1. The Atom & Subatomic Particles

2. What we knew by 1932: 1.0087 amu (or 1 amu) neutron 1n 1.0073 amu +1
neutron 1n
amu +1
proton 1p or 1H
amu
(or 0 amu) -1
electron 0e
Relative Mass
Relative Charge -1 1 1

3. Location of Subatomic Particles
electrons located outside nucleus
protons & neutrons located inside nucleus

4. Atomic Number atomic number: For neutral atoms:
= size of nuclear charge
= number of protons in nucleus
determines identity of element
gives order to PT
For neutral atoms:
atomic number = # protons = # electrons

5. Mass Number =
# protons # neutrons

6. Isotopes atoms of same element can have different mass numbers
# protons must be the same so …
# neutrons must be different

7. Dalton’s theory must be modified:
the atom is divisible
presence of subatomic particles
atoms of same element can be different
isotopes have different # neutrons

8. Notation 12C 6 left superscript is mass number
left subscript is atomic number

9. Notation 12C 6 How many neutrons in this atom?
12 = # protons + neutrons
6 = # protons
12C 6
How many neutrons in this atom?
12 – 6 = 6 neutrons

10. Mass number is ?
Atomic number is ?
# of neutrons is ?
# of electrons in atom is?
17O 8 17 8
= 9
17 – 8 8

11. 15 N
Mass number is ?
Atomic number is ?
# of neutrons is ?
# of electrons in atom is? 7 15 7
15 – 7
= 8 7

12. F 19 Mass number is ? Atomic number is ? # of neutrons is ?
# of electrons in atom is? 19 9
19 – 9 = 10 9

13. Other Notations
C-12
# after symbol is mass number!
must look up atomic number

14. What’s the difference between H-1, H-2, and H-3?
All H’s have 1 proton
H-1: mass # = 1
1 proton, ? neutrons
H-2: mass # = 2 1
1 proton, so it must have ? neutrons
H-3: mass # = 3 2
1 proton, so it must have ? neutrons

15. Consider U-234, U-235, & U-238 What’s the atomic number of U?
How many protons in U?
How many neutrons in U-234?
How many neutrons in U-235?
How many neutrons in U-238?
How many electrons in U? 92 92
234 – 92 = 142
235 – 92 = 143
238 – 92 = 146 92

16. How many neutrons in Po-217?
What’s the atomic number?
How many protons?
So the neutrons are … 84 84
217 – 84 = 133 neutrons!

17. IONS IONS = atoms that gained or lost electrons
protons and electrons aren't = anymore, so ions are not neutral they carry a charge (+/-)

18. IONS Charge of ion: = # protons minus # electrons
(subtract the electrons since are negative)

19. IONS
If atom loses electrons, it has more (+) protons than (-) electrons
What kind of ion is it?
If atom gains electrons, it has more (-) electrons than (+) protons
positive
negative

20. Charge of Ions Ion charge: right superscript
Cl-1 a chloride ion with a charge of -1
Na+1 a sodium ion with a charge of +1
O-2 an oxygen ion with a charge of -2
If no right superscript, it’s understood to be zero and therefore a neutral atom

21. Putting it all together
How many protons, neutrons, & electrons in each of the following
23Na+1
Got 2 e-
Lost 1 e-
Got 1 e-
34S-2
19F-1 9 1 16
16 p, 18 n, 18 e
9 p, 10 n, 10 e
11 p, 12 n, 10 e
Lost 2 e-
Lost 2 e-
13N-3
Got 3 e-
25Mg+2
64Zn+2 12 30 7
7 p, 6 n, 10 e
30 p, 34 n, 28 e
12 p, 13 n, 10 e

22. What is an amu?
atomic mass unit
amu  1/12 the mass of the C-12 atom