1. CHEMISTRY

2. Atoms, Elements & the Periodic Table
Describe the structure & parts of an atom.
Identify the properties of an atom.
Interpret information on a periodic table to understand how elements are grouped.

3. What are the elements made of?
Element-the simplest pure substance.
Elements are made of atoms, and each element’s atoms are unique to that element
Atoms-the basic building blocks of all matter. They are the smallest particles into which an element can be divided and still be the same substance.
Atoms are made of 3 types of particles-protons, neutrons and electrons

4. The History of Atomic Theory

5. Democritus – 440 BCE Greek Philosopher 2445 years ago.
Called particles that made up “stuff” ATOMS
Atomos (Greek word)
“not able to be divided”(uncuttable)
small hard particles
Constantly move

6. Dalton - 1803 Atoms make up all substances (the elements)
Atoms can not be created, divided or destroyed.
Atoms combine to make other substances.
Conducted experiments

8. Dimitri Mendeleev Proposed the laws of the periodic table
1869-developed the first periodic table
Table was arranged according to increasing atomic weight
Left spaces for elements yet to be discovered

9. J.J. Thomson
Discovered negatively charged particles in atoms called Electrons.
Conducted Cathode Ray Tube experiment
Led to the Plum Pudding Model

11. Ernest Rutherford - 1909 Discovered the nucleus Nucleus
Small tiny very dense center of atoms
Where most the atoms mass is located
Atoms are mostly empty space where electrons are found
Conducted the Gold Foil experiment

13. Niels Bohr
Electrons move around the nucleus of atoms in definite paths.
Electrons jump between levels from path to path.
Bohr’s model

15. Most Recent Atomic Theory
Schrodinger and Heisenberg
Electron paths cannot be predicted.
Electrons are likely to be found in regions around the nucleus called electron clouds.
Called the electron cloud model.

16. Recent Discoveries Chadwick
1932-Discovered that neutrons exist in the nucleus of atoms
Neutrons have no charge and the mass equal to protons and help to stabilize the atom
Gell-Mann
1969-Subatomic particles are made of smaller particles called quarks

18. PERIODIC TABLE =ORGANIZED ELEMENTS
Elements are:
PURE-Made of like atoms of that element
Identified by it’s atomic number (# of protons)
Arrangement of electrons determines the elements properties (such as conductivity and reactivity).

19. The Element Song Link to video
Select broadband player.

20. The Structure of an Atom
Protons – POSITIVE charged particles inside the nucleus (center).
Neutrons – neutral particles inside the nucleus that have NO CHARGE!
Electrons – NEGATIVE CHARGED particles in atoms found around the nucleus.

21. Atomic Particles Location Charge Mass Protons Nucleus + positive
Heaviest particle
Neutrons
O Neutral
Similar to a proton but carry no charge
Electrons
Orbiting outside the nucleus in electron clouds
- Negative
Lightest particle
Smallest part of an atom

22. Outside the nucleus
Can be called a electron cloud, shell, energy level, orbit or ring
Area outside the nucleus where electrons are found
1st cloud=2 electrons
2nd cloud=8 electrons
3rd cloud=18 electrons

23. Boron (B)
Atomic #=5
Atomic Mass=11
Protons=5
Neutrons=6
Electrons=5

24. Sodium-(Na)
Atomic #=11
Atomic Mass=23
Protons=11
Neutrons=12
Electrons=11

26. Energy Levels - Electron Clouds
Regions around the nucleus where electrons are arranged.
Electrons further away from the nucleus have more and more energy.
Each level or cloud can hold a specific # of electrons.
1st level - 2 electrons
2nd level - up to 8 electrons
3rd level-up to 18 electrons

27. Valence Electrons
The electrons in the outermost energy level (electron cloud).
Very important because they determine how an element will react with other substances

28. What’s in the Box?

29. Atomic Number 5 B
10.81
Boron
Equals the number of protons inside the nucleus of the atom.
Atomic Number=Number of Protons=the number of electrons
Determines the element.
All atoms of an element have the same atomic number.
No two elements have the same atomic number.

