2.)The star nearest to Earth is Proxima Centauri, located at a distance of about

Question

2.)The star nearest to Earth is Proxima Centauri, located at a distance of about 4.2 light years. (a) If one could travel there at 99% of the speed of light (0.99c), what would be the apparent distance to the star? (b) If you traveled to Proxmia Centauri at this high velocity, stayed there for 2 years, and then returned (also at 0.99c), how much time would have passed on Earth?

4.) How many electron states are there in the following shells: (a) n = 4, (b) n = 1, (c) n = 3, (d) n = 2?

5.) A sample of a certain metal has a volume of 4.0E-3 m3. The metal has a density of 9.0 g/cm3 and a molar mass of 60 g/mol. The atoms are bivalent. How many conduction electrons (or valance electrons) are in the sample?

Explanation / Answer

4 .

number of electrons =2n2

a) number of electron=2*16=32

b) number of electrons =2*1=2

c) number of electrons =2*9=18

d) number of electrons= 2*4 =8

5. mass = density *volume =9*103*4*10-3 =36 kg

mole = mass / molar mass =36/60*10-3 =6*102

number of electron = mole *NA =6*102 *6.022*1023 =36.132*1025

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