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MODULE 1 WORKSHEET 9 IONIC AND COVALENT BONDING Syllabus reference 8.2.3 1 Complete the following to check your understanding. a element Every pure substance is either an _______________ or a compound. A compound is either ionic molecular or _______________ in nature. b ions Ionic compounds are composed of oppositely charged _______________. Although ionic compounds are made up of charged particles, the overall compound is electrically neutral negative _______________. This means that the total number of positive and _______________ charges equal are _______________. c cations loses The positively charged ions, called _______________, are formed when an atom _______________ negative electrons. These positive ions are attracted to the _______________ ions, called anions, which are gains formed when an atom _______________ electrons. The result of this attraction is the formation ionic attractive of an _______________ compound held together by _______________ forces. The charges on the Periodic monatomic ions can be determined by the position of the element in the _______________ Table. d ratio The formula of an ionic compound is actually the _______________ in which the ions are present. This can be easily determined because the overall charge on an ionic compound must neutral be _______________. As this formula gives a ratio rather than actual numbers of ions, it is empirical called an _______________ formula. e atoms Molecules are composed of two or more _______________. These atoms, are held together sharing covalent by _______________ electrons between pairs of atoms. This sharing is called _______________ bonding. Covalent molecular substances may be elements, when the atoms are the same compounds _______________ or _______________ when the atoms are different. Copyright © 2008 McGraw-Hill Australia CONQUERINGCHEMISTRY PRELIM MODULE 1 WS 9 gain Covalent bonding occurs when both atoms need to _______________ electrons to attain f shared noble gas configuration. When one pair of electrons is _______________ the result is a single covalent bond. g right Elements in the centre and to the _______________ of the Periodic Table tend to form covalent bonds. The number of covalent bonds an atom forms is the number of electrons _______________ that atom needs to gain to attain noble gas configuration. 2 State the number of electrons lost or gained in forming each of the following ions and state whether they are anions or cations. SYMBOL NUMBER OF ELECTRONS LOST OR GAINED Mg2+ 2 lost cation Ag+ 1 lost cation Ca2+ 2 lost cation Br– 1 gained anion O2– 2 gained anion 3 Write a formula for each of the following compounds. MgCl2 a Magnesium chloride CaO b Calcium oxide K2S c Potassium sulfide AlF3 d Aluminium fluoride 4 a b ANION OR CATION What is the ionic charge of element X in each of the following compounds? i XF 1 ii XO 2 iii X2S 1 iv X2S3 3 What is the ionic charge of Y in each of the following compounds? i MgY2 1 ii Na2Y 2 iii Li3Y 3 iv Al2Y3 2 Copyright © 2008 McGraw-Hill Australia CONQUERINGCHEMISTRY PRELIM MODULE 1 WS 9 5 6 Write the formula for each of the following compounds formed between: a boron and chlorine BCl3 b phosphorus and iodine PI3 c hydrogen and bromine HBr d nitrogen and oxygen N2O3 or NO2 Draw Lewis electron dot structures for the following molecules. a e H2 ���� b ��� f HCl g NH3 ��������� � d Mg2 Mg � ���� c O2 F ��� K K 7 8 Write ionic equations showing the formation of ions from the following neutral elements. a Potassium K → K e b Strontium Sr → Sr2 2e c Aluminium Al → Al3 3e d Iodine I e → I e Sulphur S 2e → S2 f Nitrogen N 3e → N3 Classify the following statements as true (T) or false (F). For those statements that are false, alter them to be correct. a A molecule must contain two different elements joined together. FALSE b A molecule must contain two OR MORE ATOMS joined together. Elements tend to undergo chemical reactions to form compounds in order for their atoms to obtain noble gas configuration. TRUE c The formula for hydrogen gas is H. FALSE d The noble gases exist as diatomic molecules. FALSE e The formula for hydrogen gas is H2. The noble gases exist as MONOATOMIC molecules. Elements in the same group will always form the same number of covalent bonds. TRUE Copyright © 2008 McGraw-Hill Australia CONQUERINGCHEMISTRY PRELIM MODULE 1 WS 9