Question

In the following table, the mass number and the atomic number of certain elements are given. Element A B. C D E Mass number 1 7 14 40 40 Atomic number 1 3 7 18 20 a) How many neutrons are present in B and D? b) What would be the valency of element C
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Answer 1

Step-by-step explanation:

a. Elements D and E are isobars as they have a same mass number but a different atomic number.

b. The atomic number of element B is 3. So its electronic configuration is 2,1. Hence its valency is 1 as it has only 1 valence electron.

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Answer 2

Step-by-step explanation:

A is H atom which contains 1 proton,1 electron and 0 neutron.

B should be Lithium atom with 3 protons, 3 electrons and 4 neutrons.

C is Nitrogen atom with 7 protons , 7 electrons and 7neutrons.

D is a noble gas argon with atomic number 18 and mass number 40. D can also be a cation K+ with 18 electrons and mass number 40 40K. D can also be an anion Cl- with 18 electrons and 40Cl.

E is calcium with atomic number 20 and mass number 40

isobars differ in atomic number (or number of protons) but have the same mass number. so

isobars would be 40Ar, and 40Ca. and not isotopes. isotopes must contains same numbe rof protons but different number of neutrons.so

D will be the answer for all cation K+ , anion Cl- , noble gas argon and isobar Ar and Ca.

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