Why do elements in the same group/family have similar properties?

1. Why do elements in the same group/family have similar properties?

2. Valence Electrons • Elements in a group have similar properties • they have the same number of valence e-

3. Representative Elements • Elements in groups 1A through 8A

4. Hydrogen • 1 valence e- • Lavoisier: • Named b/c it forms water • Hydro (water) genes (to form) • Cavendish • Flammable air • Easily reacts with air

5. Alkali Metals • Group 1A • Most reactive metals • Reactivity increases from the top to the bottom. • Many are kept under oil to prevent reacting with water or oxygen.

6. Alkali Metals • One Valence e- • Forms atoms with +1 charge • Soft • Found in nature only in a compound • NaCl (Table salt) • Form bases

7. Alkaline Earth Metals • Group 2A • 2 Valence Electrons (form 2+ ion) • Reactivity shown by reactivity with water • Harder: not as reactive as 1A • Hard water • Form bases

8. Boron Family • Group 3A • 3 Valence electrons • 1 metalloid (Boron) • Five metals • Aluminum is the most abundant metal in the Earth’s crust. • Usually combined with oxygen

9. Carbon Family • Group 4A • 4 Valence Electrons • Wide range of properties • 1 Nonmetal • 2 Metalloids • 3 Metals • Most of the compounds in your body contain carbon.

10. Carbon cont • Forms allotropes • Forms of an element with different structures and properties • Silicon: 2nd most abundant element in the earth’s crust after oxygen • (glass, sand, quartz)

11. Nitrogen Family • Group 5A • 5 Valence Electrons • Very different properties • Nitrogen: • 78% of atmosphere • Forms explosive compounds • Fertilizer

12. Nitrogen Continued • Phosphorus • 2 allotropes

13. Oxygen Family • Group 6A • 6 valence e- • Oxygen has 2 allotropes • Sulfur has 10 allotropes

14. Halogens • Group 7A • 7 Valence electrons • Forms ions with -1 charge • Known as “Salt Formers” • Forms compounds with almost all metals • 5 nonmetals • 1 Unknown: (Astatine: radioactive no known uses)

15. Noble Gases • Group 8A • 8 Valence Electrons • Un-reactive • Odorless and colorless • Used in light bulbs

16. Properties of Metal, Nonmetals,and Metalloids

17. Metals versus Nonmetals • Metals tend to form cations. • Nonmetals tend to form anions.

18. Metals Tend to be lustrous, malleable, ductile, and good conductors of heat and electricity.

19. Nonmetals • Dull, brittle substances that are poor conductors of heat and electricity. • Tend to gain electrons in reactions with metals to acquire noble gas configuration.

20. Metalloids • Have some characteristics of metals, some of nonmetals. • For instance, silicon looks shiny, but is brittle and fairly poor conductor.

21. Ionization: holding on to e- • Electronegitivity: how much I want another e-

22. Answer: • Because each group/ family has the same amount of valence electrons • it’s useful in predicting atomic structure and, therefore, chemical properties.