1. How We Know What We Can’t See Looks Like Day 2
Atom’s Story
How We Know What We Can’t See Looks Like
Day 2

2. A. Tom on a Band

3. Name Symbol Mass Protons p 1 Neutrons n 1 Electrons e-- 1/2000
Two atoms were walking down the road. One turns to the other and says, “I think I’ve lost an electron.” “Are you sure?” asks his companion. “I’m positive”, he replied.
Name Symbol Mass
Protons p 1
Neutrons n 1
Electrons e-- 1/2000
(actually 1/1840)

4. Atomic Particles Particle Charge Mass # Location Electron -1
Electron cloud
Proton +1 1
Nucleus
Neutron

5. The Atomic Scale
Most of the mass of the atom is in the nucleus (protons and neutrons)
Electrons are found outside of the nucleus (the electron cloud)
Most of the volume of the atom is empty space
“q” is a particle called a “quark”

6. About Quarks… Protons and neutrons are NOT fundamental particles.
Protons are made of two “up” quarks and one “down” quark.
Neutrons are made of one “up” quark and two “down” quarks.
Quarks are held together
by “gluons”

7. Atomic Number (Z) identifies the number of protons
identifies the element.
Element
# of protons
Atomic # (Z)
Carbon
Phosphorus
Gold 6 6 15 15 79 79

8. Mass Number Nuclide p+ n0 e- Mass # the number of protons and neutrons
NOT the same as average atomic mass
NOT on the PT
Mass of the nucleus of an isotope.
Written with name in hyphen notation ex. Carbon – 12
Mass # = p+ + n0
Nuclide p+ n0 e-
Mass #
Oxygen - 10 - 33 42
- 31 15 18 8 8 18
Arsenic 75 33 75
Phosphorus 16 15 31

9. Nuclear Symbols Mass number (p+ + no) Element symbol Charge (p+ - e-)2+
Charge
(p+ - e-)
Atomic number
(number of p+)

10. Isotopes atoms of the same element having different masses
varying numbers of neutrons.
Isotope
Protons
Electrons
Neutrons
Nucleus
Hydrogen–1
(protium) 1
Hydrogen-2
(deuterium)
Hydrogen-3
(tritium) 2

11. Composition of the nucleus
Atomic Masses
Atomic mass is the average of all the naturally isotopes of that element.
Carbon =
Isotope
Symbol
Composition of the nucleus
% in nature
Carbon-12
12C
6 protons
6 neutrons
98.89%
Carbon-13
13C
7 neutrons
1.11%
Carbon-14
14C
8 neutrons
<0.01%

12. But now we know. . . Let’s learn about ISOTOPES! Can you say: PROTON?
NEUTRON?
ELECTRON?
QUARK?
But now we know. . .
1. Matter is made of very small particles called “atoms”
2. Atoms cannot be divided, created, or destroyed.
Atoms of one kind of element are identical to other atoms of that same element. Atoms of different elements are unlike.
Let’s learn about
ISOTOPES!
4. Atoms somehow combine in small, whole-number ratios to form chemical compounds.
In chemical reactions, atoms are somehow combined, separated, or rearranged.

13. Isotopes of Hydrogen Protium H Deuterium H Tritium H1
Protium H 2 3
Deuterium H
Tritium H 1 1 1
Deuterium and tritium reveal on click
1 proton 1 neutron
Mass = 2
1 proton 2 neutron
Mass = 3
1 proton
Mass = 1

14. Relative masses on the P. Table are weighted averages of the isotopes.
Atoms of the same element (they have the same number of protons) that have different masses because they have different numbers of neutrons. C C 13 C 14 C 11 12
Carbon – 12 makes up the greatest % of carbon in the universe
MASS # 12 C 6
ATOMIC #
Relative masses on the P. Table are weighted averages of the isotopes.

15. Subatomic Particles 3 main subatomic particles Nucleus Proton Neutron
Electron
Nucleus
Center of atom
times smaller than atom
99.9% of atom’s mass
Contains 2 subatomic particles
Protons
neutrons

16. Parts of the atom 24 28 22 Ion +2 32S2- 32.07 16 32 16 16 18 Ion 56
Name
Symbol
Atomic
Mass
Number
Mass number
# of protons
# of neutrons
# of electrons
ion/ isotope
Charge
11B
10.81 5 11 6
52Cr+2
52.00 52 24
Sulfur – 32 -2
100Ru
101.1 44 4
Titanium-44
47.87 22 +2
32Si
40Ca
40.08
Neither
Ytterbium-140 70
Neither
Boron – 11
Chromium-52 24 28 22
Ion +2
32S2-
32.07 16 32 16 16 18
Ion 56
Ruthenium-100
100
Isotope
44Ti2+ 22 20
Ion/ isotope 14 18 14
Isotope
Silicon-32
28.09 14 32
Calcium-40 20 40 20 20 20
140Yb
173.0
140
Isotope