1. Chapter 3 Elements and the Periodic Table

2. Structure of an Atom Protons and neutrons have about equal mass
Nucleus: small center core of an atom.
Protons: positively charged atom
Neutrons: particles with no charge + +
e - +
Protons and neutrons have about equal mass
Together the protons and neutrons make up most of the atoms mass.
Nucleus

3. Electrons: negatively charged
particles that move rapidly around
the nucleus
Electron cloud: the space around the nucleus
where the electrons are located.
Accounts for most of the atoms volume.
Electrons have the smallest mass
They have distinct amounts of energy ….
higher energy electrons are farther away from the nucleus
Lower energy electrons are closer to the nucleus.

4. In an atom:
the number of protons = the number of electrons.
The number of neutrons can be different.

5. Elements can be identified by the number of protons in the nucleus of its atom.
Atomic Number: the number of protons in its nucleus.
The number of protons identifies the atom.
Example: Oxygen has an atomic number of 8
Mass Number: the sum of the protons and neutrons in the nucleus of an atom.
8 O Oxygen

6. To determine the number of neutrons in an atom:
Mass Number – Atomic Number = # of Neutrons. 3 Li
Lithium
6.941
Example: Lithium has an atomic number of 3 and a mass number of which we round to 7.
Mass Number – Atomic Number = # of Neutrons
= 4 Neutrons
Therefore…. Lithium has: protons and 4 neutrons
What about electrons??????
Remember: neutral atoms (atoms with no charge) have an equal number of protons and electrons……
Therefore..... Lithium has: 3 electrons.

7. Element
Symbol
Atomic #
Atomic Mass
Protons
Neutrons
Electrons
Lithium Li 3 7 4
Phosphorous P 15 31 16
Chlorine Cl 17 35 18
Potassium K 19 39 20
Silver Ag 47
108 61
Silicon Si 14 28
Hydrogen H 1

8. Isotopes:
Atoms that have the same number of protons but different numbers of neutrons.
Example: Carbon always has 6 protons, but may have 6, 7, or 8 neutrons.
Common notations for isotopes of Carbon with 8 neutrons are C-14, Carbon- 14 or 14C

9. Bohr Model
A model used to show energy levels and where electrons may be located around the nucleus.
The energy level closest to the nucleus holds 2 electrons
The next energy level holds 8 electrons.
The third energy level can hold up to 18 electrons.
The last energy level holds electrons called valence electrons

10. To Draw a Bohr Diagram: Find your element on the periodic table.
Inside the nucleus write the number of protons and number of neutrons (determine by subtracting atomic number and atomic mass.)
Determine the number of electrons – it is the same as the atomic number.
This is how many electrons you will draw.

11. Carbon has an atomic number of 6
You will draw 6 electrons.
Remember your rules, the first shell can only have 2 electrons.
The remaining 4 electrons will go into the next energy level.
6 P
6 N

12. Valence electrons the outermost electrons from the nucleus.
The number of valence electrons give the element its chemical properties.
The greatest number of valence electrons for any atom is 8.
These electrons play a role in chemical bonding between atoms to form molecules.

13. Organizing Elements

14. Dmitri Mendeleev
a Russian scientist who discovered a set of patterns that applied to all the elements.
He noticed a pattern or properties appeared when he arranged the elements in order of increasing atomic mass.

15. The Modern Periodic Table
New elements have been added since Medeleev’s table.
Elements are arranged in order of increasing atomic number
Contains one square for each element

16. 26 Fe
Iron
55.847
Atomic Number
Symbol
Element
Atomic Mass Number

17. The Properties of an element can be predicted from its location in the periodic table.
Periods: the horizontal rows
(colored pink)
Numbered 1-7
The elements have the same # of valence shells.

18. Across the Periodic Table
Periods: Are arranged horizontally across the periodic table (rows 1-7)
These elements have the same number of valence shells.
2nd Period
6th Period

19. Groups: the vertical columns (colored blue) Also called families
Elements have similar
characteristics
Numbered 1-18
The number of valence electrons
is the same for all
elements in a
group

20. Down the Periodic Table
Family: Are arranged vertically down the periodic table (columns or group, or 1-8 A,B)
These elements have the same number electrons in the outer most shells, the valence shell.
Alkali Family:
1 e- in the valence shell
Halogen Family:
7 e- in the valence shell

21. Lewis Structures Find your element on the periodic table.
Determine the number of valence electrons.
This is how many electrons you will draw.

22. Lewis Structures Find out which group (column) your element is in.
This will tell you the number of valence electrons your element has.
You will only draw the valence electrons.

