1. Chapter 3 – Elements and the Periodic Table
3.1 Introduction to Atoms

2. Atomic Theories
There are about 100 different elements that make up the majority of things around us.
Atom: tiny particles that make up matter
Element: made up of one type of atom
Molecule: made up of more than one type of atom
Hydrogen is the most common element in the universe, making up about 90%.

3. Dalton’s Theory
John Dalton: each element is made up of its own type of atoms.
All of the atoms in one element are identical to one another, but different than any other type of element’s atoms.

4. Thomson’s Model
Atoms contain negatively charged particles called electrons.
Since they do not have an electrical charge, he said there must also be positive particles.

5. Rutherford’s Model
Aimed beams of positive charged particles at gold to see how what resulted.
Most passed right through, leading him to believe that the atom is mostly empty space with a positive charge at its center.
Protons are inside of the nucleus.

6. Bohr’s Model / Cloud Model
Bohr’s: Electrons are found in specific orbits around the nucleus like tree rings.
Cloud: move in a cloud region in energy levels; electrons with different energy levels are in different areas in the cloud.

7. Modern Model of the Atom
Neutrons also exist in an atom; protons and neutrons fill the nucleus, while electrons are in the cloud.
Protons and neutrons are about the same size and mass; electrons are much lighter than them.

8. Atomic Number
Atomic number: the number of protons inside the nucleus of an atom.
This is how elements are arranged on the periodic table.

9. Isotopes and Mass Number
When the number of neutrons changes in an atom, it creates an isotope: atoms of the same element with different neutron numbers.
You can find the number of neutrons in an isotope by subtracting the atomic number from the atomic mass number.

10. Isotopes and Mass Number
Atomic mass number: total number of protons and neutrons in the nucleus
All atoms of a certain element will always have the same number of protons; they may not have the same number of neutrons – changing the atomic mass number.

11. Isotopes and Mass Number
Chlorine:
All chlorine atoms have 17 protons.
If chlorine-37 is an isotope, take 37 (atomic mass) and subtract 17 (atomic number) to figure out how many neutrons the isotope has.
In this case, chlorine-37 has 20 neutrons.

12. Chapter 3 – Elements and the Periodic Table
3.2 Organizing the Elements

13. Mendeleev
Atomic mass: the average mass of all of the element’s isotopes.
Mendeleev, Dmitri: scientist who proposed the first periodic table of elements; organized them based on similar physical and chemical properties, as well as their mass numbers.

14. Modern Periodic Table of Elements
Arranged by similar properties in columns, not rows.
Arranged by atomic number, not atomic mass.
Each element has a square, showing its atomic number, atomic mass, name, and chemical symbol.

15. Modern Periodic Table of Elements
The letters of the symbol represent the physical state of the element at room temp.
White = gas
Blue = liquid
Black = solid
The background color represents whether it is a metal, nonmetal, or metalloid.
Yellow = metal
Purple = metalloid
Green = nonmetal

16. Groups and Periods
The elements in the same column form a group: these share similar physical and chemical properties; named by the number at the top of the column.
Also called a family.
The horizontal rows form periods: properties change from one end of the row to the other end.

17. Trends Ions: Size: Density:
Atoms on the left side form positive ions easily; group 1 loses one electron, group 2 loses 2 electrons.
Group 18 normally don’t form ions at all.
Group 17 usually gains an electron, group 16 usually gains two.
Size:
As you move from left to right, atoms get smaller.
As you move from top to bottom, atoms get larger.
Density:
Atoms at the top of a group are less dense; atoms at the ends of the periods (left and right sides) are less dense than those toward the middle.