30. Symbol B All elements have their own unique symbol5 B
10.81
Boron
All elements have their own unique symbol
Symbols can be one or two letters
The first letter is always a capital letter
The second is always a lower case letter
Symbols don’t always match their English word bc most are from Latin or Greek roots.
Example: Fe=Iron (English) Ferrum (Latin)

31. Mass Number 5 B
10.81
Boron
The total number of protons and neutrons in an atoms nucleus.
Number under the element symbol
Protons + Neutrons = Mass Number
Practice: If an atom has 12 protons, 14 neutrons and 12 electrons, what is its mass number?
Practice online
Ans: 12 protons + 12 neutrons=24

32. Atomic Mass Unit - amu
Unit of measurement for the mass of subatomic particles.
1 amu = 1.7 X They are TEENY TINY!!!
grams
Proton = 1 amu
Neutrons = 1 amu
Electrons = almost zero (TINIEST particle with the least mass)
Most of the mass is in the nucleus with protons and neutrons
Otherwise atoms are mostly EMPTY SPACE
Amu will be addressed in slide 14, but you can refer back to this slide for review at the end

33. Atomic Mass Refers to the weight of the atom.
Atomic Mass= Protons + Neutrons
Never negative
Mass

34. The Charge of an atom To find the charge of an atom-
Find the number of protons (+)
Find the number of electrons (-)
Represent the electrons as a negative number
Add the protons and electrons to find the charge
Ex: Calcium atom has 12 protons and 10 electrons. What is the charge of this atom?
Answer 12 proton + 10 electrons
(-10)= +2
This atom would be positive (+)
Be sure to reinforce that these are not neutral atoms. When students look at their periodic table, they can assume all of the elements’ atoms are neutral unless given additional information. Also point out that the only thing to change the charge is whether the atom has gained or lost electrons, and that the # of protons will always stay the same. The method above is designed to help students avoid thinking “the atom LOST electrons, so it must be negative, “ and lets them use simple math

35. More practice with charge
What is the charge of a copper atom with 26 electrons?
What is the charge of a Sulfur atom with 18 electrons?
29 protons (+) + 26 electrons (-) 29-26=+3 positive
Copper’s atomic # is 29 if students do not have their periodic table
16 protons (+) + 18 electrons (-)
16-18=-2
negative

36. Review Nucleus-contains protons and neutrons
Electron Cloud-electrons orbit the nucleus
Elements are made of
Atoms, which contain
Protons (+), neutrons (o)and electrons (-)
#protons
# neutrons
Mass #

37. Periodic Table Overview

38. How the Elements are Arranged
Groups/Families:
Similar properties
Periods/Rows:
Increasing atomic number/mass

39. Groups/Families
Columns of the periodic table that consist of elements that have the same number of valence electrons.
Groups 1 and 2 - same # as group
Groups the group #
Groups no general rule.

40. Periods
Rows of the periodic table that consist of elements with the same number of electron clouds or energy levels.

41. Alkali Metals
Group #1
All metals
1 Valence Electron
Very reactive

42. Alkaline-Earth Metals
Group #2
All Metals
2 Valence Electrons
Very reactive but less than group #1.

43. Transition Metals Groups # 3-12 All metals 1-2 valence electrons
Less reactive than group #2
Also contain lanthanide and actinide series (radioactive/unstable).

44. Groups # 13-16
Elements change from metals to nonmetals and include the metalloids.
Atoms have 10 fewer valence electrons than the group #.
Boron Group # valence electrons
Carbon Group # valence electrons
Nitrogen Group # valence electrons
Oxygen Group # valence electrons

45. Halogens Group 17 All nonmetals 7 valence electrons Very reactive
Only need to gain 1 more electron.

46. Noble Gases Group # 18 All nonmetals
8 valence electrons - except helium only has 2.
Unreactive
Have a full outer electron cloud (energy level).

47. Hydrogen stands alone 1 valence electron Very reactive
Reacts violently with Oxygen under the right conditions.

48. Everyday Uses

49. Isotopes
Atoms of elements that have the same number of protons (atomic number) but a different number of neutrons inside the nucleus.

50. Ions Charged particles that form during chemical changes.
Form when one or more valence electrons are transferred from one atom to another.

51. Ions are Charged! + or -
Atoms that lose electrons become positive ions.
Atoms that gain electrons become negative ions.
Cl gains an electron from Na to form NaCl -
Cl ion is negative - more electrons (-)
Na ion is positive - more protons (+).