Answer : The chemical formula for the compound is, 
Explanation :
When the element 'M' react with the
to give
.
The balanced chemical reaction is,

In this reaction, 'M' is in mono-atomic form and
is in diatomic form.
By the stoichiometry,
2 moles 'M' react with the 1 mole of
to give 2 moles of
.
Therefore, the chemical formula of the compound is, 
Answer:
(b) fully filled valence s orbitals
Explanation:
Electron configuration of Be: 1s22s2
2s2 is fully filled
Answer:
17
Explanation:
the atomic mass is away protons + neutrons, electrons are neglatable.
Using the periodic table to choose the element that matches each description include the following below:
<h3>What is a Periodic table?</h3>
This contains elements which are arranged according to the order of their atomic number in a tabular form. There are 18 groups which are the vertical columns present while there are 8 periods which are the horizontal rows present in the periodic table.
Example of an alkali metal is potassium while the non reactive ones include argon, neon etc. Examples of halogens include chlorine, iodine etc. are the ones which have seven electrons in their outer electron shells thereby just requiring one electron to achieve to obtain a stable octet configuration.
These are therefore the elements which match the descriptions provided in this case and is the most appropriate choice.
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