1. Unit 3 Particles with Internal Structure

2. The Elements
Remember, elements are combined to form molecules the way letters are combined to form words.
Presently there are about 115 known elements.
Only 88 occur naturally, the rest are made in laboratories.
Only 9 elements account for most of the compounds found in the Earth’s crust.

3. Table 3.1

4. All living things are made up, mainly, of oxygen, carbon, hydrogen and nitrogen.

5. Symbols For The Elements
Just as each state has a two-letter abbreviation, each element has a one- or two-letter symbol to make life simple for chemists.
Some elements found in the human body are: As, Cr, Co, Cu, F, I, Mn, Mo, Ni, Se, Si, & V.
Notice the first letter is ALWAYS capitalized and the second letter, if present, is Not capitalized.

6. Symbols For The Elements
Some symbols make sense like O for oxygen and H for hydrogen or Ni for nickel.
Others, like Pb for lead or Fe for iron, don’t automatically make sense; they originated from the Greek or Latin names of plumbum (Pb) and ferrum (Fe).

7. Dalton’s Atomic Theory
Scientists studying matter in the eighteenth century made the following observations:
Most natural materials are mixtures of pure substances.
Pure substances are either elements or combinations of elements called compounds.
A given compound always contains the same proportions (by mass) of the elements.
John Dalton attempted to explain these observations in 1808.

8. Dalton’s Atomic Theory
Elements are made of tiny particles called atoms.
All atoms of a given element are identical.
The atoms of a given element are different from those of any other element.
Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers and types of atoms.
Atoms are indivisible in chemical processes. That is, atoms are not created or destroyed in chemical reactions. A chemical reaction simply changes the way atoms are grouped together.

9. Formulas of Compounds
The types of atoms and the number of each type in each unit (molecule) of a given compound are conveniently expressed by a chemical formula.
The atoms are indicated by their symbols and the number of each type is indicated by a subscript (unless there is only one).
Ex) C6H12O6 or H3PO4

10. Practice
Write the formula for each of the following compounds, listing the elements in the order given:
A molecule contains four phosphorous atoms and ten oxygen atoms.
A molecule contains one uranium atom and six fluorine atoms.
A molecule contains one aluminum atom and three chlorine atoms.

11. What is inside an atom?
Build an Atom Activity

13. Modern Atomic Structure
Every atom is composed of the three basic subatomic particles. (Protons, electrons, neutrons)
Different elements have different numbers of each of these subatomic particles.
The reason one element behaves differently than another lies in the number and arrangement of their electrons.
When atoms get close to each other their electron “clouds” can overlap and interact.

14. Figure 3.9: A nuclear atom viewed in cross section.

15. In any box on the Periodic Table, what information can you find?
Atomic number = number of protons, unique for every element, no 2 elements have the same atomic # 6 C
12.01
Element symbol = can be 1,2 or 3 letters, first letter is always capitalized, and succeeding letters are always lower case
Average Atomic Mass = Protons + Neutrons
the weighted average of all the mass numbers for each isotope of the element

16. Isotopes
Two atoms of the same element (same number of protons) with different numbers of neutrons.
Figure 3.10: Two isotopes of sodium.

17. Isotopes
There are two important numbers associated with any given element:
Atomic Number – The number of protons in a nucleus.
Mass Number – The SUM of the number of protons AND neutrons (a.k.a. nucleons) in a nucleus (NOT the sum of their masses).
We should note that two different isotopes will have the same atomic number, but different mass numbers.

18. Isotopes The two previous examples of isotopes of sodium would be:
The example on the left would contain protons and 12 neutrons (23-11=12).
The example on the right would contain 11 protons and 13 neutrons (24-11=13).

19. Practice Problems
Write the symbol for each of the following atoms, and list the number of protons, neutrons, and electrons for each.
The cesium atom with a mass number of 132.
The iron atom with a mass number of 56.
The krypton atom that has 48 neutrons.
The nitrogen atom that has 6 neutrons.

20. M&M Isotope Lab

21. Weighted Average Atomic Mass
Remember elements can have different isotopes which means that they vary in their number of neutrons.
If you have 3 different isotopes of the same element:
15 atoms have a mass of 21
8 atoms have a mass of 23
2 atoms have a mass of 19
We can calculate the weighted average by multiplying the number of atoms by their mass:
(15) (21) = = 21.48
(8) (23) =
(2) (19) = average atomic mass
537

22. Using % to find Average Atomic Mass
Usually we only know the percents of various isotopes that make up different elements, we can use this to calculate the average atomic mass.
If we have 100% chlorine:
75.77% of mass is 35  .7577x35 = 26.52
24.23% of mass is 37.2423x37= 8.96
Add the 2 together to get the atomic mass:
= 35.48

23. Practice Oxygen has 3 isotopes 16O, 17O, 18O 99.76% of mass is 16O
What is the average atomic mass?
Find the atomic mass if 99.64% of mass is 14N and 0.36% is 15N.

