1. Chapter 6 The Periodic Table & Periodic Law
Mr. Stripling
Pre-AP Chemistry
Room 402

2. Development of the Periodic Table
Early model by Antoine Lavoisier

3. John Newlands
Proposed an organizational scheme for elements
When elements are arranged by atomic mass, properties repeated every eighth element
Repeating pattern = PERIODIC

4. Problems with the law of octaves:
But… Newlands called it the law of octaves (after the musical octave where notes repeat every eighth tone)
Problems with the law of octaves:
Did not work with all known elements
Fellow scientists hated octave (too unscientific for them)
Over the years Newlands was found to be basically correct.
There WAS a repeating (PERIODIC) pattern for the properties of elements

5. Dmitri Mendeleev, 1869
Demonstrated connection between atomic mass and elemental properties
Organized elements by increasing atomic mass into columns with similar properties
Predicted properties of undiscovered elements that have since been found

6. Mendeleev’s version was not 100% correct
The arrangement of elements by mass resulted in elements of different properties being placed together
Mosely, 1913
Discovered elements contain a unique number of protons
Mosely arranged elements by increasing atomic number
Resulted in a clear periodic pattern of properties
Came to be known as periodic law

7. The Modern Periodic Table
Consists of boxes containing the element name, symbol, atomic number, and atomic mass
These boxes are arranged in order of increasing atomic number into a series of columns called groups/families and rows called periods

8. Total number of periods = 7
Total number of groups/families = 18
Elements in groups 1, 2, and are referred to as representative elements due to possessing a wide range of chemical and physical properties
Elements in groups 3-12 are classified as transition elements

9. Metals are element that are generally shiny when smooth and clean, solid at room temperature, and good conductors of heat and electricity
Most metals are malleable and ductile

10. Group 1 elements (EXCEPT HYDROGEN) are known as the alkali metals
Due to having a high reactivity, alkali metals typically are found as compounds (chemical combination of two or more elements)

11. Group 2 is made of the alkaline earth metals which also possess a level of high reactivity

12. The transition elements are divided into transition metals and inner transition metals
The two sets of inner transition metals are known as the lanthanide and actinide series are located at the bottom of the periodic table
The rest of the elements in groups 3-12 make up the transition metals

13. Nonmetals are elements that are usually gases or brittle, dull-looking solids
Nonmetals are poor conductors of heat and electricity

14. Halogens comprise group 17 of the periodic table
Halogens are highly reactive and are also often found as parts of compounds

15. Noble gases comprise group 18
Noble gases are extremely unreactive
Used in lasers, light bulbs, and neon signs

16. Metalloids have physical and chemical properties of both metals and nonmetals

17. Classwork
Problems 4, 5, and 7 on page 181
Due tomorrow

18. Classification of the Elements
Valence electrons are the electrons in the highest principal energy level of an atom
Group 1 elements have similar chemical properties because they have the same number of valence electrons

19. The s-, p-, d-, and f-Block Elements
Because there are four different energy sublevels (s, p, d, and f) the periodic table is divided into four blocks, giving the table it’s odd shape

20. The s-block is made of groups 1 and 2, plus helium
Group 1 elements have partially filled s orbitals containing one valence electron and an electron configuration ending in s1
Group 2 elements have completely filled s orbitals containing two valence electrons and an electron configuration ending in s2

21. After the s sublevel is filled the valence electrons next fill the p sublevel
The p-block is comprised of groups 13-18
The three p orbitals can hold a maximum of six electrons

22. The d-block contains the transition metals
The aufbau principle states that the 4s orbital has a lower energy level than the 3d orbitals and is therefore filled first
The five d orbitals can hold ten electrons
That is why the d-block spans ten groups on the periodic table

23. The f-block contains the inner transition metals
Characterized by a filled or partially filled s orbitals and filled or partially filled 4f and 5f orbitals
The electrons of the f sublevel are not always predictable
Has seven orbitals and spans 14 columns on the periodic table

24. Classwork
Do problems 8, 9, 10, and 12 on page 186
Due Monday

25. Periodic Trends – Atomic Radius
Atom size is dependent on electron configuration
Atom size is defined by how close an atom is to another atom
Atomic Radius – half the distance between adjacent nuclei in a crystal of an element
Elements that occur as molecules, atomic radius is defined as half the distance between nuclei of identical atoms that are chemically bonded together

26. There is a decrease in atomic radii going from left to right across a period
Decreasing atomic radii is caused by increasing positive charge

27. Atomic radii increases as you move down a group
The increased number of orbitals means that electrons are further from the nucleus, increasing the atomic radius

28. Ionic Radius Ions are formed by atoms gaining or losing electrons
Ion – an atom or a bonded group of atoms that has a positive or negative charge
Atoms that lose electrons and form positively charged ions become smaller
The electron lost will be a valence electron, resulting in a smaller radius

29. Atoms that gain electrons gain a negative charge and become larger

30. In general, moving left to right across a period, the size of positive ions decrease
In groups 15 and 16, the size of the negative ions also begin to decrease
Moving down groups, the size of the ionic radii tend to increase

31. Ionization Energy
The energy required to remove an electron from a gaseous atom
How strongly an atom’s nucleus holds onto its valence electrons
High ionization energies indicate atoms are less likely to lose electrons

32. When a sodium atom loses its single valence electron to form a 1+ sodium ion, its electron configuration changes
The new configuration matches neon, demonstrating the octet rule
Octet rule – atoms tend to gain, lose, or share electrons in order to acquire a full set of 8 valence electrons

33. Electronegativity
Indicates the relative ability of an element’s atoms to attract electrons in a chemical bond
Tends to decrease while moving down groups
Tends to increase moving left to right across a period

36. Classwork – Section 6.3 #16 & 19 on page 189 #21 on page 194
Due tomorrow