An element is a pure substance Elements cannot be broken down into simpler substances chemically Atoms have no net electrical charge Hydrogen has an atomic number of 1 and a mass number of 1 Valency shell is the outermost energy level
1. The air we breath is made up of 78% a) oxygen b) carbon dioxide c) nitrogen d) hydrogen
2. The element sodium (Na) has eleven electrons what is its mass number? a) 11 b) 12 c) 20 d) 23
3. Room temperature is within which range? a) 40oF and 65o F b) 68oF and 77o F c) 78oF and 87o F d) none or these
5. The colour of chlorine (Cl2) gas a) colourless b) brown c) yellowish-green d) blue
6. Silver is written as this in the periodic table a) S b) Si c) Au d) Ag
7. A compound formed by the sharing or exchange of electrons a) ionicly bonded b) covalently bonded c) electrovalently bonded d) molecularly bonded
8. Atoms with same number of protons but different number of neutrons a) ions b) isotopes c) compounds d) metals
9. These have one, two or three electrons only in the outer shell a) liquids b) helium c) metals d) non-metals