23. Groups Group 13 = 3 ve Group 14 = 4 ve Group 15 = 5 ve
(except He)
Group 1 = 1 electron
Group 2 = 2 electrons

24. C Lewis Structures Write the element symbol.
Carbon is in the 14th group, so it has 4 valence electrons.
Starting at the right, draw 4 electrons, or dots, counter-clockwise around the element symbol. C

25. C Lewis Structures Check your work.
Using your periodic table, check that Carbon is in the 14th group.
You should have 4 total electrons, or dots, drawn in for Carbon. C

26. Li
Ne Mg Cl

27. Periodic Table: Metallic arrangement
Layout of the Periodic Table: Metals vs. nonmetals
Nonmetals
Metals

28. Infamous Families of the Periodic Table
Notable families of the Periodic Table and some important members:
Alkali
Alkaline (earth)
Transition Metals
Noble Gas
Halogen
Chalcogens

29. Properties of Metals Shiny
Malleable : can be hammered or rolled into flat sheets and other shapes
Ductile: can be pulled out or drawn into a long wire.
Conductive: the ability of an object to transfer heat or electricity to another object.
Reactive: they combine or react with other elements easily.
A chemical property of metal is its reaction with water which results in corrosion.

30. Alkali metals: metals in Group 1
Hydrogen is NOT a member (it is not a metal)
React with other elements by losing one electron.
So reactive that they are never found uncombined in nature. They are only found in compounds.
Very reactive with water.
Shiny and soft so that you can cut with a knife.
Examples: sodium (Na), Lithium (Li),
Potassium (K)

31. Alkaline Earth Metals:
metals in Group 2
Fairly hard, gray-white metals
Good conductors of electricity
React by losing 2 electrons
Not as reactive as Group 1 elements
Never found uncombined in nature.
Examples: beryllium, magnesium, calcium, barium

32. Transition metals Groups 3 – 12 Most are hard and shiny
Good conductors of electricity
Less reactive then group 1 and 2
Examples: Iron, copper, nickel, gold, silver

33. Metals in Groups 13-15
Not as reactive as metals on the right side of the periodic table.
Aluminum, tin, lead

34. Lanthanides
Top row on bottom of periodic table
Soft, malleable, shiny, high conductivity
Usually mixed with other elements to form alloys: a mixture of metal with at least one other element.
Actinides:
Bottom row of bottom of
periodic table
Some are created in a lab.
Some exist in nature

35. Nonmetals: element that lacks most of the properties of a metal
Physical Properties
Poor conductors of electricity and heat
Reactive with other elements
Solid nonmetals are dull and brittle, not malleable and ductile
Have lower densities than metals
10 of the 16 are gases at room temperature
Chemical Properties
Reactive and gain or share electrons when they react with other atoms.

36. Metalloids:
elements that have characteristics of both metals and nonmetals
Properties (physical and chemical)
All are solid at room temperature
Brittle, hard and somewhat reactive
Most useful property is their varying ability to conduct electricity.
Used to make semiconductors: substances that can conduct electricity under some conditions but not under other conditions. Used to make computer chips, lasers and transistors

38. BORON FAMILY Group 13 3 valence electrons in the outer shell
Most are metals: Aluminum, Gallium, Indium Thallium
Metalloid: Boron

39. CARBON FAMILY Group 14 4 valence electrons
Atoms can gain, lose or share 4 electrons
Non-metal: Carbon (C)
Metalloids: silicon, germanium
Metals: Tin and lead

40. NITROGEN FAMILY Group 15 5 valence electrons in the outer shell
Can gain or share 3 electrons to form compounds
Non-metals: Nitrogen, phosphorous,
Metalloids: arsenic, antimony
Metals: bismuth

41. OXYGEN FAMILY Group 16 6 valence electrons in the outer shell
Can gain or share 2 electrons
Reactive
Nonmetals: Oxygen, sulfur, selenium
Metalloids: Tellurium Polonium
Metals: none

42. Halogens (salt forming)
Group 17
7 valence electrons in the outer shell
Can gain or share 1 electron
Very reactive are often bonded with elements from Group 1
Nonmetals: Flourine, chlorine, bromine, iodine
Metalloids: Astatine
Metals: none

43. Noble Gases Group 18 Exist as gases
8 valence electrons in the outer shell = Full
Helium (He) has only 2 electrons in the outer shell = Full
Not reactive with other elements
Non-metals: Helium, neon, argon, krypton, xenon, radon
No metalloids or metals