The Periodic Table

Organizing the Elements OBJECTIVES: Identify three broad classes of elements.

Organizing the Elements OBJECTIVES: Explain how elements are organized in a periodic table.

What is an Element? Before we begin let us first talk about what an element is… An element is a material which cannot be broken down or changed into another substance using chemical means they are made of atoms They are floating all around us all the time They are what makes life function Without elements you would not exist

Remember the Atom Atom- The basic unit of matter made up of three subatomic particles Protons- positively charged Located in the nucleus Neutrons- no charge Electrons- negatively charge Encircling the nucleus

The Atom Now the protons and neutrons stay in the nucleus and most often do not undergo reactions When the nucleus is disrupted the results are severe… i.e. Star Formation Nuclear explsion

The Atom That leaves us with the electron… Electrons float around the nucleus They reside in levels and the outermost level is the valance level/shell This is where the valance electrons reside These are the electrons in the outermost shell and these are the electrons that undergo chemical reactions Now remember these electrons can be lost or gained resulting in a change in charge of the atom (more on this later)

Elements So back to the elements for a moment Elements are represented by symbols The elemental symbols are either a single letter or a series of letters (2 or 3) A capital letter always represents a new element If an element has another letter the second/third letters are always lower case i.e. C represents Carbon Co represents Cobalt CO represents Carbon and Oxygen (Carbon Monoxide)

Atomic Number? So what is the Atomic Number? The atomic number is the atom’s number It is the number of protons in a given element Therefore the number of protons always defines the element For neutral atoms the atomic number is also the number of neutrons and electrons Because neutral atoms will have the same number of electrons and protons And unless the atom is an isotope the number of protons and neutrons are always the same

Useful Definitions Isotope- an atom with a different number of neutrons than protons Neutrons have been lost or gained Mass Number- the mass of an atom made up of the neutrons and protons The Periodic Table of Elements actually use the average mass of all the isotopes of the element

Back to the Periodic Table The elements are all arranged for us on the Periodic Table of Elements

Why is the Periodic Table important to me? The periodic table is the most useful tool to a chemist. You get to use it on every test. It organizes lots of information about all the known elements.

Pre-Periodic Table Chemistry … …was a mess!!! No organization of elements. Imagine going to a grocery store with no organization!! Difficult to find information. Chemistry didn’t make sense.

Dmitri Mendeleev: Father of the Table HOW HIS WORKED… Put elements in rows by increasing atomic weight. Put elements in columns by the way they reacted. SOME PROBLEMS… He left blank spaces for what he said were undiscovered elements. (Turned out he was right!) He broke the pattern of increasing atomic weight to keep similar reacting elements together.

The Current Periodic Table Mendeleev wasn’t too far off. Now the elements are put in rows by increasing ATOMIC NUMBER!! The horizontal rows are called periods and are labeled from 1 to 7. The vertical columns are called groups are labeled from 1 to 18.

Organizing the Elements A few elements, such as gold and copper, have been known for thousands of years - since ancient times Yet, only about 13 had been identified by the year 1700. As more were discovered, chemists realized they needed a way to organize the elements.

The Periodic Law says: When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties. Horizontal rows = periods There are 7 periods Vertical column = group (or family) Similar physical & chemical prop. Identified by number & letter (IA, IIA)

Areas of the periodic table Three classes of elements are: 1) metals, 2) nonmetals, and 3) metalloids Metals: electrical conductors, have luster (shine), ductile, malleable Nonmetals: generally brittle and non-lustrous, poor conductors of heat and electricity

Areas of the periodic table Properties of non-metals Some nonmetals are gases (O, N, Cl) some are brittle solids (S) one is a fuming dark red liquid (Br) Notice the heavy, stair-step line? Metalloids/Semimetals: border the line-2 sides Properties are intermediate between metals and nonmetals

Classifying the Elements OBJECTIVES: Describe the information in a periodic table.

Squares in the Periodic Table The periodic table displays the symbols and names of the elements, along with information about the structure of their atoms: Atomic number and atomic mass

What does the information in the box tell me? 1 H Hydrogen 1.008 Atomic Number = # of protons Elemental Symbol Atomic Mass = # of protons plus neutrons Element Name

Element Square

Groups of elements - family names Group IA – alkali metals Forms a “base” (or alkali) when reacting with water (not just dissolved!) Group 2A – alkaline earth metals Also form bases with water; do not dissolve well, hence “earth metals” Group 7A – halogens Means “salt-forming”

The Groups of the Periodic Table Group 1: The Alkali Metals Most reactive metals on the PT Rarely found free in nature Charge of 1—1 valence electron Group 2: The Alkaline Earth Metals Still quite reactive Charge of 2—2 valence electrons

T he Groups of the Periodic Table Groups 3-12: Transition Metals Found freely and in compounds in nature Charge is usually 2 but can vary—usually 2 valence electrons Group 13: Boron Family Charge is 3—3 valence electrons

The Groups of the Periodic Table Group 14: The Carbon Family Contains elements that can form unusual bonds (carbon and silicon) Charge is +4 or -4—contains 4 valence electrons Group 15: The Nitrogen Family Charge is -3—contains 5 valence electrons

The Groups of the Periodic Table Group 16: The Oxygen Family Also known as the chalcogens Charge is -2—6 valence electrons Group 17: The Halogens Most reactive nonmetals charge is -1—7 valence electrons Group 18: The Noble Gases (The Inert Gases) Nonreactive Charge is 0—2 or 8 valence electrons

The Periodic Table Column = Group or Family 18 columns on the Periodic Table Row = Period 7 rows on the Periodic Table

Metals, Nonmetals, and Semi-metals Only nonmetal on the metal side Nonmetals are on the right of the stair-step Metals are to the left of the stair- step Semi-metals, “metalloids,” touch the stair-step

Special Rows on the PT Lanthanides Actinides

Classifying the Elements OBJECTIVES: Distinguish representative elements and transition metals.

