1. Chapter 4
The Periodic Table

2. Organizing the Elements
Dmitri Mendeleev – Constructed the first Periodic Table in 1869 The elements were arranged according to their chemical properties
Vertical columns were in order of increasing atomic mass
The columns were arranged so that elements with the most similar properties were side by side

3. Mendeleev even left blank spaces for elements that he believed existed, but were not yet discovered, one example was…
Ekasilicon… now element 32 Germanium.

4. Henry Moseley – in 1913 Moseley, a British physicist determined an atomic number* for each known element and arranged the Periodic Table by order of atomic number.
This is the way the Periodic Table is arranged today.
Periodic Law: When elements are arranged in order of increasing atomic number there is a periodic repetition of Physical and Chemical properties.

5. Metals Nonmetals and Metalloids
Over 80% of the elements are Metal
Metals are...
Good Conductors of heat and electricity
Metallic luster or sheen, its ability to reflect light.
Malleable: Ability to be hammered into sheets or foil.
Ductile: Ability to be drawn into wire.
room temp (except Hg) z
Metals Nonmetals and Metalloids

6. Nonmetals are located in the upper right corner of the periodic table, to the right of the stair shaped line.
Nonmetals have a great variation in physical properties…gases, solids, one liquid Br.
Nonmetals are poor conductors, their solids are brittle.

7. Metalloids are located on the stair shaped line, outlined on our chart in green.
Metalloids have properties of both metals and non metals. In general they…
Have metallic luster
Conduct electricity, but not as well as a metal, (semiconductor)
Are brittle, they will shatter if hit with a hammer.
They are used extensively in the electronics industry for computer chips and circuits.

8. Periods – the horizontal rows of the Periodic Table.
Groups – the vertical columns of the Periodic Table.

9. Classifying the Elements
Noble gases – elements in which the outermost s and p sublevels are filled. Group 18 on the chart.
Representative elements – elements whose outermost s and p sublevels are only partially filled. Groups 1,2 and on the chart (tall)
Group 1 = alkali metals
Group 2 = alkaline earth metals
Group 17 = halogens
Group 18 = noble gases

10. cont.
3. Transition metals – elements whose outermost s sublevel and the nearby d sublevel contain electrons (Groups 3-12)
4. Inner transition metals – elements whose outermost s sublevel and nearby f sublevel contain electrons… the two rows below the table

11. 6.3 Periodic Trends
Atomic Radius: Is one half the distance between the nuclei of two atoms of the same element when the atoms are joined.
“In general, atomic size increases from top to bottom within a group and decreases from left to right across a period…”
Largest in the lower left corner.

13. cont. Ions
An Ion is an atom or group of atoms that have a positive or negative charge.
Positive and negative ions form when electrons are transferred between atoms.
Cations are positive ions… (generally metals) formed when atoms lose electrons to obtain the electron configuration of a noble gas.
Anions are negative ions… (generally nonmetals) formed when atoms gain electrons to obtain a noble gas electron configuration.

14. Ionization energy
Ionization energy – the energy required to overcome the attraction of the nuclear charge and remove an electron from a gaseous atom.
The ionization energy decreases as you move down a group of the periodic table
The ionization energy increases as you move across a period of the periodic table

16. Ionic Size
Positive ions are smaller than the atoms they are formed from
Negative ions are larger than the atoms they are formed from
Ionic size tends to increase as you move down a group in the periodic table
Ionic size tends to decrease as you move across a period in the periodic table

17. Electronegativity
Electronegativity – the tendency for the atoms of the elements to attract electrons when they are chemically combined with another element
Electronegativity tends to decrease as you move down a group in the periodic table
Electronegativity tends to increase as you move across a period in the periodic table