18. Chapter 3 – Elements and the Periodic Table
Metals, Nonmetals, and Metalloids

19. Regions on the Periodic Table
Metals are mostly found on the left
Nonmetals are mostly found on the right, with the exception of hydrogen
Metalloids are found in between them

20. Most elements are Metals.
Metals: conduct electricity and heat well, have a shiny appearance, are malleable (easy to shape), are mostly metals at room temp, except mercury.
Examples: sodium (Na), copper (Cu), aluminum (Al)

21. Reactive Metals
Alkali Metals can be found in group 1; they are very reactive.
React rapidly with oxygen and water vapor
Ions of these, like Na+ and K+, are important for life.
Alkaline Earth Metals can be found in group 2; not as reactive as group 1, but more reactive than most metals.
Calcium ions make up our bones and teeth.
Magnesium is very light and used for building.

22. Transition Metals Elements in groups 3-12 are transition metals.
Less reactive than most other metals; gold, silver, iron, and copper.
Important for industry and modern technology.
Two or more metals may be combined to form an alloy: usually stronger, less likely to corrode, or easier to shape.
Brass = copper + zinc

23. Rare Earth Elements
These are the elements shown in the top row of the two separated rows on the periodic table.
Called lanthanides
Harder to isolate in pure form

24. Nonmetals Nonmetals: opposite of metals
tend to be gases at room temp, except for Bromine (l)
Poor conductors or heat/electricity
Nitrogen (unreactive), oxygen (very reactive – burning and rusting), and carbon (all livings things) are common nonmetals.

25. Halogens Group 17 “forming salts”
Very reactive – used to kill harmful microorganisms
Chlorine and iodine

26. Noble Gases Group 18 Almost never react
Argon = about 1% of atmosphere; the rest are even less commonly found.
Used in colorful lights (example – open signs).

27. Metalloids Have properties of both metals and nonmetals
They are along the zigzag line on the periodic table.
Most common = silicon
Used as semiconductors : allow electric charge to pass through sometimes, but prevents things like short circuits and blown fuses.

28. The Periodic Table of Elements
Names, Symbols, Atomic Number, and Electron Configurations

29. Element 1
Hydrogen (H)
Nonmetal
Gas
Atomic Mass ~ 1

30. Element 2
Helium (He)
Nonmetal
Gas
Atomic Mass ~ 4

31. Element 3
Lithium (Li)
Metal (Alkali)
Solid
Atomic Mass ~ 7

32. Element 4
Beryllium (Be)
Metal (Alkaline)
Solid
Atomic Mass ~ 9

33. Element 5
Boron (B)
Metalloid
Solid
Atomic Mass ~ 11

34. Element 6
Carbon (C)
Nonmetal
Solid
Atomic Mass ~ 12

35. Element 7
Nitrogen (N)
Nonmetal
Gas
Atomic Mass ~ 14

36. Element 8
Oxygen (O)
Nonmetal
Gas
Atomic Mass ~ 16

37. Element 9
Fluorine (F)
Nonmetal
Gas (Halogen)
Atomic Mass ~ 19

38. Element 10
Neon (Ne)
Nonmetal
Gas (Noble Gas)
Atomic Mass ~ 20

39. Element 11
Sodium (Na)
Metal (alkali)
Solid
Atomic Mass ~ 23

40. Element 12
Magnesium (Mg)
Metal (alkaline)
Solid
Atomic Mass ~ 24

41. Element 13
Aluminum (Al)
Metal
Solid
Atomic Mass ~ 27

42. Element 14
Silicon (Si)
Metalloid
Solid
Atomic Mass ~ 28

43. Element 15
Phosphorous (P)
Nonmetal
Solid
Atomic Mass ~ 31

44. Element 16
Sulfur (S)
Nonmetal
Solid
Atomic Mass ~ 32

45. Element 17
Chlorine (Cl)
Nonmetal
Gas (Halogen)
Atomic Mass ~ 35.5

46. Element 18
Argon (Ar)
Nonmetal
Gas (Noble gas)
Atomic Mass ~ 40

47. Element 19
Potassium (K)
Metal (alkali)
Solid
Atomic Mass ~ 39

48. Element 20
Calcium (Ca)
Metal (alkaline)
Solid
Atomic Mass ~ 40