Which of the following reactions is a redox reaction? acid-base single-replacement double-replacement

What is common about these molecules? a.their atoms are held together by covalent bonds. b.they are all made up of the same two atoms. c.their atoms are held together by ionic bonds. d.they are all made up of oxygen atoms only.

Classify each statement about effective nuclear charge, zeff, as true or false.

Use examples from the article to explain one positive and one negative effect that chemistry has had on society.