1. Atoms & Elements

2. What is an atom?
An atom is the smallest particle of an element that retains its identity in a chemical reaction.
Word origin: atom comes from the Greek word atomos meaning “ indivisible”

3. Elements & Compounds
What would atoms of an element, mixture and compound look like at a microscopic level?

4. Subatomic Particles The parts that make up an atom! protons neutrons
electrons
electron
proton
nucleus
neutron

5. Subatomic Particles Electrons Protons Neutrons Found in the nucleus
Identifies the element
#of protons = specific element
Responsible for chemical and physical properties
Spin around in set regions outside of nucleus
Most important in chemical reactions
Farthest electron away from nucleus determines how atoms chemical to combine to one another.
Found in the nucleus
Plays no role in chemical behavior
Purpose: to put space between protons

6. Subatomic Particles How big is an atom?
Name
Symbol
Charge
Relative Mass
Proton p+ +1 1
Neutron no
Electron e- -1
0 (1/1840)
How big is an atom?
Imagine the nucleus is the size of a marble
located in the middle of the football field,
the electron would be in the classroom the size of a period!

7. Periodic Table
Greatest Cheat Sheet Ever!

8. Periodic Table Categories: Rows: periods Columns: groups or families
Metals
Nonmetals
Metalloids
(B, Si, Ge, As, Sb, Te, At)
Rows: periods
7 periods
Columns: groups or families
18 Groups
1A: Alkali Metals
2A: Alkaline Earth Metals
7A: Halogens
8A: Noble gases
B Groups: Transition and Inner Transition Metals

9. Si Periodic Table 14 Silicon 28.086 Atomic Number Symbol Element name
Atomic Mass

10. Si Important Numbers Atomic Number 14 Silicon has 14 protons
Counts the number of protons in an atom within the nucleus
Atomic Number
= # of protons 14 Si
Silicon has 14 protons

11. Atomic Number A. Nitrogen B. Potassium C. Neon
State the number of protons for atoms of each of the following:
A. Nitrogen
B. Potassium
C. Neon

12. Atomic Number A. Nitrogen B. Potassium C. Neon 7 protons 19 protons
State the number of protons for atoms of each of the following:
A. Nitrogen
7 protons
B. Potassium
19 protons
C. Neon
10 protons

13. Number of Electrons An atom is neutral The net charge is zero
Number of protons = Number of electrons
Atomic number = Number of electrons
Remember: proton = +1 electron = -1

14. Number of Electrons 14 Si
14 electrons
14 protons
-14
+14
= 0 neutral

15. Si Important Numbers Mass Number 14 Atomic Mass Silicon 28.086
Counts the number of protons and neutrons in an atom OR
Determined by: the whole number closest to the Atomic Mass

16. Si 28 14 Mass Number silicon-28 Show the mass number and atomic number
Atomic Symbols
Show the mass number and atomic number
Give the symbol of the element
Mass Number 28 14 Si
silicon-28
Atomic Number

17. Determine the Mass Numbers4 Be
9.0122 27 Co
58.933 10 Ne
20.179 9 59 20

18. Write the Symbol and Name for each4 Be
9.0122 27 Co
58.933 10 Ne
20.179 Be 9 4 59 27 Co 20 10 Ne
beryllium-9
cobalt-59
neon-20

19. Mass Number O P Zn The total number of particles in the nucleus
# of protons + # of neutrons
To determine the number of neutrons
Mass number – Atomic number = # of neutrons O 16 8 31 15 65 30 #p #n #e P Zn
8p+
30p+
15p+
8no
35no
16no
8e-
30e-
15e-

20. Isotopes
The atomic number identifies the element, but an element may have atoms with several different mass numbers.
Most elements consist of several different isotopes
Same number of protons , Different number of neutrons 35 17 Cl 37 17 Cl
chlorine-35
chlorine-37

21. Isotopes of Hydrogen
Naturally occurring hydrogen consists of 3 isotopes, protium (H-1), deuterium (H-2), and tritium (H-3). State the number of protons, neutrons, and electrons. 1 2 3 #p #n #e H H H 1 1 1 1 2 1 1 1

22. An atom of Calcium (Ca-40)
A. Number of protons
B. number of neutrons
C. What is the mass number of a calcium isotope with 19 neutrons?

23. Atomic Mass This is NOT a whole number
A given element can have atoms with several different mass numbers.
Average mass of the atoms with all possible mass numbers
We will calculate later 

24. Write the atomic symbol
A. 11p+, 12no, 11e-
B. 17p+, 20no, 17e-
C. 47p+, 60no, 47e-

25. Write the atomic symbol23 11 Na
A. 11p+, 12no, 11e-
B. 17p+, 20no, 17e-
C. 47p+, 60no, 47e- 37 17 Cl
107 47 Ag

26. Ions Na1+ Cl1- Atoms with a charge (positive or negative)
Remember atoms are neutral, therefore if an atom has a charge we call it an ion.
Ions- Atoms which gain or lose an electron
atom ion
#p 11 11
#e 11 10
#p 17 17
#e 17 18
Why do the electrons change?
Na1+
Cl1-

27. Why? If protons change…new______?________
If neutrons change…new______?______
If electrons change….new _____?______

28. Why?
If protons change…new element
If neutrons change…new isotope
If electrons change….new ion

29. Ions
atom ion #p #e #p #e
Mg 2+
O 2-

30. Complete Atomic Symbol combines isotopes and ions27 13
Al 3+
What does each represent?
How many of what subatomic particles does each represent?

31. Complete Atomic Symbol combines isotopes and ions27 13
Al 3+
Ionic charge
Mass number
Atomic number
14no
13p+
10e-

32. How many protons, neutrons, & electrons?65 30 14 7 32 15
N3-
Zn2+
P3-
30p+ 35no 28e-
7p+ 7no 10e-
15p+ 17no 18e-

33. Atomic Mass
Coming back to this…
Atomic mass is the weighted average mass of all the atomic masses of the isotopes of that atom.
So we involved all the different forms of ATOMS of an element (ions not an issue here) and how frequent they are

34. Average Atomic Mass cont.
To find the Average Atomic Mass (generally referred to as the atomic mass of an element) we need to use two things
The mass of the isotope
Multiplied by its frequency
Then we add all the forms up.

35. Example of Average Atomic Mass
Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine.
35 x =
100
35.5
37 x =
Add Us Up

36. Rubidium has two common isotopes, Rb-85 and Rb-87
Rubidium has two common isotopes, Rb-85 and Rb-87. If the abundance of Rb-85 is 72.2% and the abundance of Rb-87 is 27.8%, what is the average atomic mass or rubidium?