Elements

1. Elements The Periodic Table: Why is it arranged this way?

2. What is an element? • Elements: Simplest form of a substance; cannot be broken down further and keep its physical and chemical properties • Atoms are the smallest particle of an element • Basic building blocks of compounds (2 or more elements combined chemically) • Make up all matter on earth • 118 elements, 92 occur naturally on Earth

3. Individual elements (“tiles”) Atomic number 79 Au chemical symbol Gold common name 196.967 Atomic mass

4. Period • Numbered rows (on left side, rows go across) • equal to the number of energy levels in an atom

5. Periods have a pattern to them: • Number of protons increases from left to right • Number of electrons increases left to right • The amount of energy needed to remove electrons increases from left to right • The size of the atom decreases as you move left to right

6. Groups (families) • Numbered columns (1 thru 18) • All elements in the group have the same number of electrons in the outer energy level • Valence electrons = outermost electrons • Elements in group react in similar ways

7. The zig-zag line: • Line in periodic table • Separates 88 elements that are metals: to left of line, nonmetals to the right

8. Metals • metals tend to lose electrons when chemically bonded with other elements • Lose electrons easily (become positive ions)

9. Properties of metals • What are some physical properties of metals? • Shiny • Ductile: can be drawn into wire • Malleable: can be flattened into sheets • Conduct heat and electricity • What are some chemical properties of metals? • Corrode : react with water (rust, tarnish,…) • React with nonmetals to form compounds

10. To the right of the line in the periodic table are nonmetals: • Nonmetals physical properties: • Dull • Brittle • Can be solids, gases, or liquids

11. Nonmetal chemical properties: • Gain electrons easily so they react with metals (Sodium reacts with chlorine: sodium chloride)

12. Metalloids • On either side of line: • Metalloids: act like both metals and nonmetals • Boron, Silicon, Arsenic

13. Specifics on Chemical Groups or Families • Group 1: Alkali Metals • Physical properties: • Soft, silver metals • Have one outer electron • Chemical Properties: • Always combine with another element, never found alone in nature • Combine especially with group 17 (VIIA) • Examples: Potassium, Sodium • Movie of potassium

14. Alkaline metals • Group 2: Alkaline Metals • Physical properties: • Good conductors, grayish white in color • Have 2 outer electrons • This makes them LESS reactive than group 1 • Chemical Properties • not as active as group 1 but still very reactive • Combine easily with Oxygen in group 16 (VIA) • Magnesium and Calcium

15. Halogens • Group 17 (VIIA): Halogens • Physical Properties • Nonmetals • Group with the only liquid nonmetal element • Chemical Properties • Very reactive: need only one electron to fill outer shell • Form salts (sodium chloride, sodium fluoride) • Fluorine, chlorine, iodine • (Some are sensitive to touch!)

16. Noble (inert) gases • Group 18 (VIIIA): Noble Gases • Physical Properties: • Gases at room temperature • Chemical Properties • Do not react easily with anything because the outer electron shell is already full! • Helium, Neon, Krypton, Radon

17. Summary • Elements: simplest form of a substance • Elements have an atomic number, atomic mass, chemical symbol • Grouped into families by how reactive the outer electron shell is • Periods are the rows across • Families share the same properties