Number, and Mass Number
Isotopes are atoms of the same element that have
a different number of neutrons.
the number of protons (Z)
Mass number (A) = +
the number of neutrons
Mass number (A) 35 37
Mass number (A) Cl Cl
Atomic number (Z) 17 17
Atomic number (Z)
# of protons = 17
# of protons = 17
# of electrons = 17
# of electrons = 17
# of neutrons = 35 – 17 = 18
# of neutrons = 37 – 17 = 20

43. 2.3 Isotopes B. Atomic Weight
The atomic weight is the weighted average of the
masses of the naturally occurring isotopes of a
particular element reported in atomic mass units.
From the periodic table: 6 C
12.01
atomic number
element symbol
atomic weight (amu)

44. If it is a neutral atom, it will have 20 electrons.
Practice—An Atom Has 20 Protons. Determine if Each of the Following Statements Is True or False?
If it is a neutral atom, it will have 20 electrons.
If it also has 20 neutrons, its mass will be approximately 40 amu.
If it has 18 electrons, it will have a net 2 charge.
True
True
False
Tro's "Introductory Chemistry", Chapter 4

45. Diatomic Molecules
Dinitrogen (N2)
Molecules consisting of only two atoms of either the same or different elements O2 CO
Homonuclear Diatomic Molecule: a molecule made of two atoms of the same element H2
Heteronuclear Diatomic Molecule: a molecule made of two atoms that are different elements NO

46. Diatomic Elements Certain elements occur as diatomic molecules.
7 diatomic elements—The Rule of 7s
Find the element with atomic number 7, N.
Make a figure 7 by going over to Group 7A, then down
The seventh element is H2. 7A 7 H2
N2 O F2
Cl2
Br2 I2

47. Allotropism
The existence of multiple pure forms of an element, in the same phase (solid, liquid, or gas), that differ in structure
Different forms are called allotropes
Can exhibit varied physical properties and chemical behaviors
Don’t confuse allotropes with isotopes!!! O2 O3

49. Atomic Orbitals and Electron Configurations

50. Atomic Orbitals
Orbital: a specific region in an atom thought to posses the highest probability of containing the electron in question at any one time
Only hold maximum of two electrons at a time
4 basic types: s, p, d, f

51. The shells are numbered n = 1, 2, 3, etc.
2.5 Electronic Structure
An electron is confined to a specific region around the nucleus, giving it a particular energy.
The regions occupied by electrons are called
principal energy levels or shells (n).
The shells are numbered n = 1, 2, 3, etc.
Electrons in lower numbered shells are closer to
the nucleus and are lower in energy.
Electrons in higher numbered shells are further
from the nucleus and are higher in energy.

52. S orbitals
Spherical shape
Lowest energy of the orbitals

53. P Orbitals Higher energy than s orbitals Dumb bell shaped Come in 3’s
px, py, pz

54. D Orbitals Higher energy than s and p orbitals
Double dumb bell shape or single dumb bell with a donut
Come in 5’s
dxy, dxz, dyz, dx2-y2, dz2

55. F Orbitals
Higher energy than s, p, and d
Come in 7’s

57. How do we know where our electrons are?
Electrons will seek the lowest E orbital available first

58. Hydrogen Helium Lithium? 1
Pauli Exclusion Principle: orbitals may hold up to two electrons. The electrons must be of opposite spin

59. Hund’s Rule: electrons pair only after each orbital of equal energy is occupied by a single electron

61. 2.6 Electron Configuration B. Second-Row Elements (Period 2)
Orbital
Notation
Electron
Configuration
Element
Li (Z = 3)
3 electrons
1s22s1 1s 2s
C (Z = 6)
6 electrons
1s22s22p2 1s 2s 2p
Ne (Z = 10)
10 electrons
1s22s22p6 1s 2s 2p

62. 2.6 Electron Configuration
The electron configuration can be shortened by using Noble Gas Notation.
Write the Symbol of the previous Noble Gas, then add the electronic configuration of the additional electrons.
Electron
Configuration
Noble Gas
Notation
element: C
1s22s22p2
[He]2s22p2
nearest
noble gas: He
1s2

63. 2.6 Electron Configuration C. Other Elements
Orbital
Notation
Element Ca
20 electrons 1s 2s 2p 3s 3p 4s
4s is lower in energy;
it is filled before 3d.
Electron
Configuration
Noble Gas
Notation
1s22s22p63s23p64s2
[Ar]4s2

64. Problems
Determine the electron configurations for the following atoms. Use the noble gas configuration if needed. N O Na Mg S W

65. Exceptions to the RulesCr Cu

66. 2.7 Valence Electrons
The chemical properties of an element depend on the number of electrons in the valence shell.
The valence shell is the outermost shell (the highest value of n).
The electrons in the valence shell are called valence electrons. Be Cl
1s22s2
1s22s22p63s23p5
valence shell: n = 2
valence shell: n = 3
# of
valence electrons = 2
# of
valence electrons = 7

67. 2.7 Valence Electrons A. Relating Valence Electrons to Group Number
Elements in the same group have similar electron configurations.
Elements in the same group have the same number of valence electrons.
The group number, 1A–8A, equals the number of valence electrons for the main group elements.
The exception is He, which has only 2 valence electrons.
The chemical properties of a group are therefore very similar.

68. 2.7 Valence Electrons A. Relating Valence Electrons to Group Number
Period 1: H
1s1 He
1s2
Period 2: Li
2s1 Be
2s2 B
2s22p1 C
2s22p2 N
2s22p3 O
2s22p4 F
2s22p5 Ne
2s22p6
Period 3: Na
3s1 Mg
3s2 Al
3s23p1 Si
3s23p2 P
3s23p3 S
3s23p4 Cl
3s23p5 Ar
3s23p6

69. 2.8 Periodic Trends A. Atomic Size
The size of atoms
increases down a
column, as the
valence e− are
farther from the
nucleus.
Increases
Decreases
The size of atoms decreases across a row, as the number of protons in the nucleus increases, pulling the valence electrons in closer.

70. 2.8 Periodic Trends B. Ionization Energy
The ionization energy is the energy needed to remove
an electron from a neutral atom.
Na energy Na e–
Decreases
Ionization energies
decrease down a
column as the
valence e− get
farther away from
the positively charged nucleus.
Increases
Ionization energies increase across a row as the
number of protons in the nucleus increases.

71. Review Problems
Which of the following is considered qualitative data and which is quantitative?
Temperature
Creepiness
Juan likes to drive fast. If he regularly speeds along at 160 km/hr, how quickly is he going in miles/hr? In in/s?

72. You have a box that emits a wave that has a wavelength of 5.0 x 10-7 m. Using the electromagnetic spectrum below, predict what comes out of this box.

73. In the Macy's Thanksgiving day parade, 2009, a Smurf made his debut
In the Macy's Thanksgiving day parade, 2009, a Smurf made his debut. His white cap contained  36,763 L of helium and it was about 1/10 of his body size. Using this information, calculate the volume of the entire float. If the density of helium is  g/cm3, what is the mass of the helium for the entire float in kg? 

74. Identify which of the following are heterogeneous mixtures and which are homogeneous mixtures (solutions)
Jim Beam
Orange juice
Chicken noodle soup
7 up (fresh)
Blood
Clorox bleach

75. What are the electron configuration and orbital box diagram for Phosphorous?
Which element has the chemical symbol Ag?
What are the electron configuration and orbital box diagram for Ag?