Which of the following pairs is incorrect? The correct name for Ca^2+ is A line

Question

Which of the following pairs is incorrect? The correct name for Ca^2+ is A line in the spectrum of atomic mercury has a wavelength of 25-4 nm. When mercury emits a photon of light at this wavelength, the frequency of this light is Which of the following frequencies corresponds to light with the longest wavelength? You are given a compound with the formula MCI_2:in which M is a metal. You are told that the metal ion has 26 electrons. What is the identity of the metal? How many oxygen atoms are there in one formula unit of Ca_3(PO_4)_2?

Explanation / Answer

1. E) all of the above pair are correct.

2. C) calcium (II) ion

3. A) 1.18 X 1015 s-1

calculation:

relation of wavelenth and fequency: n = c (velocity of light) / wavelength

c = 3 x 108 m/s, wavelength = 254 nm = 2.54 X 10-9 meter

now, frequency n = 3 X108 / 2.54 X 10-9

n = 1.18 X1015 s-1

4. A) 4.12 X105

from above equation: wavelength = c / frequency (n)

Hence, lower the value of frequency (n) larger the value of wavelength.

5. C) Ni

MCl2 is indicatting the +2 oxidation state of metal and given that metal ion M+2 has 26 electrons

So total number of electrons in neutral atom M = 26 + 2 = 28

number of electron = atomic number = 28 belongs to Ni

6. B) 8

Ca3(PO4)2 can be written as: Ca3P2O8 so number of oxygen atom = 8

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