Element a has a half-life of 10 days. a scientist measures out 200 g of this substance. after 30 days pass, the scientist reexamines the sample. how much element a will remain in the sample?

Amount of element A remaining is 25g

Explanation:

Half-life of an element is the time require for it to reduce to half of its original size.

Given that the half-life of Element A is 10days.

For a 200g ,at the end of first 10days ,it would have reduced to 100g( its half)

At the end of another 10days ,100g would have reduced to 50g(its half)

At the end of another 10days,50g would have reduced to 25g(its half)

Therefore at the end of 30days(10+10+10) the amount of Element A remaining is 25g.

b. atoms in metallic solids are not arranged in a regular pattern

explanation:

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).