1. Subatomic Particles

2. 1. Subatomic Particles Particle Symbol (table O) Charge Mass (amu)
Location
Electrons e
0e-1
0β-1
Negative
(-1)
1/1872 amu
0 amu
Outside nucleus
(energy levels)
Protons p
1p1
1H1
Positive (+1)
1 amu
Nucleus
Neutrons n
1n0
Neutral
(0)

3. Special notes on subatomic particles
In a neutral atom # of protons=#of electrons.
If the number of protons does not equal the number of electrons you have a charged atom known as an ion.
# protons > # electrons forms a + ion (cation)
# electrons > # protons forms a – ion (anion)
Most of the mass of an atom is in nucleus.

4. Atomic Number (z) 1913—Henry Mosley Used to identify an atom
Indicates the number of protons
In a neutral atoms also gives the number of electrons

5. 3. Mass Number (A)
Total number of protons and neutrons in the nucleus of an atom. (nucleons)
Notation: AXZ
Mass # = #protons + # neutrons
# neutrons = Mass # - # protons

6. Try the following: Sample Atom Notation Protons (atomic #)
Neutrons (mass #-atomic #)
Electrons(same as atomic#)
Carbon-12
C-12
12C6 6
12-6=6
Chlorine-35 Cl-35
35Cl17 17
35-17=18
Chlorine-37
Cl-37
37Cl17
37-17=20
Neon-20 Ne-20
20Ne10 10
20-10=10
Oxygen-16 O-16

7. Determine the # of protons, neutrons, and electrons for these added examples:
24Mg12
12 protons
24-12=12 neutrons
12 electrons
24Mg12+2
12 neutrons
10 electrons

8. Isotopes
Thomson (1912) found 2 types of neon atoms and Soddy (1910) found 2 types of uranium atoms.
2 elements that have the same atomic number but different mass numbers
Based on atomic structure: 2 elements that have the same number of protons but different number of neutrons.
For example: Cl-35 and Cl-37

9. 5. Atomic Mass Decimal number
Average of all the naturally occurring isotopes for a particular element
If you round the atomic mass it gives you the mass number for the most common isotope.
Unit is amu (atomic mass unit)
1 amu is 1/12 the mass of C-12
Gram atomic mass= amu but in grams

10. Try the following:
Determine the number of protons, neutrons, and electrons for the following isotopes of hydrogen:
Solution:
Hydrogen-1 (protium) 1H1 1p,0n,1e
Hydrogen-2 (deuterium) 2H p,1n,1e
Hydrogen-3 (tritium) 3H p,2n,1e

11. Naturally occurring chlorine consists of 75% Cl-35 and 25% Cl-37
Naturally occurring chlorine consists of 75% Cl-35 and 25% Cl-37. Find the average atomic mass.
.75(35) + .25(37)= amu or
75(35) (37) =35.50 amu
100

12. 3. Calculate the atomic mass of an element with isotope A occurring 70
3. Calculate the atomic mass of an element with isotope A occurring 70.0% of the time with a mass of 13.0 amu and isotope B occurring 30.0% of the time with a mass of 15.0 amu.
.70 (13.0) (15.0) =13.6 amu

13. An element X has three isotopes X-30 has a 50
An element X has three isotopes X-30 has a 50.0% abundance, X-28 has a 30.0% abundance and X-31 has a 20.0% abundance.
.500(30) (28) (31) = 29.6 amu

14. 5. There are two isotopes of element Z, 60
5. There are two isotopes of element Z, 60.0% of the atoms have a mass of 58.0 amu and 40.0% have a mass of 57.0 amu. Calculate theatomic mass of element Z.
.600(58.0) (57) = 57.6 amu