1. Chapter 11 Introduction to Atoms

2. An atom is the smallest particle into which an element can be divided and still be the same substance.
See timeline handout for the development of the model of the atom.
Identify atom models of Thomson, Rutherford, Bohr, and the Modern Model.

3. What do I need to know? Know the scientist
their contribution to the developing model of an atom (their experiment)
their atom model!

4. Structure of the atom
The atom contains a nucleus surrounded by one or more electrons
The nucleus contains protons and neutrons.
Draw an atom here
(Page 320)

5. Structure of the atom
nucleus
energy
level

6. Particle
Charge
Location

7. Particle
Charge
Location
Proton

8. Particle
Charge
Location
Proton
Positive
(+)

9. Particle
Charge
Location
Proton
Positive
(+)
Inside nucleus

10. Particle
Charge
Location
Proton
Positive
(+)
Inside nucleus
Neutron

11. Particle
Charge
Location
Proton
Positive
(+)
Inside nucleus
Neutron
Neutral

12. Particle
Charge
Location
Proton
Positive
(+)
Inside nucleus
Neutron
Neutral

13. Particle
Charge
Location
Proton
Positive
(+)
Inside nucleus
Neutron
Neutral
Electron

14. Particle
Charge
Location
Proton
Positive
(+)
Inside nucleus
Neutron
Neutral
Electron
Negative
(-)

15. Particle
Charge
Location
Proton
Positive
(+)
Inside nucleus
Neutron
Neutral
Electron
Negative
(-)
Outside nucleus

16. Terms to copy in notes:
atomic number – the number of protons in the nucleus of an atom.
(*The number of protons identifies an element!)
atomic mass – the average mass of one atom of an element.
atomic mass unit (amu) – a measurement of the mass of one proton or one neutron.

17. Chemical Symbols Hydrogen symbol is H Cobalt symbol is Co
A chemical symbol is one or two letter(s) representing an element.
If the symbol is one letter, it is a printed capital.
Hydrogen symbol is H
If two letters, the first is a printed capital and second is lower case.
Cobalt symbol is Co

18. Know the Following Elements!
The first 20 elements and symbols, plus 7 others, must be properly identified together.
iron copper
silver gold
mercury tin lead
The symbols must be written in correct form.
Spelling counts!

19. Electrons
Electrons are located in an electron cloud around the nucleus.
There are different energy levels (“orbits” in the Bohr model) that electrons fill.
1st energy level can hold 2 electrons
2nd can hold 8 electrons
3rd can hold 18 electrons
4th can hold 32 electrons

20. Energy Levels of carbon atom

21. Fe Today’s periodic table is based on atomic number.
Each element’s square contains:
atomic number (protons)
chemical symbol
element name
atomic mass (protons &
neutrons)
This is an average 26 Fe
Iron
55.847

22. How to find the number of neutrons in an atom
Round the atomic mass to the nearest whole number.
Subtract the number of protons (atomic number).
The difference is the number of neutrons.
boron atomic mass (protons + neutrons)
rounded
atomic number (protons)
6 neutrons

23. Aluminum
atomic mass
rounded
- atomic number
neutrons

24. Practice calculating the number of neutrons in an atom
Number a blank sheet of paper 1 to 10.
Write the name for each element from the periodic table for elements 1-10.
Use the right side of your paper to calculate the number of neutrons for elements 1-10.
Write your answer next to the elements name.

25. Gaining or losing a neutron makes an atom an isotope.
Isotopes are still the same element, just more or less neutrons.
carbon 12
has 6 neutrons (always 6 protons)
carbon 14
has 8 neutrons (always 6 protons)
The 12 refers to
the mass number
(protons + neutrons)

26. Valence electrons are electrons farthest away
Valence electrons are electrons farthest away from the nucleus (outer energy level).
- involved with chemical reactions.
- gives an atom its chemical characteristics.
- can be shared, or transferred.
- Atoms with a full valence energy level are most stable (less reactive).

27. hydrogen oxygen carbon neon
electron dot diagram – represents the valence electrons of an element.
- uses an element symbol surrounded by dots representing valence electrons.
H O C Ne
hydrogen oxygen carbon neon

28. The Periodic Table of Elements
Chapter 12 Notes
The Periodic Table of Elements
In 1869 a Russian scientist Dmitri Mendeleev arranged elements in order of increasing atomic mass, and chemical properties.
He used his table to predict properties of elements not yet discovered!

29. Fe Today’s periodic table is based on atomic number!
Each element’s square contains:
atomic number (protons)
chemical symbol
element name
atomic mass (protons &
neutrons)
This is an average 26 Fe
Iron
55.847

30. An element’s properties can be predicted by its location on the periodic table.
Groups or families:
vertical columns numbered 1-18.
elements have similar properties
Periods:
across rows numbered 1-7
elements have predictably different patterns.

31. Metals Metals are found to the left of the stair step.
Physical properties:
Hardness
Shininess (luster)
Malleability (pound into shapes)
Ductility (drawn out into a wire)
Good conductors
Magnetic (Co, Ni, Fe)
Mostly solids at room temp.

32. Metals Chemical properties: wide range
Some violently react with water (Na, K)
Some unreactive (Au, Cr)
Some corrode (react slowly with O2 and flake off)
Alloys (mixture of metals)
bronze (Cu + Sn)
stainless steel

33. Metals
Elements are increasingly nonmetallic reading left to right.
Tend to lose electrons forming
positive ions (1+, 2+)
Alkali Metals
Group 1 (1 valence electron)
Most reactive metals!
Very soft & shiny

34. Metals Alkaline Earth Metals Group 2 (2 valence electrons)
Not as reactive as Group 1 but more reactive than most metals.
Fairly hard, grey-white color
Good conductors of electricity

35. Metals Transition Metals Groups 3-12
Fairly stable, react slowly with H2O
Similar reactivity between columns
Hard and shiny
Good conductors of electricity

36. Metals Lanthanides and Actinides Called rare earth metals
Fit in Periods 6 and 7 between alkaline earth metals and the transition metals.
Placed below periodic table for convenience.
Soft, malleable, shiny, very conductive

37. Nonmetals Located right of the stair step Physical properties:
Most are gases at room temp. (low boiling point).
dull
brittle
lower densities
poor conductors of heat & electricity

38. Nonmetals Halogen Family Chemical properties:
Most readily form compounds
Will take electrons from metals forming
negative ions (1-, 2-)
Will also share electrons
Many form diatomic molecules (O2, N2, H2)
Halogen Family
Group 17 (7 valence electrons)
Very reactive!
Dangerous to humans

39. Nonmetals Noble Gases Hydrogen Group 18 Chemically stable (unreactive)
Do not gain, lose, or share valence electrons
Hydrogen
Alone in upper left corner
Simplest element
Not grouped in a family

40. Metalloids Along the stair step (7 elements)
Have some properties of metals & nonmetals
Used to make semiconductors