The half-life of a specific element was calculated to be 5,200 years. what percentage of a sample of the pure element will remain after two half-lives?

25% will be remaining.

Explanation: Half live is the time in which the a radioactive substance remains half of its initial amount.

Given half life is 5200 years. let's say we have 100 grams(assume any amount of the element). In one half life(5200 years), half of it's initial amount that is 50 grams will be remaining. Now, in second half life, 25 grams of the element will be remaining.

Percentage of the remaining element =

percentage of the remaining element =  = 25%

So, 25% of the element will be remaining in two half lives.

answer: option (b) is the correct answer.

explanation:

a covalent bond is formed by sharing of electrons. whereas polarity arises due to difference in electronegativity of two atoms.

therefore, more is the electronegativity of an atom which combines with the titanium, more readily it will induce a partial positive and negative charge.

thus, out of the given options fluorine is most electronegative and has an incomplete octet. therefore, it will readily combine with titanium to share the electrons and complete its octet.