c. Fe c. Cu B. Choose the correct option. 1. Which out of the following cannot be broken down into simpler substances by chemical means? a. Element b. Compound c. Mixture d. Molecule 2. What is the chemical symbol of iron? a. Ir b. 1 d. F 3. Which of the following represents the chemical formula of a compound? а. С C b. Ca d. CO2 4. What are the new substances (elements/compounds) formed in a chemical reaction called? a. Rust b. Products C. Mixtures d. Reactants 5. What is the substance responsible for the browning of cut surfaces of vegetables and fruits called? b. Melanin C. Rust d. Copper 6. Which of the following elements exist as tetratomic molecules? a. Hydrogen b. Nitrogen C. Potassium d. Phosphorous 7. What is the chemical formula for sodium oxide? a. Nao C. NaO, 8. Which gas is released in reaction of vinegar with baking soda? a. Oxygen b. Nitrogen C. Carbon dioxide d. Carbon monoxide 9. Which of the following elements exhibits valency 2? a. Oxygen b. Sodium C. Aluminium d. Nitrogen 10. Which of the following represents an element? a. NaCl b. C12 d. KCI a. Zinc b. Na d. Na,O2 C. HCI
Answers
compound ions present name
NaCl Na+, Cl− sodium chloride
KI K+, I− potassium iodide
CaS Ca2+, S2− calcium sulfide
CsBr Cs+, Br− cesium bromide
MgO Mg2−, O2− magnesium oxide
In the formulas of ionic compounds, simple ions are represented by the chemical symbol for the element: Cl means Cl−, Na means Na+, and so on. When individual ions are shown, however, the charge is always included. Thus, the formula of potassium bromide is given as KBr, but, when the potassium and bromide ions are shown individually, they are written K+ and Br−
Common simple cations and anions
cation name anion name
H+ hydrogen H− hydride
Li+ lithium F− fluoride
Na+ sodium Cl− chloride
K+ potassium Br− bromide
Cs+ cesium I− iodide
Be2+ beryllium O2− oxide
Mg2+ magnesium S2− sulfide
Ca2+ calcium
Ba2+ barium
Al3+ aluminum
Ag+ silver
Common ions that form multiple cations
*Mercury(I) ions always occur bound together to form Hg22+.
ion systematic name alternate name
Fe3+ iron(III) ferric
Fe2+ iron(II) ferrous
Cu2+ copper(II) cupric
Cu+ copper(I) cuprous
Co3+ cobalt(III) cobaltic
Co2+ cobalt(II) cobaltous
Sn4+ tin(IV) stannic
Sn2+ tin(II) stannous
Pb4+ lead(IV) plumbic
Pb2+ lead(II) plumbous
Hg2+ mercury(II) mercuric
Hg22+(*) mercury(I) mercurous