1. Chapter 11: Atoms, Elements, Compounds, and Mixtures Table of Contents Section 3: Compounds and Mixtures Section 1: Models of the Atom Section 2: The Simplest Matter

5. The Periodic Table The Simplest Matter 2

17. 2 Section Check Question 1 An element is matter made of only _______ kind of atom. A. one B. two C. three D. four NC: 4.03

18. 2 Section Check Answer The answer is A. Aluminum is an example of an element. NC: 4.03

19. 2 Section Check Question 2 Chemists organize all the known elements on a particular chart known as the _______. It is called the periodic table of the elements. Not only does the periodic table organize the known elements, it helps predict properties of those that have yet to be discovered. Answer NC: 4.03

20. 2 Section Check Question 3 Chlorine-35 has 18 neutrons in its nucleus, while chlorine-37 has 20. How can these both be chlorine atoms? NC: 4.03

21. 2 Section Check Answer Chlorine-35 and chlorine-37 are isotopes. Atoms of the same element can have different numbers of neutrons, as long as they have the same number of protons. NC: 4.03

32. Section Check 3 Question 1 A substance whose smallest unit is made up of atoms of more than one element bonded together is a _______. A. compound B. element C. isotope D. mixture NC: 4.02

33. Section Check 3 Answer The correct answer is A. An everyday example of a compound Is H 2 O – water. NC: 4.02

34. Section Check 3 Question 2 H 2 0 2 is the _______for hydrogen peroxide. It is the chemical formula. Even a small difference in chemical formulas can result in very different substances. Answer NC: 4.02

35. Section Check 3 Question 3 Two or more substances that come together without making a new substance form _______. A. allotrope B. element C. mixture D. solution NC: 4.02

36. Section Check 3 Answer The answer is C. You can change the proportions of the substances in a mixture without changing the identity of the mixture itself. NC: 4.02