HISTORY, GROUPS, AND CHARACTERISTICS Periodic Table: HISTORY, GROUPS, AND CHARACTERISTICS

(History of) The Periodic Table Mendeleev (Russian) – 1869, was the first person to arrange elements in order by weight Made “playing cards” Arranged by mass and saw repeating patterns in properties (protons + neutrons, but he didn’t know that’s what gave them their mass), he put each of the known elements on a card with their properties, and distributed them as if they were playing cards. When put in order by mass he saw repeating patterns in their properties.

(History of) The Periodic Table Moseley (English) – 1913, discovered that each element has an atomic number (protons) Organized based on this number Improved patterns of mendeleev Periodic Law – says that when elements are arranged in order by atomic number, their physical and chemical properties show a repeating pattern → every 8 elements. Moseley (English) – 1913, discovered that each element has an atomic number (protons), by which they should be organized (this improved on the patterns seen by Mendeleev). Periodic Law – says that when elements are arranged in order by atomic number, their physical and chemical properties show a repeating pattern → every 8 elements.

So what does all this mean? Let’s look at your periodic Table

Basic Organization Groups/Families – vertical column – same # of valence electrons, which dictates their behavior (groups behave similarly) Period/Row – horizontal row – same outermost energy level, behavior changes predictably from left to right

Lets have some fun -Make a 1 by 6 chart. -Label the top row 1st period, 2nd row 2nd period and so on until the sixth row and 6th period - Put your name in one of the cells in 6th period -Put down the name of a friend in each of your class periods (other than 6th period). -a column is your school “family” or group and the row was your period. Easy right!

Check-In With your arms, show me where a Period is on the table. Again, with your arms – where is a Group?

But what can we figure out about our elements when we have a periodic table A lot actually let’s chat about it

Periodic characteristics 1. Atomic size – distance from the center of the atom (nucleus) to the outer edge of its electron cloud (measured by measuring the distance between the nuclei of two bonded atoms and dividing by two). Atomic Size protons can attract electrons and keep them close (i.e. smaller radius) Atomic Radius/ size increases as you go down

Periodic Characteristics 2. ionic size – distance from the center to the outer edge of an ion. Cation (+) → lost electrons → smaller than its atom Anion (-) → gained electrons → bigger than its atom

Check-In What will happen to Na when it makes an ion? (what will happen to its electrons?) Will Na atom or Na ion be bigger? Why? What will happen to Cl when it makes an ion? (what will happen to its electrons?) Will Cl atom or Cl ion be bigger? Why?

Let’s get this on our periodic table

Periodic Characteristics (cont.) 3. Metallic properties Luster – shiny Conductivity – able to transfer heat or electrons Malleability – can be rolled or hammered into sheets Ductility – can be drawn (pulled) into a wire (like a specific version of malleable) Explained by: cations (bonding by) floating in a sea of mobile electrons Nonmetallic properties Luster – varies Poor conductor of heat and electricity Brittle Explained by: electrons are shared tightly in bonds

Let’s get this on your periodic table!

Check-In Tell your neighbor 3 characteristic properties of metals. They tell you 3 elements they would expect to have those properties. Tell your neighbor 3 properties of non-metals. They tell you 3 elements they would expect to have those properties.

Periodic Characteristics (cont.) 4. Ionization Energy – energy needed to remove one of an atom’s electrons (1st ionization energy is required to remove the first electron, 2nd ionization energy is required to remove the second, etc.) 5. Electronegativity – the ability of an atom to attract electrons in a chemical bond (think of it as how tightly the electrons are held). Noble gases don’t have electronegativity values because they don’t participate in bonds.

Check-In What is the very most Electronegative element on the whole table? Which is the least? Between N and O, which would you expect to have a higher Ionization Energy? Between Ca and Mg, which would you expect to have a higher IE?

Groups Elements in the same group have more similarities than elements in the same period because they have the same number of valence electrons.

Check-In As I point at groups on the periodic table, say out loud how many valence electrons that group has.

Alkali Metals (Group 1) Soft, can be cut with a knife Low density and melting points React violently with water and quickly with the oxygen in the air Never found uncombined in nature (always bonded to some other element) When they bond, always give away 1 electrons (making +1 ions)

Alkaline Earth Metals (Group 2) Soft (not as soft as Alkali Metals) Higher density and melting points than Group 1 Very reactive but not as much as Group 1 Not found uncombined in nature (also always bonded to another element) When they bond, always give away 2 electrons (making +2 ions)

Transition Metals Metals with higher densities and boiling points Variable properties across the group In the d-block Very flexible with their electrons (leading to their variable properties) Still metals – tend to give away some number of electrons making (+) ions

Metalloids (say with a robot accent) Can behave more like metals or nonmetals depending on the environment they are in Touch the stairstep line on the periodic table: B, Si, Ge, As, Sb, Te

Diatomic Elements HONClBrIF (or BrINClHOF) elements – found combined with self (Br2, I2, Cl2, etc) Never appear as just one atom, if not combined with something else, they bond with another atom of the same element.

Halogens (Group 17) Form salt compounds with metals Exist as diatomic molecules Highly reactive Not free elements in nature I2 is a solid at room temperature, Br2 is a liquid, and Cl2 and F2 are gases Predictably gain one electron, making (-1) ions

Noble Gases (Group 18) Least reactive of the elements (vocab word: INERT means non-reactive) All have full valence shell (which is why they’re least reactive) All gases at room temperature