Periodicty——Trends of chemical properties元素周期性—化学性质的趋势.pptx

;Contents;; ; 1、Position in Group 18: He, Ne, Ar, Kr … 2、They have complete valence energy levels with 8 electrons, achieving octet stable structure. 3、Properties: ? They are colourless gases. ? They are monatomic: they exist as single atoms. ? They are very unreactive. ;?;; 1、Group 1, 2, 13: No. of VEs is 4. Properties: ? They are readily to lose electrons. ? They are metals generally. 2、Group 15, 16, 17: : No. of VEs is 4. ? They are readily to gain electrons ? They are nonmetals generally ; 3、Group 14: No. of VEs is = 4. Properties: ? They are metalloids ? They usually for covalent bonds (share electrons) with other atoms ;; 1、Position: Group 1 →→ Li, Na, K, Rb, Cs, Fr ; 1、Position: Group 1 →→ Li, Na, K, Rb, Cs, Fr Properties: (1) They are readily to lose e- as the No. of VEs is = 1. (2) No. of energy levels increases down the group. (3) Atomic radii increase. (4) Electronegativity decreases (5) Reactivity increases down the group. ;?;?; (2) Li reacts with water. ; (3) K reacts with water. ; (4) General equation for alkali metals reacting with water. ; (5) Reactivity of alkali metals increases down the group. Observation: The reaction with water is more and more vigorous down the group Reason: Introduced above ;?;; 1、Position: Group 17 → F2, Cl2, Br2, I2 Characters: (1) easy to gain one e- as the No. of VEs is = 7. (2) They are non-metals, existing as diatomic molecules. (3) No. of energy levels increases down the group. (4) Atomic radii incre