1. Introductory Chemistry, 3rd Edition Nivaldo Tro
Intro to the
Periodic Table
And
Atoms
Vs.
Ions
Isotopes

2. The Modern Atom
Atoms are composed of three particles - protons, neutrons and electrons
The nucleus contains protons and neutrons
The electrons move outside the nucleus
Neutral atom has same # protons and electrons.

3. The Nuclear Atom:
protons
Nucleus
neutrons + -
electrons - +

4. Subatomic Particles: Charge? Location? neutrons (n) protons (p)
electrons (e)

5. Subatomic Particles: Charge? Location? neutron 0 nucleus proton
outside
neutron
proton
electron
Charge? Location?

6. Subatomic Particles:
Mass (amu) 1
 (1/1837)
neutron
proton
electron

7. Elements Each element has a unique number of protons in its nucleus
Number of protons in the nucleus of an atom is called the atomic number
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

8. How many? protons = depends on element
neutrons = variable for each element
electrons = same as protons

9. atomic number -
The number of protons in one atom; each element has a different atomic number
The number on top of the element symbol in the periodic table

10. The Periodic Table of Elements

11. Review What is the atomic number of boron, B?
What is the atomic mass of silicon, Si?
How many protons does a chlorine atom have?
How many electrons does a neutral neon atom have?
Will an atom with 6 protons, 6 neutrons and 6 electrons be electrically neutral?
Will an atom with 27 protons, 32 neutrons and 27 electrons be electrically neutral?
Will a Na atom with 10 electrons be electrically neutral?

12. Review What is the atomic number of boron, B? 5
What is the atomic mass of silicon, Si? amu
How many protons does a chlorine atom have? 17
How many electrons does a neutral neon atom have? 10
Will an atom with 6 protons, 6 neutrons and 6 electrons be electrically neutral? Yes
Will an atom with 27 protons, 32 neutrons and 27 electrons be electrically neutral? Yes
Will a Na atom with 10 electrons be electrically neutral? No

13. Three Types of Elements
= Metal
= Metalloid
= Nonmetal

14. Metals Solids at room temperature, except Hg Shiny
Conduct heat, electricity
Malleable: can be shaped
Ductile = drawn or pulled into wires
Lose electrons and form cations (+ charge) in reactions
About 75% of the elements are metals

15. Nonmetals Found in all 3 states Poor conductors of heat & electricity
Solids are brittle
Gain electrons in reactions to become anions (- charge)
Only a few on the right of periodic table

16. does not conduct heat well
Metalloids
Show some properties of metals and some of nonmetals
Also known as semiconductors
Properties of Silicon
shiny
conducts electricity
does not conduct heat well
brittle

17. The Modern Periodic Table
Elements with similar chemical and physical properties are in same column
Columns are called Groups or Families
designated by a number and letter at top
Rows are called Periods
Each period shows the pattern of properties repeated in the next period

18. The Modern Periodic Table
Main Group = Representative Elements = ‘A’ groups
Transition Elements = ‘B’ groups
all metals
Bottom rows = Inner Transition Elements = Rare Earth Elements
metals
really belong in Period 6 & 7

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

20. Important Groups - Hydrogen
nonmetal
colorless, diatomic gas
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
HX dissolves in water to form acids

21. Important Groups – IA, Alkali Metals
hydrogen usually placed here, though it doesn’t belong
soft, low melting points,low density
very reactive, never find uncombined in nature
tend to form water soluble compounds
react with water to form basic (alkaline) solutions and H2 releasing a lot of heat
lithium
sodium
potassium
rubidium
cesium

22. Important Groups – IIA, Alkali Earth Metals
harder, higher melting, and denser than alkali metals
reactive, but less than corresponding alkali metal
form stable, insoluble oxides from which they are normally extracted
oxides are basic = alkaline earth
beryllium
magnesium
calcium
strontium
barium

23. Important Groups – VIIA, Halogens
nonmetals
F2 & Cl2 gases; Br2 liquid; I2 solid
all diatomic
very reactive
react with metals to form ionic compounds
HX all strong acids except HF
fluorine
chlorine
bromine
iodine

24. 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

25. Charged Atoms = Ions
Number of protons (atomic #) identifies the element!
all sodium atoms have 11 protons in the nucleus
In chemical change, number of protons in nucleus of atom doesn’t change!
Atoms can lose or gain electrons becoming electrically charged, these are called ions

26. 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

27. Atomic Structures of Ions
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 be determined from the Group number on the Periodic Table
Group 1A  +1, Group 2A  +2, (Al, Ga, In)  +3

28. Atomic Structures of Ions
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-  O-2 oxide ion
Charge on an anion can be determined by subtracting 8 from the Group number on the Periodic Table
Group 7A  7- 8 = -1; Group 6A  6 – 8 = -2

29. Example:
Find the number of protons and electrons in the Ca2+ ion.

30. Find the number of protons, electrons, & neutrons or the chagre in the following ions:
Na+, O2- , Cl 17 protons & 18 electrons, Nitrogen 7 protons & 10 electrons

31. Ion Charge & the Periodic Table
Charge on an ion can often be determined from an element’s position on the Periodic Table
Metals are always positive ions, nonmetals are negative ions
For many main group metals, the charge = the group number
For nonmetals, the charge = the group number - 8

32. Charges of Main Group IonsIA
VIA
IIA
IIIA VA
VIIA
Li+1
Be+2
N-3
O-2
F-1
Na+1
Mg+2
Al+3
P-3
S-2
Cl-1
K+1
Ca+2
Ga+3
As-3
Se-2
Br-1
Rb+1
Sr+2
In+3
Te-2
I-1
Cs+1
Ba+2

33. Mass # Atomic # C. Isotopes Isotope symbol: “Carbon-12”
Atoms of the same element with different numbers of neutrons.
Isotope symbol:
Mass #
Atomic #
“Carbon-12”

34. Isotopes
Isotopes = atoms of an element that have same # of protons but different # of neutrons
Isotopes of an element have different masses
isotopes are identified by their
mass numbers = protons + neutrons
All isotopes of an element are chemically identical
undergo the exact same chemical reactions

35. Isotope Symbols
Cl-35 makes up about 75% of chlorine atoms in nature, and Cl-37 makes up the remaining 25%
Average atomic mass of Cl = amu
Cl-35 has a mass number = 35, 17 protons and 18 neutrons ( ) Cl 35 17
or Cl-35
X = Atomic Symbol
A = mass number
Z = atomic number AX Z

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

37. C. Isotopes
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38. C. Isotopes Average Atomic Mass reported on Periodic Table
weighted average of all isotopes
Or multiply the relative abundance (%) by the mass of that isotope.
Avg.
Atomic
Mass

39. C. Isotopes
EX: About 8 out of 10 chlorine atoms are chlorine-35. Two out of 10 are chlorine-37.
Avg.
Atomic
Mass
35.4 u

40. Neon 9.25% 22 12 10 Ne-22 0.27% 21 11 Ne-21 90.48% 20 Ne-20 Symbol
Percent Natural Abundance
Mass Number
Number of Neutrons
Number of Protons
Symbol