1. Atoms & Elements

2. Chapter Outline Development of Atomic Theories The composition of Atom
Chemical properties of Atoms, the Periodicity and Periodic Table
Isotopes

3. Experiencing Atoms Atoms: incredibly small, yet compose everything
atoms are the pieces of Elements
properties of the atoms determine the properties of the elements

4. Experiencing Atoms 91 elements found in nature
Over 20 we have made in laboratories, and scientists are going to make more 
Each element has its own, unique kind of atoms
different structures
different properties

5. Dalton’s Atomic Theory
Elements are composed of atoms
All atoms of an element are identical
Atoms combine in simple, whole-number ratios to form molecules of compounds
CO2 (O=C=O): 2 Oxygen atom + 1 Carbon atom
H2O (H-O-H): 2 Hydrogen atom + 1 Oxygen atom
In chemical reactions, atoms are not broken or changed into another type
2H2 + O2  2H2O
John Dalton
( )

6. The Size of Atoms Atomic Mass Unit (amu): 1 amu = 1.66  10-24 g
Hydrogen the smallest atom
mass of H atom= 1.67 x 10-24g ~ 1 amu
volume of H atom = 2.1 x 10-25cm3

7. About Electric Charge
Rubbing dry paper towel and dry plastic piece causes plastic attracting small objects like styrofoam.
Benjamin Franklin:
Two Kinds of Charge: + and –
Opposite Charges Attract: + attracted to –
Like Charges Repel
+ repels +
– repels –
Neutral: no charge or equal amounts of opposite charges

8. Lightning: Neutralization of Charges accumulated between the clouds and the ground

9. 1900s: The Atom is Divisible!
Discovery of Electrons (J.J. Thomson et al.):
The atom had pieces called electrons
Electrons are much smaller than atoms and carry a “-” charge
the mass of the electron is 1/1836th the mass of a hydrogen atom
the charge on the electron is the fundamental unit of charge which we will call –1 charge units

10. What is Inside an atom. https://www. youtube. com/watch
What is Inside an atom? (7-10 min)
Ernest Rutherford’s experiment (1909): bombardment of a sheet of large atoms (as target) with small, high energy particles
bullet = alpha particles, target atoms = gold foil
a particles have a mass of 4 amu & charge of +2 c.u.
gold has a mass of 197 amu & is very malleable

11. Rutherford’s Experiment
Alpha Particles
Striking Screen
Radioactive
Sample
~2%
0.01%
>98%
Lead Box
Fluorescent
Screen
Gold
Foil

12. Rutherford’s Results
Thompson’s model of atom predicts there is no heavy mass or high charge within the atom, a particles should penetrate without obstruction
> 98% of the a particles: went straight through
~2% of the a particles went through but were deflected by large angles
~0.01% of the a particles bounced off the gold foil: “...as if you fired a 15” canon shell at a piece of tissue paper and it came back and hit you.”

13. Rutherford’s Model of Atoms: Nuclear Atom.
Atom mostly empty space
because almost all the particles went straight through
Atom contains a dense particle:
small in volume compared to the atom but large in mass
because of the few particles that bounced back
“+” charge
because of the large deflections of some of the particles

14. . Thompson’s Plum Pudding Atom was disproved by Experiment•
Plum pudding model:
all the a particles
should go
straight through
a few of the
a particles
do not go through .
Rutherford’s Nuclear Atom Model
most a particles
go straight through
some a particles
go through, but are deflected

15. Modern View of Atom Atoms = (Protons + Neutrons) + Electrons
Nucleus: Protons + Neutrons, about cm in diameter
Electrons move outside the nucleus with an average distance of about 10-8 cm
therefore the radius of the atom is about 100,000 times larger than the radius of the nucleus

16. Inside the Nucleus: Neutron and Protons
Protons: “+” charge and a mass of 1 amu
the number of proton equals the number of electrons in an atom (electrically neutral)
Neutron: have no charge and a mass of 1 amu
the masses of the proton and neutron are both approximately 1 amu

18. Elements each Element has a unique number of protons in its nucleus
Atomic number: the number of Protons in the nucleus of an atom
the elements are arranged on the Periodic Table in order of their atomic numbers
each element has a unique name and symbol
symbol either one or two letters
one capital letter or one capital letter + one lower case

19. The Periodic Table of Elements

20. Get to know Elements: Name, Symbol, Atomic Number
Element Name
Symbol
Atomic Number
Lead Sb 79

21. Mendeleev: Periodicity
order elements by atomic mass  repeating pattern of properties
Periodic Law – When the elements are arranged in order of increasing relative mass, certain sets of properties recur periodically
used pattern to predict properties of undiscovered elements
A good documentary: Mendeleev (in the first 25 minutes, min as my fav )