24. A Simple Version of the Periodic Table

25. Periodic Table
When looking at periodic table elements are arranged in horizontal rows by increasing atomic number.
Horizontal rows are called “Periods”. Periods go left to right

26. Periodic Table The vertical columns are called “Groups” or “Families”
Elements in families share similar properties

27. Metals, Semimetals, Non-Metals
All elements on the periodic table are grouped as metals, semimetals or metalloids, or non-metals. Due to the arrangement of the periodic table, it is easy to identify each type of element. Figure 3.12: Elements classified as metals and nonmetals

28. Metals: Fall to left and under the stairs
Properties of Metals:
Efficient conduction of heat and electricity
Malleability
Ductility
A lustrous appearance
Positively charged ions

29. Non-Metals: Right and above the stairs
Dull, Brittle
Negatively charged ions
Nonconductors
-insulators

30. Semimetals or Metalloids: Makeup the stairs
Properties of both metals and non-metals
Semiconductors

31. Lanthanide and Actinide Series
Mostly human made elements
Radioactive elements

32. Group 1A – Alkali Metals

33. Group 2A – Alkaline Earth Metals

34. Group 7A or 17: Halogen Family

35. Group 8A or 18: Noble Gases
Do not react easily with anything, due stable electron configuration
All other elements strive to reach noble gas configuration for maximum stability by reacting with other elements.

36. Transition Metals: Group 3B-12B

37. Who is a solid, liquid or gas?
When we look at the elements on the periodic table, who is a solid, liquid or gas in their natural state?
Most elements are not found in their elemental state, most elements are found in compounds with other elements.
Most elements on the periodic table are solids, so we will point out those who are gas or liquid.

38. Liquids
Only 2 elements in their elemental form are a liquid at 25 degrees Celsius: Mercury and Bromine

39. Gases
More elements exist in their elemental form as a gas, but there are some important distinctions to make about these gases.
The noble gases are a gas, called monatomic gases. The prefix mono- means one. And monatomic gases exist as individual atoms.
Figure 3.13: A collection of argon atoms.

40. Gases
There is another group of gases called diatomic gases. The prefix di- means two. These elements travel in pairs as molecules.
Figure 3.14: Nitrogen gas contains NXN molecules.
Figure 3.14: Oxygen gas contains OXO molecules.

41. Diatomic molecules
There are 7 elements that exist as diatomic molecules, you will simply need to find a way to memorize these.
If you notice, all of the halogens fall in this category, and then hydrogen, nitrogen, and oxygen.

43. What is an ion?
When we discussed atoms before, we were always looking at a neutral atom.
Neutral atoms always have equal numbers of protons and electrons.
protons = +1 charge
electrons = -1 charge
When atoms have unequal numbers of protons and electrons, then the atom is a charged particle called an ion.

44. Ion Facts Ions are atoms, or groups of atoms, with a charge.
The charge is created by different numbers of protons and electrons.
In an atom ONLY electrons can move.
Atoms gain or lose electrons to become ions.

45. Cations and Anions There are 2 types of ions: cations and anions.
Cations are ions with a (+) positive charge. To form a cation, an atom has lost electrons.
Example: Na loses an electron and becomes Na+
Anions are ions with a negative charge. To form an anion, an atom has gained electrons.
Example: Cl gains an electron and becomes Cl-

46. Basic Names for Ions
Cations do not change names from their neutral atoms.
Example: Magnesium loses 2 electrons and becomes Mg2+ which is named magnesium ion.
Anions change the end of their name to –ide.
Example: Chlorine gains an electron and becomes Cl-. We would change the name from chlorine to chloride.

47. Some Common Anion Names
What would the names of the following ions be?
Chlorine =
Fluorine =
Bromine =
Iodine =
Oxygen =
Sulfur =

48. How to Determine the Charge
When determining the charge for an atom we can use the periodic table to help.
The number of valence electrons determines the charge.
All atoms want 8 valence electrons.
If an atom has 1-3 valence electrons the atom will lose them to become positive.
If an atom has 6-8 valence electrons the atom will gain electrons to become negative.
We can determine the charge by looking at the periodic table.

49. Figure 3.19: The ions formed by selected members of groups 1, 2, 3, 6, and 7.

50. Practice Determine the name and charge of the following ions:
Potassium
Bromine
Calcium
Sulfur
Aluminum
Strontium
Cesium