Question

a) Define: 1) Atomic mass number
2)Variable valency​

Answer 1

Answer:

atomic mass number...

Together, the number of protons and the number of neutrons determine an element's mass number. Since an element's isotopes have slightly different mass numbers, the atomic mass is calculated by obtaining the mean of the mass numbers for its isotopes.

variable velency...

Certain elements have more than one valency. They exhibit variable valency. For example, copper, tin, iron and mercury exhibit variable valency. Copper combines with oxygen to form cuprous oxide (Cu2O) and cupric oxide (CuO).

Answer 2

Answer:

1) Atomic mass number is the total number of protons and neutrons present ( together known as nucleons) in an atomic nucleus. The mass number is different for each different isotope of a chemical element.

2) In transition elements, an atom losses electrons from the shell next to the valence shell ( penultimate shell) . In such a situation the element exhibits more than one valency ( variable valency).

Explanation:

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