1  

The  Gold  Foil  Experiment                

 Most of the particles passed through, some are deflected.

 

ATOMIC STRUCTURE Reference Table: Periodic Table, Table O 1. Models of the atom:

A. Dalton: tiny, indestructible particles with no internal structure.

B. J.J. Thomson: plum pudding model electrons embedded in a positive atom.

C. Rutherford Model of the atom: most of the atom is empty space with small, dense positively charged nucleus.

D. Bohr’s model of the atom stated that the electrons traveled in certain orbits.

E. The Quantum Mechanical Model:

2. Structure of the atom: PEN

• Proton: positive charged; 1 amu • Neutron: neutral; 1 am • Electron: negative charged; 1/1836 amu

3. The charge of the atom is neutral. The nucleus is

positive. 4. Nucleon: particles found in the nucleus (protons and

neutrons) 5. Nucleus: contains most of the mass of the atom, has a

positive charge. The number of protons is called the nuclear charge.

6. 1 amu: the atomic mass unit; base on 1/12 the mass of a

carbon 12 atom. 7. Atomic number: the number of protons in an atom; used

to identify the element. 23 Atomic number à 11 Na 8. Mass number: See the periodic table. Mass number à 23 11 Na 9. Number of neutrons= mass number – atomic number mass number 23 atomic number - 11 Na 12 10. The Ground state: the lowest and most stable, energy

state of an atom. See periodic table 7 3 Li 2-1 11. Excited state: Absorption of energy will cause electrons

to temporarily jump to higher energy levels and when the electrons fall back down to lower levels they emit energy in the form of light.

7

3 Li 1-2

Present: the Quantum Mechanical Model  

Bohr 1913

Rutherford 1909

J.J. Thomson 1897

 msm  

Dalton 1803

α  

_-­‐=_  

   

2  

           Na        2-­‐8-­‐1  

12. How does an electron become excited?

13. Isotopes: same element, same atomic number, but

different number of neutrons and mass number. Mass Number 16 17 18

atomic number - 8 O - 8 O - 8 O neutrons 8 9 10 99.76% 0.04 % 0.20 % the number of neutrons = mass number – atomic number 14. Atomic mass: the average of the atomic mass of the

naturally occurring isotopes.

Isotope % Abundance Mass (amu) Boron-10 19.78 10.013 Boron-11 80.22 11.009

Atomic mass = (19.78 X 10.013) + (80.22 x 11.009)

100 100

Atomic mass = 1.9805 + 8.831 Atomic mass= 10.81 a.m.u.

15. Valence electron:

• electrons in the outermost shell 16. Lewis Electron Dot: represent the valence electron. Na ● 17. Draw the electron configuration of Na: 2-8-1

18. Spectroscope: An instrument that breaks light into colored bands

19. The visible spectrum is that part of the electromagnetic

spectrum that is visible to the eye, generally with wavelengths ranging between about 400 and 700 nm.

20. The Electromagnetic Spectrum:

21. Type of Spectra:

a) Continuous Spectrum: Separation of light by a

prism according to wavelength

Valence  electron:  1  

Kernel:  nucleus  +    2-­‐8  

   

3  

b) Bright-Line Spectra or Fingerprints of Elements: Each element has its own distinct line spectra made up of only the lines of specific wavelength that correspond to its atomic structure.

21. Examine the spectra below. The bottom spectrum is a mixture of two or more of the

elements above it. Which elements are present in the mixture?

Answer: ____________________________________

23. Flame Test:

Every element absorbs and emits different amounts of energy

Lithium Calcium