1. Chapter 17 Properties of Atoms
The Elements: Forged in Stars
The Origin of the Elements

2. The subatomic particles: protons, neutrons, & electrons
Name
Symbol
Charge
Location
Proton p+
positive
nucleus
Neutron n0
no charge
Electron e-
negative
charged cloud

3. Chemical Symbols Correct symbols are KEY Elements
Capitalization
No cursive
Spacing
Subscript (small low #)
Superscript (small upper #)
Elements
ALWAYS start with a capital letter
Symbols can be 1, 2, or 3 letters
1st letter is capitalized and 2nd & 3rd are lowercase
CO doesn’t equal Co
CO = Carbon monoxide
Co = Cobalt

4. x Symbols Mass # Charge Atomic # “Z” Number of atoms
Any element symbol

5. Using the Periodic Table (PT)
Atomic Number: The whole # in the box
Equal to the number of protons of an element
Always smaller than atomic mass
Atomic Mass: The larger number in the box
Usually has a decimal
Weighted average mass of all isotopes of that element
Mass number: NOT on the PT—Equal to the # of protons & neutrons in a specific isotope.

6. Atoms: by the NUMBERS Atomic # = p+
e- = p+ (For neutral atoms--ions are different)
Mass # = p+ + n0
n0 = Mass # – p+

8. Bohr Diagrams The # of protons are shown in the middle
Total # of electrons are shown as dots in rings around the nucleus.
2 e- in the first ring
8 in the 2nd ring
18 in the 3rd ring
Outermost ring(s) don’t need to be filled

9. Valence Electrons: Electrons in the outermost energy level (ring)
Most important e-
The e- used in bonding
Written below each group on the PT

10. Dots are placed in 8 positions around the symbol (max. of 8 dots)
Electron Dot Diagrams
Use the elemental symbol and dots to illustrate the # of valence electrons only
Dots are placed in 8 positions around the symbol (max. of 8 dots)
2 e- for each Right, Left, Top, & Bottom
e- are not paired until there is1 on each side
7 valence e-

11. Bohr vs Electron Dot Diagrams
Shows the TOTAL # of e- of the element surrounding the # of p+
Electron Dot:
Shows ONLY the VALENCE e- of the element around the element symbol
Maximum of 8 dots +8
Oxygen
Oxygen

12. Isotopes
Atoms of the same element (same # of protons) with different numbers of neutrons in the nucleus
This causes a difference in the mass of the atom
Isotopes are like different flavors of each element
Atoms with too few or too many neutrons can exist for a while, but they are unstable or radioactive

13. More about Atomic Mass
The atomic mass has a decimal because it is an average of the isotopes’ abundance
The atomic mass is always closest to the most abundant isotope
The one that exists most in nature
Video: Isotopes & Average Atomic Mass

15. The Periodic Table
Periodic Table—organized list of elements arranged according to their properties.
The 1st person to organize elements was Russian Dmitri Mendeleev in the 1800s.
Mendeleev organized the elements by atomic mass & left spaces for unknown elements.

16. The Modern Periodic Table
Mendeleev’s table was mostly correct, but it is more accurate to organize by atomic number.

17. Groups & Periods
Groups (or families)—vertical columns on the periodic table.
They are numbered 1-18.
Elements in each group have similar properties.

18. Periods—horizontal rows of elements on the periodic table.
Numbered 1-7
Elements increase by 1 p+ as you move left to right across a period.

19. Metals First metal used was gold – 6000 years ago
Followed by Cu, Ag, Sn, Fe
Mercury (Hg) is the only metal that is a liquid at room temp
Most reactive metals are Alkali Metals

20. Most elements are metals.
found to the LEFT of the Zigzag Line
Physical Properties:
Luster (shininess)
Good conductors of heat & electricity
High density (heavy for their size)
High melting point
Ductile (drawn into thin wires)
Malleable (hammered into thin sheets)
Chemical Properties:
Easily lose e-
Corrode easily

21. NONMETALS Nonmetals gain electrons to become stable
Found to the RIGHT of the zigzag line Except H
Important nonmetals in Humans:
Carbon, Hydrogen, Nitrogen, & Oxygen
Properties
Most are gases at room temp
Low density & melting point
Not malleable
Not ductile
Poor conductors of heat and electricity
No Luster – Dull
Nonmetals gain electrons to become stable

22. Group 17—Halogens Most reactive nonmetalsF
Most reactive nonmetals
Fluorine (F) is the most chemically active of ALL elements on the PT.
Only liquid nonmetal is Bromine (Br) Br

23. Group 18 – Noble Gases
THEY DO NOT FORM IONS because they have a full set of valence electrons
8 valence e- (for most)
2 valence e- (for He)

24. Metalloids Elements that border the Zigzag Line
Physical Properties of Metalloids:
Have properties of both metals & nonmetals
All are solids
Can be shiny or dull
Ductile & Malleable
Conduct heat & electricity better than nonmetals but not as well as metals

25. Meet the Elements
The element song
The Atom Song