Chem 107 Test 1 Pnge 3 14. Idenaify the following as lemets or comp a)oxygen d) salt of r 15. Are elements and compounds subdivisions 11 substances mixtures 16 Identify the following as chemical symbols or a) co b) Co c) Cs d) cs 17. What group of elements are good heat and electric conductors? 18. What group of elements are often brittle solids or gaseous? 19. What group of elements were once considered inert? Solution 14. Oxygen and iron are elements while water and salt are compounds. A compound contains atoms of different elements chemically combined together in a fixed ratio. An element is a pure chemical substance made of same type of atom. Water is composed of hydrogen and oxygen (H 2 O) and salt is composed of sodium and chlorine (NaCl) 15. Elements and compounds are subdivisions of substances (pure substances) and not mixtures. Mixtures are made up of elements or compounds or both in any ratio. 16. a) Formula of carbon monoxide b) Symbol of Cobalt c) Symbol of cesium d) Formula of carbon monosulfide How to tell the difference is that in an element only the first letter is written in capitals. If both letters are in capitals then, it represents a compound. 17. Metals are good heat and electrical conductors. (example Group 1) 18. Non-metals are brittle solids or gases. (example Group 7) 19. Noble gases were once considered inert (Group18 or 8A) as they had completed octets, it was thought that they couldn’t form compounds. .

1. Chem 107 Test 1 Pnge 3 14. Idenaify the following as lemets or comp a)oxygen d) salt of r 15.
Are elements and compounds subdivisions 11 substances mixtures 16 Identify the following as
chemical symbols or a) co b) Co c) Cs d) cs 17. What group of elements are good heat and
electric conductors? 18. What group of elements are often brittle solids or gaseous? 19. What
group of elements were once considered inert?
Solution
14. Oxygen and iron are elements while water and salt are compounds. A compound contains
atoms of different elements chemically combined together in a fixed ratio. An element is a pure
chemical substance made of same type of atom.
Water is composed of hydrogen and oxygen (H 2 O) and salt is composed of sodium and chlorine
(NaCl)
15. Elements and compounds are subdivisions of substances (pure substances) and not mixtures.
Mixtures are made up of elements or compounds or both in any ratio.
16. a) Formula of carbon monoxide
b) Symbol of Cobalt
c) Symbol of cesium
d) Formula of carbon monosulfide
How to tell the difference is that in an element only the first letter is written in capitals. If both
letters are in capitals then, it represents a compound.
17. Metals are good heat and electrical conductors. (example Group 1)
18. Non-metals are brittle solids or gases. (example Group 7)

2. 19. Noble gases were once considered inert (Group18 or 8A) as they had completed octets, it
was thought that they couldn’t form compounds.