1. 1.1 Nature of Chemistry and 1.2 Atomic Structure

2. Empirical knowledge: based on observable phenomena that is observed directly and is capable of being experimented on.
Theoretical knowledge is created to explain observations based on ideas. It is an attempt to rationalize things we cannot see.

3. Theories are constantly being revised to make them fit the evidence that is being evaluated.
Theories aim to describe, explain, and predict in the most concise manner possible.

4. IUPAC International Union Pure and Applied Chemistry
Established in 1919
Role is to help regulate standards and procedures in chemistry

5. Early Models of Matter

6. Democritus
matter can be divided until you arrive at the smallest piece possible
called it the atom
atoms are in constant motion
empty space between atoms

7. Aristotle thought Democritus was out to lunch!
believed all matter was derived of four substance: earth, water, fire and air
idea lasted for 2000 years

8. John Dalton “pool ball” model
all matter is composed of tiny indivisible spheres called atoms
all atoms of an element have the same properties
atoms of different elements will have different properties
atoms of two or more elements can combine in constant ratios to form new compounds
atoms cannot be created, destroyed or subdivided in a chemical change

9. J. J Thomson “raisin bun” model
first to come up with the idea that an atom consisted of positive and negative parts
negatives were embedded in a positive sphere

10. Hantaro Nagaoka
He proposed a “Saturian or planetary model" of the atom (1904).
The model was based on principles used to explain the stability of Saturn’s rings.
the rings are stable because the planet they orbit is very, very massive.

11. Hantaro Nagaoka -Predictions
a very massive nucleus (analogous to a massive planet)
electrons revolved around the nucleus, bound by electrostatic forces (analogous to the rings revolving around Saturn, being bound by gravitational forces)

12. Ernest Rutherford “beehive” model gold foil experiment
proved that the positive part of an atom was at the centre
there was a lot of empty space in an atom
that some electrons could be found amongst the empty space

14. James Chadwick proved the existence of neutrons
neutrons are heavy particles with no charge

15. Neils Bohr (1885- 1962) Danish Physicist

16. Bohr’s Model Based on the element Hydrogen
electrons orbit the nucleus at discrete energy levels
these energy levels are at a fixed distance from the nucleus
the electron travels along a three dimensional path called an orbit

17. these energy shells are designated by the principal quantum number n
electrons can transition between levels
in order to jump it must receive that specific amount of energy that would put it to the next energy level

18. when an electron loses its gained energy, it falls back to its original orbit “ground state”

19. Assumptions
an electron can travel indefinitely within an energy level without losing energy
that the greater the distance between the nucleus of the atom and the energy level, the greater the energy required for an electron to travel in that energy level
that an electron cannot exist between orbits, but can move to a higher unfilled orbit if it absorbs a specific quantity of energy and to a lower unfilled orbit if it loses energy

20. Experimental Evidence
The basis for Bohr’s Theory came from observing line spectra
line spectrum: a pattern of distinct lines, each of which corresponds to light of a single wavelength, produced when light consisting of only a few distinct wavelengths passes through a prism or spectroscope

21. How spectroscopy works!

22. This is the bright line spectrum for hydrogen

23. Particle Location Charge Mass Symbol
Electron
Orbiting the nucleus
Negative
9.11 × kilograms e-
Proton
Nucleus
Positive
1.67 × kilograms p+
Neutron
Neutral n0

24. Atomic Number and Mass Number

25. What is an atom's atomic number (Z)?
number of protons in the nucleus
each element has a unique number that identifies the number of protons
Oxygen atoms contain 8 protons and has an atomic number of 8

26. What is an atom’s mass number (A)?
derived from the number of protons and neutrons in an atoms nucleus.
(N) = A- Z

27. The Mass of an Atom
The mass of an atom is very small. Scientists compare the mass of an atom to that of a standard atom.
As the mass of an atom is compared to that of another reference atom it is referred to as a relative atomic mass (Ar).
The reference atom used to compare all other atomic masses is the stable and abundant isotope of carbon carbon-12.

28. The C-12 atom is said to be 12 unified atomic mass units (u)
The C-12 atom is said to be 12 unified atomic mass units (u). Consequently, one atomic mass unit is equivalent to the mass of a nucleon (proton or neutron).
Therefore, the atomic mass unit is defined as 1/12 the mass of a carbon-12 atom