Periodic Table of the Elements的元素周期表.ppt

* * The pnicogens possess different properties. 1. Nitrogen - A nonmetal but under standard conditions is a diatomic gas (N2) - Accepts electrons from most elements to form compounds in the –3 oxidation state - Has only positive oxidation states when combined with highly electronegative elements - Present in most biological molecules - Used agriculturally in huge amounts, as preservatives in meat products and in explosives 2. Phosphorus - A nonmetal that consists of three allotropes - Combines with active metals and hydrogen to produce compounds in which they have a –3 oxidation state - Attains oxidation states of +3 and +5 when combined with more electronegative elements - Essential for life and is used in fertilizers, toothpaste, and baking powder 3. Arsenic - A semimetal with extended three-dimensional network structures - Can combine with active metals and hydrogen to produce compounds in which they have a –3 oxidation state - Attains oxidation states of +3 and +5 when combined with more electronegative elements - Is toxic and is used in pesticides and poisons 4. Antimony - A semimetal with extended three-dimensional network structures - Unreactive metal but forms compounds with oxygen and the halogens in which the oxidation states are +3 and +5 - Used in metal alloys 5. Bismuth - A silvery metal with a pink tint, used in metal alloys - An unreactive metal but forms compounds with oxygen and the halogens in which their oxidation states are +3 and +5 * – Electronegativities of the Group-14 elements are lower than those of Groups 15–18. – All form compounds in the +4 oxidation states, so they are able to form dioxides and tetrachlorides. – Only the two metallic elements tin and lead form an extensive series of compounds in the +2 oxidation s