Will give brainliest! the first known telescopes, used around 1600, consisted of a lens and an eyepiece. today, telescopes are often computer controlled and consist of a complicated array of sophisticated lenses. which statement correctly describes how telescopes have changed over time? a. the telescopes of the 1600s were used until the year 2000, when a more sophisticated telescope was built. b. the telescopes of the 1600s were gradually improved upon over time, resulting in the telescopes that are available today. c. the telescopes of the 1600s were used until the year 1900, when a more sophisticated telescope was built that was used until the year 2000. d. the telescopes of the 1600s were abandoned after about 50 years, and the technology was completely replaced.

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms