1. Nonmetals Section 20.2 and 20.3

2. Nonmetals Nonmetals- gases or brittle solids at room temperature. Nonmetals- gases or brittle solids at room temperature. – not malleable or ductile. – do not conduct heat or electricity well – not shiny Nonmetals don’t conduct electricity because- electrons are strongly attracted to the nucleus Nonmetals don’t conduct electricity because- electrons are strongly attracted to the nucleus

3. Nonmetals Nonmetals- gain electrons to form anions Nonmetals- gain electrons to form anions Can form either covalent or ionic bonds Can form either covalent or ionic bonds Diatomic- molecule that consists of two atoms of the same element covalently bonded Diatomic- molecule that consists of two atoms of the same element covalently bonded –Includes H 2 Cl 2 F 2 N 2 O 2 Br 2 I 2 Hydrogen is diatomic because it is very reactive. Hydrogen is diatomic because it is very reactive. –Bonding makes it more stable

4. Nonmetals Halogens- nonmetals from group 17. Halogens- nonmetals from group 17. –very reactive. – 7 valence electrons – form reactive diatomic molecules with distinctive colors Sublimation- changing directly from a solid to a vapor Sublimation- changing directly from a solid to a vapor Noble gases- stable due to full outer energy levels. Noble gases- stable due to full outer energy levels. –don’t make compounds naturally

5. Metalloid & Allotropes Metalloid- can form ionic or covalent bonds. Metalloid- can form ionic or covalent bonds. – properties of both metals and nonmetals Allotrope- different forms of the same element Allotrope- different forms of the same element – have different molecular structures Semiconductor- element that conducts electric current under certain conditions- like Silicon Semiconductor- element that conducts electric current under certain conditions- like Silicon

6. Diamond vs. Graphite Both are made of carbon. Both are made of carbon. Diamond- clear, hard Diamond- clear, hard –each C atom bonded to four other C atoms forming a giant crystal. Graphite- black powder with hexagonal layers of C atoms. Graphite- black powder with hexagonal layers of C atoms. –Each C is bonded to 3 other C. –Layers can slide past each other, so graphite is a good lubricant.

9. Synthetic Elements Transuranium elements - elements that have an atomic number greater than 92 (uranium). Transuranium elements - elements that have an atomic number greater than 92 (uranium). –Synthetic (man made) and unstable Scientists make elements to gain an understanding of the forces holding the nucleus together Scientists make elements to gain an understanding of the forces holding the nucleus together –To develop new technologies