form4 chem homework

2009-09-26 6:46 pm

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1. explain why neon gas is monoatomic

2. which element in the 2nd period would have the highest melting point? explain

3.across a period, the elements domestrate a gradual change in some of their physicalproperties. state one.

4. Xenon(Xe) is a group 0 element, explain what will happen is a ballon filled with xe is released from the top of a tower.
( relative atomic mass N=14.0 O=16.0 Xe=131.3

5.10BCl3 and 11BCl3 are compound formed respectively from two isotopes of boron-10 and boron-11 with Cl. 10BCl3reacted with water to give white fumes. explain the expected observation when 11BCl3 is added to water.

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回答 (1)

micatkie

2009-09-26 7:15 pm

✔ 最佳答案

1.
The electronic arrangement of neon is 2, 8. Neon atom is stable because the outermost shell is completely filled.

2.
carbon (diamond)
This is because carbon atoms (in diamond) are held together by a network a strong covalent bonds, and it is necessary to break almost all covalent bonds on melting.

3.
melting point

4.
The balloon falls down.
Air contains about 80% of N2 and 20% of O2. Since the molar mass of Xe is much higher than that of N2 and that of O2, the density of Xe is thus much higher than that of air.

5.
White fumes are observed.
10B and 11B are isotopes. They are the same element, and thus they have the same chemical properties. Therefore, 10BCl3 and 11BCl3 also have the same chemical properties.

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