22. Periodic Pattern: Compound with oxygen (ExOy) or with hydrogen (EHx)
metal (m) or nonmetal (nm)
oxide: acidic (a) or basic (b) H
nm H2O
a/b H2
Compound w/ H Li
m Li2O b
7 LiH Be
m/nm BeO
a/b
9 BeH2
nm B2O3 a
11 (BH3)n B
nm CO2 a
12 CH4 C
nm N2O5 a
14 NH3 N O
nm OF2 HF F
nm O2
H2O Na
m Na2O b
23 NaH
m MgO b
24 MgH2 Mg Al Si
nm P4O10 a
PH3 P
nm SO3 a
32 H2S S
nm Cl2O7 a
35.5 HCl Cl
m Al2O3
a/b
27 (AlH3)
nm/m SiO2 a
28 SiH4

23. Periodicity
= Metal
= Metalloid
= Nonmetal

24. Metals: Physical vs. Chemical Properties
solids at room temperature, except Hg
reflective surface
shiny
conduct heat, electricity
Malleable (can be shaped)
Tend to Lose electrons and form Cations in reactions. Na  Na+ + e -
about 75% of the elements are metals
lower left on the table

25. Nonmetals: Physical vs. Chemical Properties
Elements found in all 3 states
poor conductors of heat or electricity
solids are brittle
Tend to gain electrons in reactions to become anions: Cl + e -  Cl-
upper right on the table
except H He C N O F Ne P S Cl Ar Se Br Kr I Xe At Rn

26. Metalloids: between Metals and Nonmetals
show some properties of metals and some of nonmetals
also known as semiconductors
VIIIA
IVA VA
VIA
Properties of Silicon
shiny
conducts electricity
does not conduct heat well
brittle
VIIA
IIIA B
IIB Si Ge As Sb Te Po

27. The Modern Periodic Table
Elements with similar chemical and physical properties are in the same column
Columns are called _________ or Families
designated by a number and letter at top
Rows are _______s
each period shows the pattern of properties repeated in the next period
Group
period

28. The Modern Periodic Table
Main Group = Representative Elements = ‘A’ Groups IA~VIIIA
Transition Elements = ‘B’ groups: IB~VIIIB
all metals
Bottom rows = Inner Transition Elements = Rare Earth Elements
metals
really belong in Period 6 & 7

29. = Alkaline Earth Metals
= Alkali Metals
= Alkaline Earth Metals
= Noble Gases
= Halogens
= Lanthanides
= Actinides
= Transition Metals
add pictures of elements from text

30. = Transuranium element
= Transition Metals
= Rare Earth Metals
= Transuranium element
add pictures of elements from text U

31. Important Element - Hydrogen
nonmetal
colorless, diatomic gas H2
very low melting point & density
reacts with Nonmetals to form molecular compounds
HCl is acidic gas
H2O is a liquid
reacts with Metals to form hydrides
metal hydrides react with water to form H2
Nickel-metal hydride (NiMH) used in rechargeable battery
HX dissolves in water to form acids

32. Important Groups – IA, Alkali Metals
Usually Hydrogen is included
All metals: soft, low melting points
Flame tests ® Li = red, Na = yellow, K = violet
Chemical Property:
Very reactive. React with water to form basic (alkaline) solutions and H2.
releases a lot of heat
Tend to form water soluble compounds, such as table salt and baking soda.
colorless solutions
lithium
sodium
potassium
rubidium
cesium

33. Important Groups – IIA, Alkali Earth Metals
Physical properties: harder, higher melting, and denser than alkali metals
flame tests ® Ca = red, Sr = red, Ba = yellow-green
Chemical properties:
reactive, but less than corresponding alkali metal
form stable, insoluble oxides. oxides are basic = alkaline earth
reactivity with water to form H2, ® Be = none; Mg = steam; Ca, Sr, Ba = cold water
beryllium
magnesium
calcium
strontium
barium

34. Important Groups – VIIA, Halogens
nonmetals
F2 & Cl2 gases; Br2 liquid; I2 solid
all diatomic (two atoms in one molecule)
very reactive
Cl2, Br2 react slowly with water
Cl2 + H2O ® HCl + HOCl
(chlorine water)
react with metals to form ionic compounds
HX all acids
HF weak < HCl < HBr < HI
fluorine
chlorine
bromine
iodine

35. Important Groups – VIIIA, Noble Gases
all gases at room temperature,
very low melting and boiling points
very unreactive, practically inert
very hard to remove electron from or give an electron to

36. Ion: Charged Atom The number of protons determines the element!
all sodium atoms have 11 protons in the nucleus
In a chemical change, the number of protons in the nucleus of the atom doesn’t change!
no transmutation during a chemical change!!
during radioactive and nuclear changes, atoms do transmute
Atoms in a compound are often electrically charged, these are called ions

37. Ions Atoms acquire a charge by gaining or losing electrons
not protons!!
Ion Charge = # protons – # electrons
ions with a + charge are called cations
more protons than electrons
form by losing electrons
ions with a – charge are called anions
more electrons than protons
form by gaining electrons

38. Atomic Structures of Cations
Metals form cations
More positive charge, the fewer electrons 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

39. Atomic Structures of Anions
Nonmetals form anions
For each negative charge the ion has 1 more electron than the neutral atom
F = 9 e-, F- = 10 e-
P = 15 e-, P3- = 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 be determined from the Group number on the Periodic Table
Group 7A  -1, Group 6A  -2

