1. Dmitri Mendeleev order elements by atomic mass
saw a 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
where atomic mass order did not fit other properties, he re-ordered by other properties

2. Periodic Table PatternH
nm H2O
a/b H2 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
nm O2
H2O O
nm OF2 HF F
left  right across a row (period) increasing atomic mass (not relative mass);
organized based on their activity and properties

3. Periodic Table PatternH
nm H2O
a/b H2 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
nm O2
H2O O
nm OF2 HF F Na
m Na2O b
23 NaH
m MgO b
24 MgH2 Mg
m Al2O3
a/b
27 (AlH3) Al
nm/m SiO2 a
28 SiH4 Si
nm P4O10 a
PH3 P
nm SO3 a
32 H2S S
nm Cl2O7 a
35.5 HCl Cl
up  down column; similar properties; how the elements react with H and O
some gaps were left in table for undiscovered elements; properties
of these elements were predicted.

4. Mendeleev's Predictions for Ekasilicon (Germanium)14
28.09 32
72.61 Ge Sn 50
118.71

5. PERIODIC TABLE
Non-metals
Metals
Metalloids

6. PROPERTIES OF METALS & NON-METALS
Mostly solid
Can be solid, liquid or gas
Have shiny appearance
Have dull appearance
Good conductors of heat & electricity
Poor conductors of heat & electricity
Malleable & ductile
Brittle (if solid)
Lose electrons
Gain or share electrons

7. Metals
Non-metals

8. METALLOIDS
Metalloids are elements that possess some properties of metals and some of non-metals.
The most important metalloids are silicon (Si) and germanium (Ge) which are used extensively in computer chips.

9. Metalloids
Properties of Silicon
shiny
conducts electricity
brittle

10. PERIODIC TABLE Metallic character decreases going across a period.
Metallic character increases going down a group F
Least metallic element Cs Fr
Most metallic elements

11. PERIODIC TABLE Seven elements exist as diatomic molecules.
All others exist as monatomic (single atom).

12. PERIODS & GROUPS
The periodic table is composed of periods (rows) and groups or families (columns).
Elements in the same family have similar properties, and are commonly referred to by their traditional names.

13. PERIODS & GROUPS
Group 2 elements are called alkaline-earth metals. These metals are less reactive than alkali metals.
The group of metals in between the main group elements are called transition metals.
Halogens are the most reactive nonmetals, and occur in nature only as compounds.
Noble gases are un-reactive gases that are commonly used in light bulbs.
Elements in groups 1-2 and are referred to as main-group or representative groups.
Alkali metals are soft metals that are very reactive. They often react explosively with other elements.

14. Important Groups - Hydrogen
nonmetal
colorless, diatomic gas
very low melting point & density
reacts with nonmetals to form molecular compounds
HCl is acidic gas and H2O is a liquid
reacts with metals to form hydrides (negative ion of hydrogen = H-)
metal hydrides react with water to form H2
(Metal-H + H2O H2 + metal-OH)
(NaH + HOH H2 + NaOH)

15. Important Groups – IA, Alkali Metals
hydrogen usually placed here, though it doesn’t belong
soft, low melting points,low density
flame tests ® Li = red, Na = yellow, K = violet
very reactive, never find uncombined in nature
tend to form water soluble compounds
lithium
sodium
potassium
rubidium
cesium

16. Important Groups – IIA, Alkali Earth Metals
harder, higher melting, and denser than alkali metals
flame tests ® Ca = red, Sr = red, Ba = yellow-green
reactive, but less than corresponding alkali metal
form stable, insoluble oxides from which they are normally extracted
oxides are basic = alkaline earth
reactivity with water to form H2,
beryllium
magnesium
calcium
strontium
barium

17. Important Groups – VIIA, Halogens
nonmetals
F2 & Cl2 gases; Br2 liquid; I2 solid
all diatomic
very reactive
react with metals to form ionic compounds
HX (X = halogen) are all acids
HF weak < HCl < HBr < HI
fluorine
chlorine
bromine
iodine

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

19. Atomic number (Z) = # of protons Mass number (A) = # of p+ + # of n0
ATOMIC STRUCTURE
The general designation for an atom is shown below:
Atomic number (Z) = # of protons
Mass number (A) = # of p+ + # of n0
# of n0 = A - Z

20. Charged Atoms 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

21. ELEMENTS & IONS
An ion (charged particle) can be produced when an atom gains or loses one or more electrons.
Metals form cations
A cation (+ ion) is formed when a neutral atom loses an electron
Cations are named the same as the parent atom
5.1

22. ELEMENTS & IONS
Anions are named by using the root of the parent atom’s name and changing the ending to –ide.
Chlorine changes to chloride
Non-metals form anions
An anion (- ion) is formed when a neutral atom gains an electron
5.1

23. Ion Charge & the Periodic Table
Every element wants to be like the noble gases
wants 0 or 8 valence electrons
valence e- (outer electron shell used for bonding)
He has zero valence e-

24. ELEMENTS & IONS
elements of Group IA have a +1 charge
elements of Group VIA have a -2 charge
elements of Group IIA have a +2 charge
elements of Group VIIA have a -1 charge
elements of Group VA have a -3 charge
For main-group elements, the charge of ions are very characteristic of the group numbers.

25. Structure of the Nucleus
( )
Frederick Soddy discovered that the same element could have atoms with different masses, which he called isotopes
there are 2 isotopes of chlorine found in nature, one that has a mass of about 35 amu and another that weighs about 37 amu
The observed mass is a weighted average of the weights of all the naturally occurring atoms
the atomic mass of chlorine is amu

26. Isotopes Atomic mass - The average mass for a given element
all isotopes of an element have the same number of protons
isotopes of an element have different masses
isotopes of an element have different numbers of neutrons
isotopes are identified by their mass numbers
protons + neutrons

27. ISOTOPES
Isotopes of an element have the same atomic number (Z), but a different mass number (A).
Atoms of the same element that possess a different number of neutrons are called isotopes.
The 3 isotopes of Hydrogen

28. ISOTOPES & ATOMIC MASS
The mass of an atom is measured relative to the mass of a chosen standard (carbon-12 atom), and is expressed in atomic mass units (amu).
The average atomic mass of an element is the mass of that element’s natural occurring isotopes weighted according to their abundance.
Therefore the atomic mass of an element is closest to the mass of its most abundant isotope.

29. 4.8 Isotopes: Natural Abundance
Isotopes of neon 
 Naturally occurring neon contains three different isotopes: Ne-20 (with 10 protons and 10 neutrons), Ne-21 (with 10 protons and 11 neutrons), and Ne-22 (with 10 protons and 12 neutrons).

30. Example 1:
Determine the number of protons, electrons and neutrons in a chlorine atom .
# of protons =
17 (Z)
# of electrons =
17 (= p+)
# of neutrons =
18 ( )

31. Example 2: Which two of the following are isotopes of each other?
Isotopes of an element have the same atomic number, but a different mass number

32. Example 3:
Based on the information below, which is the most abundant isotope of boron (atomic mass = 10.8 amu) ?
Isotope
10B
11B
Mass (amu)
10.0
11.0
Atomic mass of an element is closer to the mass of the more abundant isotope

33. CALCULATING MASS FROM ISOTOPIC DATA
Isotope
Mass
(amu)
Abundance (%)
107Ag
106.91
51.84
109Ag
108.90
48.16
(106.91)
(0.5184) =
55.42 amu
(108.90)
(0.4816) =
52.45 amu
amu

34. 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

35. THE END