Question

how will the tendency to gain electrons change as we go from left to right across a period Y and a Shiny brown coloured element x on heating in air becomes black in colour name the element X and the black compound formed​

Answer 1

Answer:

The tendency to gain electrons increases across a period.

X is Copper and the black compound is copper (II) oxide. (CuO).

Explanation:

As we move across the period from left to right, the tendency to gain electrons increases because the number of valance electrons, ie, the number of electrons in the outermost shell also increases. So, it is easy to gain electrons as compared to losing them.

For example, in period 3,

Elements                          |   Na   Mg   Al   Si   P   S   Cl

No. of valance electrons |    1      2      3    4    5    6    7

Now, it is difficult for Na to gain 7 more electrons to complete its octave but for Cl, it is easy as it has to gain only one electron.

Hence, the tendency to gain electrons increases across a period.

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The metal X is Copper (Cu).

And, upon reacting with oxygen, it forms black colored copper (II) oxide.

The balanced chemical reaction representing this chemical change is as below.

2Cu            +           O₂ ----------->     2CuO

(shiny brown)                                (black colored)