40. Example: Find the number of protons and electrons in the Ca2+ ion
The atomic number of Calcium is the number of ________ons.
The number of electrons in an ATOM equals the number of _____ons.
The “2+” charge means the ion has two _______ electrons
Therefore the number of electron in Ca2+ ion = ____ __ ____ = ___
number of protons = _____
Number of electrons = _____

41. Example: Find the number of protons and electrons in the Ca2+ ion
The atomic number of Calcium is the number of __protons.
The number of electrons in an ATOM equals the number of _protons.
The “2+” charge means the ion has two _fewer electrons
Therefore the number of electron in Ca2+ ion = 20 – 2 = _18__
number of protons = _20_
Number of electrons = 18

42. Example: Find the number of protons and electrons in an I- ion
The atomic number of iodine is the number of ________ons.
The number of electrons in an ATOM equals the number of _____ons.
The “-” charge means the ion has ONE _______ electrons
Therefore the number of electron in I- ion = ____ __ ____ = ___
number of protons = _____
Number of electrons = _____

43. Example: Find the number of protons and electrons in an I- ion
The atomic number of iodine is the number of _protons.
The number of electrons in an ATOM equals the number of _protons.
The “-” charge means the ion has ONE _more_ electrons
Therefore the number of electron in I- ion = = 54
number of protons = _53_
Number of electrons = _54_

44. Ion Charge & the Periodic Table
The charge on an ion: an elements position on the Periodic Table
Metals: always positive ions Na+ Ca2+ Al3+
Nonmetals are negative ions Cl- O2- N3-
Main group metals: #charge = #group
Magnesium ion = #Group = ______
Nonmetals, #ch
Phosphide ion = #group – 8 = _____

45. Charge of ions by Group __ __ __ __ __ __ IA VIA IIA IIIA VA VIIA Li+
__ __ __ __ __ __ IA
VIA
IIA
IIIA VA
VIIA
Li+
Be2+
N3-
O2- F-
Na+
Mg2+
Al3+
P3-
S2-
Cl- K+
Ca2+
Ga3+
As3-
Se2-
Br-
Rb+
Sr2+
In3+
Te2- I-
Cs+
Ba2+

46. Same Element, Different #Neutrons?
Isotopes: The same element could have atoms with different masses
2 isotopes of chlorine found in nature: one has a mass of about 35 amu (Cl-35); another that weighs about 37 amu (Cl-37)
Carbon-12 is much more abundant than Carbon-13. C-14 formed from nuclear reaction of N-14.
The observed mass is a weighted average of the weights of all the naturally occurring atoms
the atomic mass of chlorine is amu

47. Isotopes all isotopes of an element: chemically identical
undergo the exact same chemical reactions
the same number of protons
different masses due to different numbers of neutrons. Example: C-14 atom has eight neutrons; C-12 atom has six neutrons.
identified by their mass numbers
protons + neutrons

48. Isotopic Symbol
Cl-35 has a mass number = 35, 17 protons and 18 neutrons ( ). The symbol for this isotope would be Cl 35 17
Atomic Symbol
A = mass number
Z = atomic number
#neutrons = A - Z AX Z

49. Write the Isotopic symbol for Cr isotope w/ 27 neutrons
Write down the given quantity, questions, and equations
Given: Element, #neutron (#n)
Find: #proton (#p)
Find: #mass (A)
Given: #p = Z, A = #p + #n
#protons = _____
#mass = _____

50. Example: How many protons and neutrons in the chromium isotope

51. Practice - Complete the following table

52. Mass Number is Not the Same as Atomic Mass
the atomic mass is an experimental number determined from all naturally occurring isotopes
the mass number refers to the number of protons + neutrons in one isotope
natural or man-made

53. From Atom to Ion
Atom has equal number of positive charge (from protons) and negative charge (from electrons). Example:
A calcium atom (symbol “Ca”) has 11 protons and 11 electrons
A chlorine atom (Cl) has 17 protons and 17 electrons
Metal loses electrons and becomes an ion with positive charge. A Ca atom loses TWO electrons, giving an ion with two positive charge: Ca2+
Nonmetal gains electrons and becomes an ion with negative charge. A Cl atom gains ONE electron, giving an ion with one negative charge: Cl-

54. Common Metal Cation Charge = + #Group
Remember the following metal ions:
Group IA = +1
Lithium ion ____ Potassium ion _____
Group IIA = +2
Magnesium ion ____ Barium ion _____
Silver ion:____ Zinc ion: ____ Aluminum: ____

55. Monatomic Nonmetal Anion (An-)
The charge = #Group – 8
Name of the anion: change ending on the element name to –ide
Group VA = -3
Group VIA = -2
Group VIIA = -1
N3-
____________
Oxide F-
_______________
_______
Phosphide
S2-
__________
Chloride

56. Simple and Weighted Averages

57. Atomic Mass is the Weighted average of Mass Number
Natural abundance of isotope: The percentage of #atoms for an isotope among all the naturally existing isotopes.
Gallium: Ga-69 (mass number amu, abundance 60.11%); Ga-71 (mass number , abundance 39.89%).
Atomic mass of Gallium = amu x x = amu

58. The Periodic Table

59. Chemistry Connection: Heavy Water