5. Chapter 2 – Matter & Change
By Kendon Smith – Columbia Central HS – Brooklyn, MI
6.
7. Formulae
H2O is the formula of water
H2 O
O
H
2 hydrogen atoms
1 oxygen atom
CaO, CaSO4, Ca(OH)2, NH4NO3, CO2, NH3
Diatomic molecules
Ionic bonds
H
8. Formulae
H2O is the formula of water
H2 O
O
H
2 hydrogen atoms
1 oxygen atom
CaO, CaSO4, Ca(OH)2, NH4NO3, CO2, NH3
Diatomic molecules
Ionic bonds
H
9. Formulae
H2O is the formula of water
H2 O
O
H
2 hydrogen atoms
1 oxygen atom
CaO, CaSO4, Ca(OH)2, NH4NO3, CO2, NH3
Diatomic molecules
Ionic bonds
H
11. 1. Condensation
Prior
to condensation:
*
particles slow down
*
not far apart
*
less violent collisions
Phase
change follows:
*
Spaces decrease
*
Forces increase
*
more orderly arrangement
12. 2. Solidification
Prior
to solidification:
*
particles move very slowly
*
particles very close to each other
*
only vibrates
Phase
*
*
change follows:
very small spaces between particles
forces between particles become
very strong
13. 3. Melting
Prior
to melting:
*
particles move fast
*
particles further apart
Phase
change follows:
*
spaces increase
*
forces decrease
*
less orderly arrangement
14. 4. Evaporation
Prior
to evaporation
*
particles move very fast
*
particles very far apart
*
violent collisions due to high speed
Phase
change follows:
*
spaces between particles are big
*
forces negligible
*
disorderly arrangement
19. Assumptions
1. The positive charges are all together in a small
volume in the nucleus.
2. The nucleus is surrounded by a space that contains
the e- (v. Small mass) – e- are responsible for the
great volume of an atom.
3. Mass is concentrated in the nucleus.
Later investigations predicted that the nucleus is
positively charged. # Protons = # electrons. e don’t move like bees around a hive, e- would
collapse
into nucleus.
20. Planetary atomic model
e- move in energy levels
e- with same E values,
move in same E levels
Valence orbitals have
higher energy than those
close to the nucleus
Energy levels closer to
the nucleus are filled first
with eEach energy level can
only take a specific
amount of ee- in orbits close to the
•When e- absorb energy it
rises in energy level.
•This (excited) state is
unstable and e- fall back
to lower energy levels
21. Wave mechanical atomic model
Bohr’s atomic model explains the structure of
hydrogen, but not those of atoms with more than
one electron.
The discovery of wave properties of electrons
gave us a more acceptable model.
e- have both particle and wave properties.
Schrodinger stated that moving e- form a 3D wave
space that surrounds the nucleus, called an
orbital.
22. Neutron
J. Chadwick discovered a particle with a mass
nearly equal to the proton.
Neutral charges, called neutrons.
23. Atomic mass and diameter
Atoms are extremely small with small masses.
ELEMENT
Hydrogen
1,673 55 X 10 -27
Carbon
1,994 36 X 10 -26
Oxygen
2,656 59 X 10 -26
Uranium
AVG ATOMIC MASS
3,952 33 X 10 -25
Diameters are also extremely small.
Most of the volume of an atom is empty space, the
nucleus accounts for most of the mass of an atom at
the centre.
24. Relative atomic mass
Hydrogen
is the lightest atom and is
chosen as the standard for an atomic
mass scale.
This mass is equal to 1.
Using proportion to find the atomic
masses of other elements relative to a
mass of 1.
1,673
55 X 10 -27 kg of Hydrogen = 1
25. Structure of the atom
The
atom consists of very
many small subatomic
particles.
In chemistry we work with
protons, neutrons and
electrons.
Protons and neutrons are in
27. Isotopes
Carbon (atomic # 6) has three natural isotopes
with atomic weights of 12, 13 and 14.
isotope
======
C-12
C-13
C-14
#p
==
6
6
6
#n
==
6
7
8
Tin (Sn, atomic # 50) has ten natural isotopes with
atomic masses of 112, 114, 115, 116, 117, 118, 119,
120, 122 and 124. How many protons and neutrons
do these isotopes have?