Groups…Here’s Where the Periodic Table Gets Useful!! Elements in the same group have similar chemical and physical properties!! (Mendeleev did that on purpose.) Why?? They have the same number of valence electrons. They will form the same kinds of ions.

Families on the Periodic Table Columns are also grouped into families. Families may be one column, or several columns put together. Families have names rather than numbers. (Just like your family has a common last name.)

Elements in the 1A-7A groups are called the representative elements outer s or p filling 1A 8A 2A 3A 4A 5A 6A 7A

The group B are called the transition elements These are called the inner transition elements, and they belong here

Hydrogen Hydrogen belongs to a family of its own. Hydrogen is a diatomic, reactive gas. Hydrogen was involved in the explosion of the Hindenberg. Hydrogen is promising as an alternative fuel source for automobiles

Alkali Metals 1st column on the periodic table (Group 1) not including hydrogen. Very reactive metals, always combined with something else in nature (like in salt). Soft enough to cut with a butter knife

Group 1A are the alkali metals (but NOT H) Group 2A are the alkaline earth metals H

Alkaline Earth Metals Second column on the periodic table. (Group 2) Reactive metals that are always combined with nonmetals in nature. Several of these elements are important mineral nutrients (such as Mg and Ca

Transition Metals Elements in groups 3-12 Less reactive harder metals Includes metals used in jewelry and construction. Metals used “as metal.”

Boron Family Elements in group 13 Aluminum metal was once rare and expensive, not a “disposable metal.”

Carbon Family Elements in group 14 Contains elements important to life and computers. Carbon is the basis for an entire branch of chemistry. Silicon and Germanium are important semiconductors.

Nitrogen Family Elements in group 15 Nitrogen makes up over ¾ of the atmosphere. Nitrogen and phosphorus are both important in living things. Most of the world’s nitrogen is not available to living things. The red stuff on the tip of matches is phosphorus.

Oxygen Family or Chalcogens Elements in group 16 Oxygen is necessary for respiration. Many things that stink, contain sulfur (rotten eggs, garlic, skunks,etc.)

Halogens Elements in group 17 Very reactive, volatile, diatomic, nonmetals Always found combined with other element in nature . Used as disinfectants and to strengthen teeth.

Group 8A are the noble gases Group 7A is called the halogens

The Noble Gases

The Noble Gases Elements in group 18 VERY unreactive, monatomic gases Used in lighted “neon” signs Used in blimps to fix the Hindenberg problem. Have a full valence shell.

Electron Configurations in Groups Elements can be sorted into 4 different groupings based on their electron configurations: Noble gases Representative elements Transition metals Inner transition metals Let’s now take a closer look at these.

Electron Configurations in Groups 1) Noble gases are the elements in Group 8A (also called Group18 or 0) Previously called “inert gases” because they rarely take part in a reaction; very stable = don’t react Noble gases have an electron configuration that has the outer s and p sublevels completely full

Electron Configurations in Groups Representative Elements are in Groups 1A through 7A Display wide range of properties, thus a good “representative” Some are metals, or nonmetals, or metalloids; some are solid, others are gases or liquids Their outer s and p electron configurations are NOT filled

Electron Configurations in Groups Transition metals are in the “B” columns of the periodic table Electron configuration has the outer s sublevel full, and is now filling the “d” sublevel A “transition” between the metal area and the nonmetal area Examples are gold, copper, silver

Electron Configurations in Groups Inner Transition Metals are located below the main body of the table, in two horizontal rows Electron configuration has the outer s sublevel full, and is now filling the “f” sublevel Formerly called “rare-earth” elements, but this is not true because some are very abundant

Elements in the 1A-7A groups are called the representative elements outer s or p filling 1A 8A 2A 3A 4A 5A 6A 7A

The group B are called the transition elements These are called the inner transition elements, and they belong here

Group 1A are the alkali metals (but NOT H) Group 2A are the alkaline earth metals H

Group 8A are the noble gases Group 7A is called the halogens

1s1 1s22s1 1s22s22p63s1 1s22s22p63s23p64s1 1s22s22p63s23p64s23d104p65s1 1s22s22p63s23p64s23d104p65s24d10 5p66s1 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s1 H 1 Li 3 Na 11 K 19 Rb 37 Cs 55 Fr 87 Do you notice any similarity in these configurations of the alkali metals?

1s2 1s22s22p6 1s22s22p63s23p6 1s22s22p63s23p64s23d104p6 1s22s22p63s23p64s23d104p65s24d105p6 1s22s22p63s23p64s23d104p65s24d10 5p66s24f145d106p6 He Do you notice any similarity in the configurations of the noble gases? 2 Ne 10 Ar 18 Kr 36 Xe 54 Rn 86

Elements in the s - blocks Alkali metals all end in s1 Alkaline earth metals all end in s2 really should include He, but it fits better in a different spot, since He has the properties of the noble gases, and has a full outer level of electrons.

The P-block p1 p2 p3 p4 p6 p5

Each row (or period) is the energy level for s and p orbitals. 1 2 3 4 5 6 7 Period Number Each row (or period) is the energy level for s and p orbitals.

The “d” orbitals fill up in levels 1 less than the period number, so the first d is 3d even though it’s in row 4. 1 2 3 4 5 6 7 3d 4d 5d

f orbitals start filling at 4f, and are 2 less than the period number 1 2 3 4 5 6 7 4f 5f f orbitals start filling at 4f, and are 2 less than the period number