Understanding the Periodic Table: Structure, Elements, and Classification

1. The Periodic Table Chapter 17 (Section 3) and Chapter 19

2. The Periodic Table • Dmitri Mendeleev- Russian chemist who organized the elements by increasing atomic mass in the late 1800s. • Periodic- repeated in a pattern • Periodic table- the elements are arranged by increasing atomic number and by changes in physical and chemical properties. • Henry G.J. Moseley- 1913 –organized the elements according to their increasing atomic numbers.

3. Organization of the Periodic Table Period- horizontal rows • Atomic # goes up as you go from left to right Groups- -elements in the same group have similar chemical properties

4. 3 main groups: • Metals- typically hard, shiny, solid • good conductors of heat and electricity • malleable- can be rolled or hammered into thin sheets • ductile- can be drawn into wires • Nonmetals- usually a gas or a brittle solid @ room temp. • poor conductors of heat and electricity • typically not shiny • Metalloids –share some properties as metals and some properties of nonmetals

5. Metals • 1. Alakali metals- (Group 1) • H, Li, Na, K, Rb, Cs, Fr • shiny, malleable, and ductile • good conductors of heat and electricity • softer than most other metals • most reactive of all metals • not found in nature in elemental form • radioactive element- nucleus breaks down and gives off particles and energy

6. Metals • 2. Alkaline Earth Metals- (Group 2) • Be, Mg, Ca, Sr, Ba, Ra • shiny, malleable, ductile • not found in elemental form in nature • 3. Transition Elements- (Group 3-12) • often form brightly-colored compounds • Ex: Fe, Co, Ni, Cu, Ag, Au, Zn, Cd, Hg • ores- metals in the Earth’s crust that combine with other elements ex: Cu, Fe, Cr

7. Nonmetals 1. Hydrogen • 90% of atoms in the universe are H diatomic molecule- consists of 2 atoms of the same element in a covalent bond (H2) 2. Halogens (Group 17) -F, Cl, B, I, At -uses: Cl- disinfectants, I in diet- thyroid gland 3. Noble Gases (Group 18) -He, Ne, Ar, Kr, Xe, Rn -very stable- valence shell is filled uses: He- blimp, Ne and Ar- neon signs, lasers

8. Metalloids • semi-conductors- can conduct energy better than nonmetals, but not as well as metals • 1. Boron Group (Group 13) • B, Al, Ga, In, Tl • uses: B- borax for laundry, boranes used in jet fuel • Al- most abundant element in Earth’s crust • 2. Carbon Group (Group 14) • C, Si, Ge, Sn, Pb • carbon- all organic compounds have carbon • allotropes- different forms of the same element • ex: allotropes of carbon: graphite, diamond • 3. Nitrogen Group (Group 15) • N, P, As, Sb, Bi • N- 4th most abundant element in human body • uses: fertilizers • 4. Oxygen Group (Group 16) • O, S, Se, Te, Po • O2: respiration • O3: ozone- protection from the Sun’s radiation

9. Synthetic Elements (man made) • very unstable (some only exist for fractions of a second) • not typically found on Earth • smash existing elements in particle accelerator in a heavy ion accelerator