The Periodic Table of the Elements

Looking for Patterns Matter is made of about 100 different elements. (118 to be exact) Some are very reactive; some are not. 1800s - scientists began to suspect elements could be organized in a useful way.

Dmitri Mendeleev (1869) – Mendeleev discovered a hidden pattern. Similar chemical & physical properties. Atomic Mass (how heavy they are) Bonding Power - # of chemical bonds an element can form (he studied reaction with oxygen)

The first periodic table Mendeleev liked to play Patience, a solitaire game. Pattern – elements arranged in order of increasing atomic mass Bonding Power – orderly pattern across rows Each column had similar properties in its own group Periodic means regular, repeating pattern.

Groups & Families An elements properties can be predicted from its location in the table. Table is arranged by 18 columns & 7 rows. Columns are called groups or families. Groups have similar characteristics. Every family member has the same number of valence electrons

Rows & Periods Each row is called a period. The number of valence electrons increase across periods. Reactivity decreases a from left to right (metals) Reactivity increases left to right (non-metals) Noble gases are stable

Metals Metals are: Great conductors - can transfer heat and electricity), shiny, Ductile – can make into wire. Malleable (easily shaped). Shiny and has high density.

Alkali metals Group 1 (Li, Na, K, Rb, Cs, Fr) VERY REACTIVE!! Only 1 valence electron They are not found in element form (usually in compound form). Soft & Shiny They tend to donate their electron

Alkaline Earth Metals Group 2: Be, Mg, Ca, Sr, Ba, Ra. Barium Esophagram Group 2: Be, Mg, Ca, Sr, Ba, Ra. Not as reactive, but good enough! Not found uncombined in nature. 2 valence electrons. Hard, gray-white, good conductor. Look! It’s Beryllium Man!!!

Transition Elements Groups 3-12. Bridge the reactive metals with less reactive elements. Fe, Cu, Ag, and Au are good examples Fairly stable!  Reacts slowly if at all. Transitions give electrons (but have different bonding rules)

Examples of Transition Metals

Lanthanides Fits into period 6. Soft, malleable, shiny, high conductivity. Used to make alloys (mixtures of metals)

Actinides Fits into Period 7 (#58-#103) Uranium and Plutonium are examples. All are radioactive! (unstable)? E.g. Americium – used in smoke detectors.

Non-metals There are 16 non-metals each located to the right of the zigzag line in the periodic table. (17 total) Very important for LIFE to exist! (CHNOPS)!

Non-metals properties Many are gases at room temperature. Some are solids. Only one is a liquid. Bad conductors, but good insulators, dull, can’t bend or shape them like metals. Big Idea!!!! – PROPERTIES OF NON-METALS ARE OPPOSITE TO THOSE THAT CHARACTERIZE THE METALS.

Non-metals – The families Boron Family Group 13 & has 3 valence electrons Carbon Family Group 14 & has 4 valence electrons Nitrogen Family Group 15 & has 5 valence electrons Oxygen Family Group 16 & has 6 valence electrons The Halogens Group 17 & has 7 valence electrons The Noble Gases Group 18 & has 8 valence electrons

What about Hydrogen???? All alone in upper left-hand corner of periodic table. Simple element. Non-metal (but has one valence electron). Every 90% of atoms in universe made of hydrogen. Combines well with oxygen (H2O) The Hindenberg – 1937 ↓

Finally, Metalloids (Also called semimetals) On the border between metals & non-metals. Shares characteristics. Most common is Silicon (Si). Varies on how it conducts electricity (depends on temperature, light, humidity, etc.) Silicone & Germanium are used to make semiconductors.

Semiconductors Under some conditions carry electricity. Used to make: Computer chips Transistor Lasers