Group 1A(1), the alkali metals, includes lithium, sodium, and potassium. Group 7A(17) the halogens, includes chlorine, bromine, and iodine. hope this helps:)
Atoms with the same number of protons, but different numbers of neutrons are isotopes of the same element.
The number that represents the coefficient on the product side of the chemical reaction,
is 7.
<h3>Coefficients of chemical equations</h3>
In equations representing chemical reactions, the coefficient of each reactant or product of a reaction is the number that comes on the left-hand side just before the chemical formula.
The coefficient of each species in a chemical reaction is obtainable when the equation of the reaction is balanced.
For example, in the following equation: 2A + B = 3C + D
The coefficients of A, B, C, and D are 2, 1, 3, and 1 respectively.
Applying this to the product side of a chemical reaction;
It means that the coefficient of the product is 7.
More on coefficients of chemical equations can be found here: brainly.com/question/28294176
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Mass number of an element write in bottom of it!
So, there 80 would be the mass number of ₈₀Br.
Hope this helps!