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.
Atoms are electrically neutral.
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)
The charge on the nucleus is positive.
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
Also called the Nuclear Charge

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